JPH0710457U - Intake pipe for 2-cylinder engine - Google Patents

Abstract

(57) [Abstract] [Purpose] To improve fuel distributability in an intake pipe that distributes and supplies fuel to a first cylinder and a second cylinder from a single fuel supply device. [Structure] Opening 1 of intake passage 1 connected to fuel supply device C
At the inner bottom portion F2 of the intake pipe F facing A, the opening 1 of the intake passage 1 is formed.
The columnar protrusion 4 protruding toward A is provided, and the upper end surface 4A of the columnar protrusion 4 is opposed to the opening 1A of the suction passage 1.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an intake pipe for supplying fuel supplied from a fuel supply device to a cylinder of an engine, in which fuel supplied from a single fuel supply device to the intake pipe is first intake air of the intake pipe. The present invention relates to an intake pipe for a so-called one-carburetor two-cylinder machine, which is distributed and supplied from a passage to a first cylinder of an engine and is distributed and supplied from a second suction passage to a second cylinder of an engine.

[0002]

[Prior art]

 A conventional intake pipe for a two-cylinder engine is shown in FIG. Referring to FIG. 3, C is a fuel supply device including a carburetor, and H is an intake pipe that distributes and supplies the fuel supplied from the fuel supply device C to each cylinder of the engine. The carburetor as the fuel supply device C has the following configuration. Reference numeral 10 denotes a carburetor main body in which an intake passage 11 penetrates vertically and a throttle valve 13 is rotatably arranged below a venturi portion 12 to control opening / closing of an effective opening area of the intake passage 11. A float chamber 14 is formed on the side of the main body 10, and a constant fuel liquid level is formed in the float chamber. Reference numeral 15 is a main nozzle that opens into the venturi portion 12, and the main nozzle is immersed below the constant fuel liquid level in the float chamber 14 via the mixing pipe 16 and the main fuel jet 17. The intake pipe M has an intake passage 20 that opens upward, and a first intake passage 21 that extends toward one side (rightward in the drawing) in a substantially horizontal direction from the intake passage 20 and that is connected to a first cylinder (not shown) of the engine. And a second intake passage 22 which is connected to a second cylinder (not shown) of the engine and extends to the other side (left side in the drawing) in the substantially horizontal direction from the intake passage 20, and the intake passage 20 of the intake pipe M is A connection opening is made in the intake passage 11 of the fuel injection device C. When the engine is operated and a negative pressure is generated in the intake pipe M, fuel is sucked into the intake passage 11 from the main nozzle 15, and the fuel flows down into the intake passage 20 of the intake pipe M. A part of the fuel in the intake passage 20 is supplied to the first cylinder of the engine via the first intake passage 21, while the other part of the fuel in the intake passage 20 is supplied to the first cylinder of the engine via the second intake passage 22. It is supplied to two cylinders. In the intake pipe M, in order to equalize the amount of fuel distributed in other words to the first cylinder and the second cylinder (in other words, the amount of air-fuel mixture), the partition wall 30 facing the intake passage 20 at the bottom of the intake pipe M. Alternatively, a mountain-shaped protrusion 31 is provided.

[0003]

[Problems to be solved by the device]

 According to such a conventional intake pipe for a two-cylinder engine, a part of the fuel flowing into the intake pipe M from the intake passage 20 is partially divided into the first intake passage 21 and the second intake passage by the partition wall 30 or the mountain-shaped protrusion 31. It is distributed to the passages 22 and is supplied to each cylinder connected to each intake passage, but it is difficult to supply fuel uniformly to each cylinder. This will be described based on the experimental results of FIG. The mixing ratio of fuel and air for each cylinder was determined by an exhaust gas analysis method which was found by measuring the concentration of carbon monoxide (CO%) contained in the exhaust gas of each cylinder. According to FIG. 4, the inter-cylinder variation between the first cylinder and the second cylinder in each operating state is from CO concentration of 1.6% to 3.7%, and the average inter-cylinder variation is 2.95%. The maximum variation between cylinders reaches 3.7%. The large inter-cylinder variation between the first cylinder and the second cylinder indicates that the partition wall 30 or the mountain-shaped projection 31 provided for suppressing the inter-cylinder variation does not work effectively. is there. That is, the fuel flowing into the intake pipe M from the intake passage 20 is divided into the first intake passage 21 and the second intake passage 22 in the intake pipe M1 immediately below the intake passage 20. Since the volume of the intake pipe M1 immediately below 20 is large, the fuel flow velocity is greatly reduced and sufficient fuel diffusion cannot be performed, which causes a drift in the intake passage on one side. It is thought to be due to this.

The intake pipe for a two-cylinder engine according to the present invention has been made in view of the above problems, and an object thereof is to improve fuel distribution to the first cylinder and the second cylinder.

[0005]

[Means for solving the problem]

 The object is to open an intake passage communicating with the fuel supply device upward and to extend from the intake passage to one side to a first intake passage extending to the first cylinder of the engine and to the other side to extend to the first side of the engine. In an intake pipe for a two-cylinder engine that branches off from a second intake passage connected to two cylinders, a column-shaped protrusion that protrudes toward the opening of the intake passage is provided at the inner bottom of the intake pipe facing the opening of the intake passage. It is achieved by

[0006]

[Action]

 The fuel flowing from the intake passage into the intake pipe is divided into the first intake passage and the second intake passage from the intake pipe immediately below the intake passage. Since the columnar protrusion facing the opening of the intake passage is provided at the inner bottom of the intake pipe, the volume of the intake pipe immediately below the intake passage can be reduced. According to this, the decrease in the fuel flow velocity is suppressed, and the fuel collides with the upper end surface of the columnar protrusion at a high velocity, so that the fuel can be sufficiently diffused, and thus the first cylinder and the second cylinder can be diffused. It is possible to supply a uniform fuel.

[0007]

【Example】

 Hereinafter, an embodiment of an intake pipe for a two-cylinder engine according to the present invention will be described in detail with reference to FIGS. The same parts as those in FIG. 3 are designated by the same reference numerals and the description thereof will be omitted. FIG. 1 is a vertical cross-sectional view, and FIG. 2 is a top plan view of an intake pipe with a fuel supply device removed. The intake pipe F has an intake passage 1 that opens upward, a first intake passage 2 that extends toward one side in a substantially horizontal direction from the intake passage 1 and that is connected to the first cylinder of the engine, and a portion that is substantially horizontal in the horizontal direction from the intake passage 1. Formed by a second intake passage 3 connected to the second cylinder of the engine, the upper opening of the opening 1A of the intake passage 1 is connected to the intake passage 11 of the fuel supply device C. The lower opening of the opening 1A of the intake passage 1 opens toward the inside of the intake pipe F, and the first intake passage 2 and the second intake passage 3 extend left and right from the intake pipe F1 immediately below the intake passage 1.

A columnar projection 4 is formed on the inner bottom portion F2 of the intake pipe F facing the opening 1A of the suction passage 1 so as to project L toward the opening 1A of the suction passage 1. According to this, the upper end surface 4A of the columnar protrusion 4 faces the opening 1A of the intake passage 1, and the volume of the intake pipe F1 immediately below the intake passage 1 is reduced by the volume of the columnar protrusion 4. According to the intake pipe of the present invention having such a structure, when the engine is operated and the fuel is sucked into the intake passage 11 of the fuel supply device C, the fuel flows down the intake passage 1 of the intake pipe F and has a high speed. Collides with the upper end surface 4A of the columnar protrusion 4 protruding to the inner bottom portion F2 of the intake pipe F. The fuel colliding with the upper end surface 4A of the columnar protrusion 4 at such a high speed is because the volume of the intake pipe F1 immediately below the intake passage 1 is reduced by the columnar protrusion 4. Then, when the fuel collides with the upper end surface 4A of the columnar protrusion 4, the fuel is finely diffused and is mixed very evenly with the airflows flowing through the first intake passage 2 and the second intake passage 3, so that It is possible to evenly distribute the fuel to each cylinder connected to the intake passage. Further, since the columnar protrusion 4 is projected upward from the inner bottom portion F2, the fuel is reliably scattered toward the air flow in the intake passage at the outer peripheral end 4C of the upper end surface 4A of the columnar protrusion 4 and the intake air is absorbed. It is possible to suppress the adhesion of the pipe F to the inner wall surface, which also has an effect on uniform fuel distribution. Further, when the upper end surface 4A of the columnar protrusion 4 is made to face the entire opening 1A of the suction passage 1 (that the diameter of the columnar protrusion is close to the diameter of the suction passage 1), it flows down from the suction passage 1. Since most of the fuel to be used can be made to collide with the upper end surface 4A, the diffusion of fuel is further promoted and the effect of uniform distribution is exerted. The experimental results of the present invention are shown in FIG. 5, which shows that the CO variation between the first cylinder and the second cylinder in each operating state is from CO concentration of 1.6% to 2.0%. It can be seen that the inter-cylinder variation is 1.78% and the maximum inter-cylinder variation is 2.0%, indicating that the distribution is greatly improved compared to the conventional intake pipe.

In addition, when there is a difference in the air flow flowing through the first intake passage 2 and the second intake passage 3 in the layout of the intake pipe to the engine, the upper end surface of the columnar protrusion 4 is flattened horizontally. If the inclined surface 4B is used instead of the surface, it is possible to positively give a difference to the flow of the diffused air-fuel mixture, and to correct the air-fuel mixture flow against the difference in the air flow to achieve even distribution. You can The cross-sectional shape of the columnar projection 4, the projection size L, and the shape of the inclined surface 4B are appropriately set depending on the intake characteristics of the engine, the shape of the intake passage, and the like.

[0010]

[Effect of device]

 According to the intake pipe for the two-cylinder engine according to the present invention, the columnar protrusion 4 protruding toward the opening 1A of the intake passage 1 is provided at the inner bottom portion F2 of the intake pipe F facing the opening 1A of the intake passage 1. Since the fuel flowing down the intake passage can be made to collide with the upper end surface of the columnar protrusion in the intake pipe at a high speed, the fuel can be finely diffused, and the finer fuel can be formed on the outer peripheral edge of the upper end face of the columnar protrusion. As a result, the fuel can be mixed well into the air flow flowing through the intake passage, so a uniform fuel can be supplied to each cylinder. Moreover, since the inclined surface 4B is provided on the upper end surface 4A of the columnar protrusion 4, the fuel amount flowing to each intake passage is corrected especially when there is a difference in the flow rate of the air flowing through each intake passage. Has become possible.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of an intake pipe for a two-cylinder engine according to the present invention.

FIG. 2 is a top plan view of the intake pipe with the fuel supply device removed in FIG.

FIG. 3 is a vertical sectional view of a conventional intake pipe for a two-cylinder engine.

FIG. 4 shows variations among cylinders in various operating states in a conventional intake pipe for a two-cylinder engine.

FIG. 5 shows variations among cylinders in various operating states in the intake pipe for a two-cylinder engine of the present invention.

[Explanation of symbols]

 C fuel supply device F intake pipe 1 intake passage 1A opening 2 first intake passage 3 second intake passage 4 columnar protrusion 4A upper end surface 4B inclined surface F1 intake pipe just below the intake passage F2 inner bottom of the intake pipe F

Claims (2)

[Scope of utility model registration request] 1. An intake passage communicating with a fuel supply device is opened upward, and a first intake passage extending to one side from the intake passage and communicating with a first cylinder of the engine, and an intake passage extending to the other side of the engine. In an intake pipe for a two-cylinder engine that branches off from a second intake passage connected to the second cylinder, an inner bottom portion F2 of the intake pipe F facing the opening 1A of the intake passage 1,
An intake pipe for a two-cylinder engine, which is provided with a columnar protrusion 4 protruding toward the opening 1A of the intake passage 1. 2. The opening 1 of the suction passage 1 of the columnar protrusion 4
The intake pipe for a two-cylinder engine according to claim 1, wherein an inclined surface 4B is provided on an upper end surface 4A that faces A.