JPH02293285A - Intake system for motorocycle - Google Patents

Abstract

PURPOSE:To extend the degree of freedom from the forming standpoint of a connecting duct by setting up a fuel supply system so as to have height of the venturi passage situated in and around the bottom of a crankcase and to cause an inlet port to be directed to the front of a vehicle, then connecting a discharge port to an intake opening formed in the bottom of the crankcase. CONSTITUTION:Air inhaled in an air cleaner 21 from a fresh-air intake pipe 21b is inhaled in a carburetor 20 (fuel system) by way of symmetrical branch ducts 22b and a surge tank 25 after being filtered by an element, hereat it comes a mixture with gasoline and is fed to the inside of a crankcase 11a by suction. An intake opening 11b at the side of an engine is formed in and around the bottom of the crankcase 11a, and since the carburetor 20 is set up in a deeper spot than the bottom of a crankcase 11 and connected to the intake opening 11b on the bottom, an interval between the carburetor 20 and a front-wheel rear edge becomes widened, so that thickness in the longitudinal direction of a part of the surge tank 25 of a connecting duct 22 is sufficiently securable, thus a problem of restriction from the forming standpoint of this connecting duct 22 is no longer caused there.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention provides an air intake system for supplying clean air filtered by an air cleaner to a two-stroke engine of a motorcycle.
In particular, when a fuel supply device such as a carburetor or fuel injection device is connected to the front side of the engine,
Fuel supply device. Concerning improvement of air cleaner connection structure. [Prior Art] Modern motorcycles have a so-called front air intake system in which the carburetor is connected to the front wall of the engine and the exhaust pipe is connected to the rear wall of the engine. There is a rear exhaust system. This Akio motorcycle was developed for competition use, in which the motorcycle runs at high speed within a predetermined course, and the intake system of this competition motorcycle is equipped with an air cleaner to reduce intake resistance as much as possible and improve output. The vaporizer is configured so that outside air is directly sucked into the vaporizer without providing a
(See No. 815). [Problems to be solved by the invention] By the way, the above-mentioned front intake. In order to apply the rear exhaust system to commercially available motorcycles for public roads, it is necessary to supply clean air filtered by an air cleaner to the engine in order to ensure the durability of the engine. In this case, it is necessary to adopt an appropriate intake system according to the special structure in which the fuel supply system is connected to the front side of the engine. For example, depending on the location of the carburetor, the ventilation port of the carburetor may be located close to the rear edge of the front wheel, which may narrow the space for installing the connecting tally connecting the carburetor and the air cleaner. Due to shape constraints, such as the need to make the carburetor connection part small in diameter, there is a concern that the flow of intake air may be hindered as a result. Therefore, in view of the above situation, the present invention has been developed to provide front air intake for commercially available vehicles.
When adopting the rear exhaust system, the space between the intake port of the fuel supply system and the rear edge of the front wheel can be widened, and the degree of freedom in the shape of the connecting duct for the fuel supply system can be expanded. The purpose is to provide intake devices for motorcycles. [Means for Solving the Problems] The present invention provides an intake system for a motorcycle in which an exhaust pipe is connected to the rear wall of the engine, in which the fuel supply system is arranged such that the height of the venturi path is near the bottom of the crankcase. Located in
In addition, the intake port is arranged so as to face the front of the vehicle, and
The engine is characterized in that the discharge port is connected to an intake opening formed at the bottom of the crank chamber, and an air cleaner located at the upper front side of the engine is connected to the intake opening via a connecting duct. Here, the fuel supply system of the present invention includes both a normal carburetor and a fuel injection system in which a fuel injection valve A and a throttle valve are arranged in a Henchuri pipe. [Function] According to the intake device according to the present invention, since the intake opening is formed at the bottom of the crank chamber, the intake opening is located at the rear compared to a case where the intake opening is formed at the front part of the cylinder body or the crank chamber. Therefore, the fuel supply system can be placed closer to the rear of the vehicle as the intake opening is located at the rear. This allows the intake port of the fuel supply device to be positioned further back from the rear edge of the front wheel to expand the space between the two, and as a result, the shape of the connecting duct near the connection part of the fuel supply device The above-mentioned problem of being restricted by the narrow space between the front wheel and the rear edge of the front wheel is eliminated, and the degree of freedom in the shape of the connecting duct to the fuel supply device can be expanded. [Example] Hereinafter, the present invention An example of this will be explained with reference to the figure. 1 to 3 are diagrams for explaining an intake system for a motorcycle according to an embodiment of the present invention. In the figure, reference numeral 1 denotes a motorcycle in which the device of this embodiment is adopted, and its body frame 2 has left and right (hereinafter referred to as front, rear, left, and right) extending obliquely downward from the head pipe 2a at the front end to the rear of the vehicle body. (all cases are when facing the front of the vehicle) A pair of main frames 2b
A rear arm bracket 2C is integrally formed at the rear end of the rear arm, and both brackets 2C are connected by a cross pipe 2d. A front fork 4, which pivotally supports the front transport 3 at its lower end, is supported by the hesode pipe 2a so as to be steerable left and right, and a left-right split type steering handle 4a is fixed to the upper end of the front fork 4. It has been done. Further, the rear arm 6, which pivotally supports the rear arm 5 at its rear end, is pivotally supported by the rear arm bracket 2C so as to be able to swing up and down. Also, on the upper side of the vehicle body frame 2, from the front, fuel tanks 7. Sheet 8 is placed, and the left side of sheet 8 is placed. The right side and rear side are covered with a side cover 9a. Furthermore, the left side of the vehicle body frame 2. The right side and lower part are surrounded by a cowling 9, and the engine unit l is enclosed within the factory cowling 9.
O is suspended and supported. This engine unit 10 is of a water-cooled two-stroke parallel two-cylinder type, and has a cylinder body 12 and a cylinder head 13 mounted in a forward-inclined state on the front part of a mud wall of a crankcase 1L integrated with a transmission case. Attach the above crankcase 11 with the head bolt 14.
The structure has been concluded with the following. The rear wall of the above cylinder body l2 has a left side. Right pair of exhaust ports 12a. 12a is formed, and the cough left. The right exhaust port 12a, 12a has a left exhaust port. The front ends of the right pair of exhaust pipes 15.15 are connected. Each exhaust pipe 15 is shown on the left above. It extends obliquely upward from the inside of the right main frame 2b through the inside of the side cover 93 to the rear end of the vehicle. Also, a left cylinder is inserted into each cylinder of the cylinder body 12. The right piston 16 is located in the crankcase 11
It is connected via connecting rods 18 to left and right crank arms 17a of a crankshaft 17 disposed at the front of the engine. Each crank arm 17a is
They are located in the left and right crank chambers 11a that are integrally formed within the crankcase l1. Note that 12b is an exhaust timing control device. Further, intake openings 1 lb are formed at the bottoms of the left and right crank chambers 11a, respectively.
lb is integrally formed with an intake pipe portion 11C extending downward at an angle of about 60 degrees with respect to the horizontal plane. A discharge port 20b, which is an opening on the downstream side of the carburetor 20, is connected to each intake pipe portion 1lc via an elbow-shaped hard rubber carburetor joint 19 with both end faces having an angle of 60 degrees. Therefore, in each carburetor 20, the axis of the bench passage 20c is substantially horizontal and is located below the bottom surface of the crankcase 11, and the intake port 20a, which is the upstream opening, faces the front of the vehicle. Note that 27 is a reed valve that prevents the Y-fuel mixture from blowing back from inside the crank chamber 11a and adjusts the amount of air-fuel mixture. Also, the above left. To 7 between the right main frames 2b and 2b
Near the pipe 2a and on the bottom wall 7b of the fuel tank 7
The air cleaner 2 is placed in the space 7a formed by expanding the air cleaner 2 upward.
1 are arranged at the upper part of the left and right side walls and the upper wall of the air cleaner 2l. The rear wall is covered with a fuel tank 7, and the lower portions of the left and right walls are covered with the left and right main frames 2b.

This air cleaner 21 is of a type that is divided into an upper part and a lower part, and an outside air intake pipe 2lb is connected to the side wall of the upper case 21a, and a connecting pipe part 21d is integrally formed on the bottom wall of the lower case 21C. ．． An upper end portion 22a of the connecting duct 22 is connected to the connecting pipe portion 21d via a rubber joint 23. This connecting duct 22 is made of resin and is integrally molded by blow molding, and is connected to left and right branch ducts }22b from the upper end 22a.
, 22c, extending downward while expanding to the left and right. Both branch ducts 22b and 22c are formed to have a diameter sufficiently larger than the diameter of the venturi passage 20c of the carburetor 20, and near the center in the height direction of both branch ducts 22b and 22c, there is a A curved portion 22d that is concave toward the rear is formed. Furthermore, near the center in the height direction of this curved portion 22d, a constricted portion 22e is formed which is smaller in diameter than other portions and has a diameter slightly larger than or the same as the diameter of the venturi passage 20c. Further, the lower portions of both branch ducts 22b and 22c are connected to each other, and the connecting portion is connected to the left side. The surge tank 25 is common to the right side. When this connecting duct 22 is viewed as a whole from the front of the vehicle, it has a ring shape with an opening 22g in the center, and the upper part of the cylinder body 12 and the cylinder head l3 face forward from this opening 22g. In addition, a radiator 24 is located in front of and above the cylinder hand l3. It is arranged so as to straddle the lower part of the right main frame 2b. This radiator 24 has a core portion 24a that is curved in a convex manner toward the rear of the vehicle in order to avoid interference with the front cover 3 and to expand the area of wind blowing.
To the left of The head tank part 24b is connected to the right side,
Most of it is located within the curved portion 22d of the connecting duct 22. The bracket 24C fixed to the core part 24a is fixed to the bracket 2e on the lower surface of the left and right main frames 2b, and the bracket 24d fixed to the rear surface of the hesod tank part 24b is connected to the main frame 2b via the stay 28. It is fixed to the engine support bracket 2f. The stay 28 is connected to the connecting duct 22.
It extends rearward so as to be in contact with the outer surface of the constricted part 2211. Although not shown, the radiator 24 is connected to a circulation pump disposed in the crankcase 11 and a cylinder head l3 through a cooling water hose. The surge tank 25 is located on the left side of the cowling 9. right wall 9
Bracket 25
It is fixed to the vaporizer 20 as shown in e. Further, the front wall 25a of the surge tank 25 opposes the rear green of the front cover 3 with the front wall 9C of the cowling 9 interposed therebetween. Further, a pair of left and right connection openings 25c are formed in the rear wall 25b of this surge tank 25.
The front end of the joint 26 is fitted and connected to. The rear end of the inlet 26 is fitted and connected to the intake port 20a of the carburetor 20, and is fixed with a fixing band 27a. Next, the effects of this embodiment will be explained. In the intake system of this embodiment, from the outside air intake pipe 2lb to the air cleaner 2I
The air sucked into the interior is filtered by an element and then sent to the left and right branch ducts 22b, 22c, and the surge tank 2.
5 and is sucked into the carburetor 20, where it becomes a mixture with gasoline and is sucked and supplied into the crank chamber 11a. Since the carburetor 20 and the air cleaner 21 are connected through the connecting duct 22 in this way, clean air can be supplied to the carburetor 20 connected to the front side of the engine. On the other hand, as mentioned above,
In the front intake system, depending on the arrangement of the carburetor, the gap between the intake port of the carburetor and the rear edge of the front wheel becomes narrow, and there is a concern that the carburetor connecting portion of the connecting duct may be subject to shape constraints. In contrast, in this embodiment, the intake opening 11a on the engine side is formed near the bottom of the crank chamber 11a, and the carburetor 20 is placed lower than the bottom of the crankcase 11 and connected to the intake opening 11a at the bottom. Therefore, the carburetor can be moved to the rear compared to when it is connected to the cylinder body or the front wall of the crank chamber. As a result, the distance between the carburetor 20 and the rear edge of the front wheel is widened, and the surge tank 25 portion of the connecting duct 22 can have a sufficient thickness in the longitudinal direction, so that the problem of the above-mentioned shape restriction does not occur. Also,
Since the connecting duct 22 is formed relatively long in the vertical direction, a sufficient volume of the connecting duct 22, that is, a volume on the secondary side of the air cleaner, can be secured, and the branch ducts 22b and 22c can be connected to each other to prevent surge. Since the tank 25 is configured, sufficient tank capacity can be secured, and from these points, the response of intake air can be greatly improved. If the branch ducts 22b and 22c are made longer, there is a concern that the intake efficiency will decrease due to vibration of the intake air column.
In this embodiment, since the constricted portion 22e is formed in the middle of both the branch ducts 22b and 22C, the above-mentioned air column vibration can be suppressed and a decrease in intake efficiency can be avoided. Furthermore, the constricted portion 226 can be used as a space for arranging the radiator stay 28, and the stay 28 can be prevented from protruding outward.
In addition, in this embodiment, the air cleaner 21 is placed in a relatively wide space between the left and right main frames 2b, 2b, so that sufficient air cleaner capacity can be secured, and since the air cleaner 21 is located at a high place, the above-mentioned There is no concern that muddy water, etc. will be sucked in from the 2lb outside air intake pipe. Furthermore, regarding maintainability such as element replacement, since the air cleaner 21 is exposed by removing the fuel tank 7, it can be easily replaced and maintainability can be ensured. In the above embodiment, the air cleaner was placed between the left and right main frames 2b, but the position of the air cleaner is not limited to between the main frames.
For example, in the case of an air-cooled engine, it can be placed in the radiator placement space of the above embodiment. Further, in the above embodiment, the connecting duct 22 that connects the carburetor 20 and the air cleaner 21 is branched into two, but in the present invention, the duct does not necessarily need to be branched, and may be connected with one duct. ．． Further, in the above embodiment, a surge tank was provided between the lower parts of the branch ducts, but in the present invention, this surge tank is not necessarily necessary, and since the duct volume can be secured sufficiently as described above, this surge tank is not required. Intake response can be improved even without providing one. [Effects of the Invention] As described above, according to the intake device for a motorcycle according to the present invention, the intake opening is formed at the bottom of the crank chamber, and the fuel supply device is installed at a height near the bottom of the crankcase and at a height near the bottom of the crankcase. Since the side is arranged facing forward and connected to the intake opening, the fuel supply device 1 can be moved to the rear, and the distance between the intake port of the fuel supply device and the rear edge of the front wheel is widened, and the fuel supply device of the connecting duct can be moved to the rear. This has the effect of expanding the degree of freedom in the shape of the connected part.

[Brief explanation of drawings]

[Figures 3 to 3 are diagrams for explaining an intake system for a motorcycle according to an embodiment of the present invention, in which Figure 1 is a left side view, Figure 2 is a front view of a connecting duct section, and Figure 3 is a front view of a connecting duct portion. The figure is a left side view of a motorcycle in which the device of this embodiment is adopted. In the figure, ■ is a motorcycle, l1 is a crankcase,
Ila is a crank chamber, Ilb is an intake opening, 12 is a cylinder body, l5 is an exhaust pipe, 20 is a carburetor (fuel supply device), 20a is an intake port, 20b is a discharge port, 2l is an air cleaner, and 22 is a connecting duct. ．． Patent Applicant Yamaha Motor Co., Ltd. Agent Patent Attorney Tsutomu Shimoichi IN

Claims (1)

[Claims] (1) In a motorcycle having an exhaust pipe connected to the rear wall of a two-stroke engine, an intake device for supplying clean air to the engine, the fuel supply device being connected to the crankcase with a venturi passage located at the height of the fuel supply device. The engine is located near the bottom of the engine, with the intake port facing the front of the vehicle, and the discharge port is connected to the intake opening formed at the bottom of the crank chamber, and is further connected to the air cleaner located at the top of the front of the engine. An air intake device for a motorcycle, characterized in that it is connected to the air intake port via a duct.