JP2001182643A - Intake passage structure of multicylinder engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an instake air passage structure capable of almost uniformly distributing fuel to respective cylinder and capable of preventing a difference in the air-fuel ratio with every cylinder. SOLUTION: A single fuel injection valve 5 capable of injecting fuel in at least three or more directions branches off on the downstream side of an installed intake air gathering part to be respectively connected to at least three or more cylinders with every cylinder, and in intake air passages 1 to 3 for supplying an air-fuel mixture of intake air and the fuel to the respective cylinders, communicating tubes 4 capable of mutually flowing the air-fuel mixture are arranged between the intake air passages 1, 3 arranged in a position where the other intake air passages do not exist on both next sides and the other intake air passage exists on one side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake passage structure for a multi-cylinder internal combustion engine, and more particularly, to each cylinder of the internal combustion engine.
The present invention relates to an intake passage structure of an internal combustion engine provided with a fuel supply device that supplies fuel from one fuel injection valve.

[0002]

2. Description of the Related Art A fuel injection system for a multi-cylinder internal combustion engine includes a system in which fuel is supplied downstream of an intake passage of each cylinder by a fuel injection valve provided for each cylinder, and a system in which a fuel injection valve is provided in an aggregate portion of the intake passage. There is a method of supplying fuel from a single fuel injection valve to the intake passage of each cylinder. Of these, a method of supplying fuel with one fuel injection valve is adopted as a method of supplying fuel at low cost.

[0003] In these, the structure of the intake passage is as follows.
For example, as disclosed in Japanese Patent Application Laid-Open No. 10-274136, it is general that the intake passages connected to the cylinders are arranged so as to be adjacent to each other in a line.

[0004]

In a system in which fuel is injected into each cylinder from a single fuel injection valve, not all of the fuel injected into the intake passage of each cylinder reaches the intake port immediately, Fuel particles are floating in the intake passage.

[0005] Of the floating fuel present in the intake passage branched downstream of the fuel injection valve, those in the vicinity of the branch portion are caused by the air flow generated when the pressure of the adjacent intake passage is reduced by the intake operation of the cylinder. The air moves from the injected intake passage toward the adjacent intake passage.

In a conventional intake passage structure, for example, in a three-cylinder four-cycle internal combustion engine, a three-cylinder branched from a collecting portion
When the two intake passages are adjacent to each other as shown in FIG. 11, when the cylinders connected to the intake passages 1 and 3 located outside are in the intake stroke, the air accompanying the decrease in the intake passage pressure is reduced. The generation of the flow causes the floating fuel to move from the adjacent central intake passage 2 to the outer intake passage.

On the other hand, with respect to the intake passage 2 located at the center, when the cylinder connected to the intake passage 2 is in the intake stroke, the intake passage 2 floats from the adjacent intake passages 1, 3 on both outer sides toward the central intake passage. The fuel will move.

FIG. 12 shows a state of movement of floating fuel in one cycle in a conventional intake passage structure. The relationship between the stroke of each cylinder and the pressure in the intake passage during one cycle is shown, and the direction of movement of the floating fuel between the cylinders is indicated by an arrow. When one cylinder connected to the outside intake passage enters the intake stroke, floating fuel flows into the one cylinder from the intake passage of the adjacent two cylinders due to the air flow due to the pressure drop. Here, the amount of movement of the floating fuel from the three cylinders that are far apart is very small and is ignored here. Similarly, when the three cylinders connected to the outer intake passage are in the intake stroke, floating fuel flows from the adjacent two cylinder intake passages toward the three cylinders.

Thereafter, when the two cylinders connected to the centrally located intake passage are in the intake stroke, the adjacent one cylinder and three cylinders are connected.
Floating fuel flows from the intake passage of the cylinder toward the two cylinders. Here, since the number of adjacent intake passages is different between the outer intake passage and the central intake passage, the amount of floating fuel flowing into the central intake passage from both outer intake passages and the central intake passage It does not match the amount of suspended fuel flowing from the passage.

As a result, as shown in FIG. 13, the air-fuel ratio of the cylinder connected to the intake passage located at the center is different from the air-fuel ratio of the cylinder connected to the intake passage located outside. Such an air-fuel ratio difference between the cylinders results in an increase in exhaust gas substances.

As described above, the conventional intake passage structure has a problem that the amount of fuel entering each cylinder is not uniform, the air-fuel ratio is shifted for each cylinder, and the amount of exhaust gas increases.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an intake passage structure capable of distributing fuel substantially evenly to each cylinder and preventing a deviation of an air-fuel ratio for each cylinder.

[0013]

In order to achieve the above object, a characteristic of an intake passage structure of a multi-cylinder engine according to the present invention is that an intake air for supplying a mixture of intake air and the fuel to each cylinder is provided. It is an object of the present invention to provide a communication pipe through which the air-fuel mixture can flow between intake passages arranged at positions where there is no other intake passage on both sides of the passage and there is another intake passage on one side.

It is another object of the present invention to configure each intake passage so that the sectional area of the intake passage at the position where each intake passage branches is larger than the sectional area of the intake passage at the position of the intake port of each intake passage. .

Specifically, the present invention provides the following intake passage structure. The present invention branches downstream from an intake manifold in which one fuel injection valve capable of injecting fuel in at least three directions is mounted, and is connected to at least three or more cylinders for each cylinder. In an intake passage structure of a multi-cylinder engine configured to supply a mixture of fuel and fuel to each of the cylinders, in the intake passage connected to each of the cylinders, there is no other intake passage on both sides and another intake passage on one side. There is provided an intake passage structure for a multi-cylinder engine, characterized in that a communication pipe through which the air-fuel mixture can flow is provided between intake passages arranged at positions where the passages are located.

Further, according to the present invention, the fuel supply device is branched downstream from an intake manifold provided with one fuel injection valve capable of injecting fuel in at least three directions and connected to at least three or more cylinders for each cylinder. In the intake passage structure of a multi-cylinder engine configured to supply a mixture of intake air and the fuel to each of the cylinders, the shape of each of the intake passages is changed by disconnecting the intake passage at the branch position of each of the intake passages. An intake passage structure for a multi-cylinder engine, wherein an area is configured to be larger than an intake passage sectional area at an intake port position of each intake passage.

Preferably, the cross-sectional area of the intake passage at the branching position is 1.5 times or more the cross-sectional area of the intake passage at the position of the intake port.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An intake passage structure according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an intake passage structure according to a first embodiment of the present invention. Reference numerals 1 to 3 denote intake passages connected to the respective cylinders, and three intake passages branched from an intake collecting portion located downstream of the fuel injection valve 5 are provided adjacently. Reference numeral 4 denotes a communication pipe provided between the intake passages 1 and 3 located on both outer sides, so that intake air can flow through each other.

FIG. 2 shows the state of movement of floating fuel in one cycle in the present intake passage structure. The floating fuel moving from one cylinder to three cylinders or from three cylinders to one cylinder through the communication pipe is shown together with the stroke diagram of one cylinder and three cylinders. When one cylinder connected to the outer intake passage 1 enters the intake stroke, floating fuel flows into the one cylinder from the communication pipe 4 connected to the adjacent two-cylinder intake passage and the three-cylinder intake passage. .

Similarly, when the three cylinders connected to the outer intake passage 3 are in the intake stroke, floating fuel is transferred to the three cylinders from the communication pipes connected to the adjacent two cylinder intake passages and the one cylinder intake passage. Inflow toward. Thereafter, when the two cylinders connected to the intake passage 2 located at the center enter the intake stroke, the floating fuel flows into the two cylinders from the intake passages of the adjacent one cylinder and three cylinders.

Here, if the amount of the floating fuel flowing from the adjacent intake passage and the amount of the floating fuel flowing through the communication pipe 4 are made equal, the amount of the floating fuel flowing in each cylinder can be made uniform. It is possible to reduce the difference in air-fuel ratio between cylinders.

Here, the length of the communication pipe 4 is longer than the distance to the adjacent intake passage, so that the ventilation resistance of the communication pipe 4 is larger than that of the adjacent intake passage. The amount of floating fuel flowing from the intake passage and the amount of floating fuel flowing through the communication pipe 4 can be made equal. Hereinafter, the reason will be described with reference to FIG.

FIG. 3 shows the pressure distribution in the intake passage. In the intake passage that is not in the intake stroke, the pressure becomes substantially constant, but the intake passage pressure at the time of the intake stroke decreases as it approaches the intake port. At the branch of the intake passage, an air flow is generated due to the pressure difference ΔP1 between the intake passage in the intake stroke and the intake passage not in the intake stroke, and the floating fuel flows from the adjacent intake pipe toward the intake pipe in the intake stroke. I do.

On the other hand, since the communication pipe 4 is provided at a position downstream of the branch portion, at the position of the communication pipe 4, the pressure difference between the pressure of the intake passage in the intake stroke and the pressure of the intake passage not in the intake stroke (communication pipe 4 The pressure difference ΔP2 between the inlet and the outlet) is larger than the pressure difference ΔP1 at the branch.

Thus, even if the ventilation resistance of the communication pipe becomes larger than the ventilation resistance of the adjacent intake passage, the communication pipe 4
Can generate the same amount of airflow as the airflow flowing from the adjacent intake passage, so that the amount of the floating fuel flowing through the communication pipe is equal to the amount of the floating fuel flowing from the adjacent intake passage. It becomes possible.

As described above, in the present intake passage structure, the floating fuel can be moved between both outer intake passages that are not adjacent to each other. Therefore, all the cylinders flow from the intake passages of the other cylinders in the intake stroke. The amount of floating fuel to be used can be equalized. Therefore, when determining the optimum position of the communication pipe 4, the position of the communication pipe 4 may be gradually shifted downstream from the branch portion so that the air-fuel ratio between cylinders is minimized.

FIG. 4 shows the measurement results of the air-fuel ratio between cylinders according to the intake passage structure. The difference in air-fuel ratio between cylinders can be reduced as compared with the case where there is no communication pipe.

FIG. 5 shows an example in which the present intake passage structure is applied to a four-cylinder internal combustion engine. The communication pipe 4 is provided between the intake passages on both outer sides of the four adjacent intake passages.

FIG. 6 shows the state of movement of the floating fuel when a communication pipe is provided in the intake passage of a four-cylinder internal combustion engine.
Here, if the amount of the floating fuel flowing from the adjacent intake passage is equal to the amount of the floating fuel flowing through the communication pipe, the amount of the floating fuel flowing in each cylinder is made uniform as in the case of the three cylinders. It is possible to reduce the difference in air-fuel ratio between cylinders.

FIG. 7 shows, as a comparative example of FIG. 6, the state of movement of floating fuel in a four-cylinder internal combustion engine in which no communication pipe is provided between the intake passages on both outer sides. When the intake passages of the two or three cylinders located inside are in the intake stroke, floating fuel flows in from the two intake passages on both sides. On the other hand, when the intake passages of the one and four cylinders located on both outer sides are in the intake stroke, since the communication pipe is not provided, the floating fuel flows only from one adjacent intake passage.

Therefore, since the number of adjacent intake passages is different between the outer intake passage and the inner intake passage, the amount of floating fuel flowing into the inner intake passage is reduced by the amount of floating fuel flowing into the outer intake passage. It does not match the amount of fuel, resulting in an air-fuel ratio difference between cylinders.

FIG. 8 shows an intake passage structure according to a second embodiment of the present invention. As shown in FIG. 8, the intake passage 6 at the branch position of the intake passage 6 is configured to be larger than the intake passage sectional area at the intake port position of the internal combustion engine. The state of the floating fuel in the intake passage structure will be described with reference to FIG.

FIG. 9 is a side view of the present intake passage, which is shown together with a conventional intake passage shape. Floating fuel exists along the central axis of the injection direction, and decreases as the distance from the central axis increases. Therefore, in the intake passage of the second embodiment in which the passage cross-sectional area of the branch portion is enlarged as compared with the conventional intake passage, the average concentration of floating fuel near the branch portion can be reduced.

On the other hand, the volume of air flowing from the intake passage adjacent to the intake passage in the intake stroke is substantially the same as that of the conventional intake passage. Therefore, the amount of the floating fuel flowing from the intake passage adjacent to the intake passage in the intake stroke can be made smaller than that of the conventional intake passage by the decrease in the concentration of the floating fuel in the branch portion.

Thus, as shown in FIG. 10, the cylinder-to-cylinder difference of the air-fuel ratio is reduced as the passage area ratio (intake passage sectional area at branch position / intake passage sectional area at intake port position) R is increased. Can be. In the example of the test engine, when the passage area ratio R is 1.5 times or more, the inter-cylinder difference in the air-fuel ratio can be reduced.

[0037]

According to the present invention, by providing a communication pipe between both outer intake passages through which intake air can flow, the amount of floating fuel flowing from another intake passage for each cylinder can be reduced. Since they can be made substantially equal, the difference in air-fuel ratio between cylinders can be reduced, and the amount of exhaust gas substances can be reduced.

By configuring each intake passage sectional area at the branch position to be larger than each intake passage sectional area at the intake port position, the amount of floating fuel flowing from another intake passage for each cylinder is reduced. Since the air-fuel ratio can be reduced, a difference in air-fuel ratio between cylinders can be reduced, and exhaust gas substances can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing an intake passage structure according to a first embodiment of the present invention.

FIG. 2 is a view showing a moving state of floating fuel in the intake passage structure of FIG.

FIG. 3 is a diagram showing a pressure distribution in an intake passage of FIG. 1;

FIG. 4 is a diagram showing a measurement result of an air-fuel ratio between cylinders in the intake passage structure of FIG. 1;

FIG. 5 is a diagram showing an example in which the intake passage structure of FIG. 1 is applied to a four-cylinder internal combustion engine.

6 is a diagram showing a state of movement of floating fuel in an intake passage of the intake passage structure shown in FIG. 5;

FIG. 7 is a diagram showing a comparative example with FIG. 6;

FIG. 8 is a diagram showing an intake passage structure according to a second embodiment of the present invention.

9 is a diagram showing a distribution of floating fuel in the intake passage structure of FIG.

FIG. 10 is a diagram showing a measurement result of an inter-cylinder difference of an air-fuel ratio by the intake passage structure of FIG. 8;

FIG. 11 is a view showing a conventional intake passage structure.

FIG. 12 is a diagram showing a moving state of floating fuel in a conventional intake passage structure.

FIG. 13 is a diagram showing a difference between cylinders of an air-fuel ratio in a conventional intake passage structure.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... intake passage (outside), 2 ... intake passage (center), 3 ... intake passage (outside), 4 ... communication pipe, 5 ... fuel injection valve, 6 ... intake passage

Claims (3)

[Claims] The present invention is characterized in that it branches downstream from an intake manifold provided with one fuel injection valve capable of injecting fuel in at least three directions and is connected to at least three or more cylinders for each cylinder. In the intake passage structure of the multi-cylinder engine configured to supply the mixture with the fuel to each of the cylinders, in the intake passage connected to each of the cylinders, there is no other intake passage on both sides and another on one side. An intake passage structure for a multi-cylinder engine, wherein a communication pipe through which the air-fuel mixture can flow is provided between intake passages arranged at a position where the intake passage is located. 2. A fuel supply system comprising a fuel injection valve which is capable of injecting fuel in at least three directions. The fuel injection valve is branched downstream from an intake manifold and connected to at least three or more cylinders for each cylinder. In the intake passage structure of the multi-cylinder engine configured to supply the mixture with the fuel to each of the cylinders, the shape of each of the intake passages is such that the intake passage cross-sectional area at the branching position of each of the intake passages is An intake passage structure for a multi-cylinder engine, wherein the intake passage structure is configured to be larger than an intake passage cross-sectional area at an intake port position of each intake passage. 3. The intake passage according to claim 2, wherein the sectional area of the intake passage at the branching position is 1.5 times or more the sectional area of the intake passage at the position of the intake port. The intake passage structure of a multi-cylinder engine.