JP3332177B2 - Spark ignition internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a spark ignition type internal combustion engine in which an air-fuel ratio is reduced according to operating conditions.

[0002]

2. Description of the Related Art In a spark ignition type internal combustion engine, a swirl control valve provided with a partial opening such as a notch is provided mainly for the purpose of improving the combustion characteristics during low load operation or lean air-fuel ratio operation. A known air control valve is installed in the vicinity of the engine intake port to concentrate the intake air flow at the opening to deviate the intake air in the passage and increase the flow velocity to promote the air flow in the cylinder. (See, for example, Japanese Utility Model Laid-Open No. 1-91038).

[0003]

In such a conventional internal combustion engine, the length of the branch pipe of the intake manifold and the shape of the intake passage upstream of the air control valve are generally different for each cylinder. Due to lack of vertical vortex (tumble) in the vertical direction, and the tendency of the average flow velocity of intake air to fluctuate in each cycle due to errors in the installation of air control valves in each cylinder and errors in notch shapes. However, there has been a problem that a stable lean burn operation cannot always be performed, or an air-fuel ratio for obtaining a stable operation state cannot be sufficiently increased, and a lean burn limit is low.

An object of the present invention is to solve such a conventional problem.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, according to the present invention, in a spark ignition type internal combustion engine in which the air-fuel ratio is made lean according to the operating conditions, the tumble of the intake air flow in the cylinder during the lean air-fuel ratio operation is performed. The present invention proposes an internal combustion engine in which an intake system is set such that the ratio is 1.6 to 3.1 and the swirl ratio is also 1.8 to 3.5.

However, tumble ratio = rotation speed of vertical vortex in cylinder / engine rotation speed Swirl ratio = rotation speed of horizontal vortex in cylinder / rotation speed of engine.

Further, the present invention proposes a spark ignition type internal combustion engine which is individually provided with or combined with the following means A to E as a configuration for obtaining such a tumble ratio and a swirl ratio.

A. A plurality of intake passages branching from the intake collector assembly and reaching each intake port of the engine.

B. An air control valve having a partial opening is interposed in an intake passage near an intake port. However, it is desirable that the air control valve further has the following configuration a or b.

A. At the time of lean air-fuel ratio operation, the opening side is set to be inclined downstream by a predetermined amount in a closed state, preferably within a range of 20 to 30 degrees with respect to a cross section perpendicular to the central axis of the intake passage.

B. The opening is formed in a portion above the substantially horizontal mounting shaft and offset to one side, and preferably has an angle formed by the mounting shaft center line of a line connecting the center of gravity (center of gravity) of the opening and the center of the passage. The upper part is formed to be in a range of 45 to 75 degrees or 60 to 70 degrees .

C. Air intake passage of air control valve between cylinders
And the intake air flow in a predetermined section immediately upstream of the air control valve.
The road shape should be approximately the same for each cylinder. But this intake
Regarding the passage, the following configurations c to e may be further provided.
Desirable . c. The shape of the intake passage in the predetermined section is linear. d. The intake passage for the specified section is separate from the other intake passages
Formed by a passage adapter. e. The length of the intake passage in the specified section is
Set in the range of 1.5 to 3.5 times.

D. Each intake port is formed in a shape that generates a vertical vortex in the cylinder, and especially the intake port is in contact with the engine combustion chamber.
A curved portion having a continuous curved portion and a straight portion on the upstream side thereof.
The average radius of the center line is 50 mm or more,
The angle between the center line and the horizontal plane is within the range of 10 to 30 degrees.
That .

E. Two intake valves that are driven to open with a phase difference so that the intake valve on the air control valve opening side opens earlier are provided.

On the premise of a spark ignition type internal combustion engine that dilutes the air-fuel ratio in accordance with the operating conditions, a specific combination of these means is firstly recommended as a branch from the intake collector assembly. with arranging a plurality of intake passages leading to the intake ports of the engine Te, partly during lean air-fuel ratio operation has an aperture interposed air control valve is controlled to the closed state in the vicinity of the intake ports, Each of the plurality of intake passages is
It is the same length between the cylinders, and a predetermined immediately upstream of the air control valve.
This is to make the shape of the section substantially the same between the cylinders .

Second, a lean air-fuel system having a partial opening
At the time of specific operation, the air control valve that is controlled to be closed
Interposed in the vicinity of the intake port, and the intake port is
From the curved part connected to the chamber and the straight part upstream
And the average radius of the center line of the curved portion is 5
0 mm or more, and the center line of the straight line portion forms a horizontal plane.
The angle is in the range of 10 to 30 degrees .

Third, it is located above the mounting shaft, and
Has an opening in a part that is offset in the direction
Is equipped with an air control valve that is controlled to the closed state with the intake port of the engine.
The air control valve opening side is opened early.
The two intake valves that are driven to open with a phase difference
It is prepared .

[0018]

[0019]

According to the present invention, by providing such a configuration, an optimal air flow field is formed in the cylinder, and the lean air-fuel ratio operation in a larger air-fuel ratio region can be performed without impairing the stability of combustion. It becomes possible.

Hereinafter, the operation and effect of the present invention will be described together with the experimental results of the embodiments. It should be noted that the tumble ratio and the swirl ratio are collectively referred to as "tumble swirl ratio".

[0022]

1 to 3 show an embodiment of a spark ignition type internal combustion engine according to the present invention. In each of the drawings, reference numeral 1 denotes an engine body, 2 denotes a cylinder, 3 denotes a cylinder head, 4 denotes a combustion chamber, 5 denotes a spark plug, 6 denotes an intake port, and 7 denotes an intake manifold.

As shown in FIG. 3, the intake manifold 7 has a plurality of intake pipes 9 branching from the intake collector collecting section 8 and reaching the intake ports 6 of the engine 1 having the same length and being symmetrical in the cylinder row direction. It is arranged in.

A passage adapter 10 for forming a linear intake passage of the same shape between the cylinders is provided near the joint of each intake pipe 9 with the cylinder head 3. A control valve 11 is interposed.

The air control valve 11 is rotatably supported via a mounting shaft 12 provided substantially horizontally so as to cross the passage adapter 10, and is closed through an actuator (not shown) in the lean air-fuel ratio operation. (Illustrated state).

The air control valve 11 is partially formed with an opening 13 as shown in FIG. In this case, the opening 13 is formed in such a manner that a portion deviated to one side above the mounting shaft 12 is cut out.

The air control valve 11 in the closed position is set so that the opening 13 is inclined downstream by a predetermined amount (α) as shown in FIG.

In this case, the intake port 6
It branches from the middle so as to correspond to the intake valves 14 and 15 provided individually. Further, as shown in FIG. 2, a port shape for generating a strong vertical vortex has a small angle (θ) between its center line and a horizontal plane (θ = about 10 to 30 degrees).
Is set.

In the present invention, for example, by configuring the spark ignition type internal combustion engine as described above, during the lean air-fuel ratio operation,
The tumble ratio of the intake air flow in the cylinder is set to 1.6 to 3.1, and the swirl ratio is set to 1.8 to 3.5.

The characteristics of the port shape for enhancing the tumble, that is, the vertical vortex in the cylinder, are that it has a linear shape and that the angle (θ) that the center line of the passage forms with the horizontal plane is small. In other words, the vertical air descending flow just below the intake valve on the cylinder center side in the first half of the intake stroke is suppressed as much as possible so as not to hinder the generation of longitudinal vortices in the cylinder, and the air mass flow rate above the port is increased. The stronger the tumble, the greater the strength. For example, in a certain kind of internal combustion engine for a small vehicle, it is effective that the above-mentioned θ is about 10 to 30 degrees and the radius R of the curved portion on the downstream side is 50 mm or more in order to generate a tumble.

FIG. 4 shows the length of the intake pipe (branch) of the intake manifold and the length L immediately upstream of the air control valve (see FIG. 1).
Is changed at a predetermined ratio, and the result of studying the combustion stability during lean combustion is shown. The longer the intake pipe, the smaller the relative difference in intake pipe length between the cylinders.As can be seen in the figure, the smaller the difference in intake pipe length for each cylinder, the smaller the combustion stability during lean burn. It can be seen that is improved. That is, it is a desirable condition for the intake manifold to have a stable combustion property under a lean air-fuel ratio when the intake pipe is equal in length for each cylinder.

In FIG. 4, the length of the linear portion immediately upstream of the air control valve is about 100 mm, and the combustion stability is the best. This corresponds to a length of about 2.5 times the inner diameter of the port. Actually, if the length is 1.5 to 3.5 times the inner diameter of the port, the effect of improving the stability during lean combustion can be obtained. This is because the difference in air flow for each cylinder is smoothed in the linear portion immediately upstream of the air control valve , and the air flow field for each cylinder becomes uniform.

As described above, regarding the intake system, the intake pipes to the respective cylinders of the intake manifold have the same length, and it is particularly preferable that the diameter of the port inside the port is 1.5 to 3.5 immediately upstream of the air control valve.
By providing intake passage portions having substantially the same shape and having twice the length, the air flow is made uniform among the cylinders. Specifically, the combustion stability limit air-fuel ratio value is set to about 1 to 1.5 (as a ratio). 5%) or more, an effect of improving the combustion stability during lean combustion of the engine can be expected.

FIG. 5 shows the results obtained by variously changing the position of the opening of the air control valve and examining the air-fuel ratio which becomes the stable combustion limit in lean combustion. From this figure, there is an optimum value for each of the tumble ratio indicating the strength of the vertical vortex and the swirl ratio indicating the strength of the horizontal vortex. Usually, the tumble ratio is 1.6 to 2.2 and the swirl ratio is 1. It turns out that the range of 8-3.2 is optimal. However, by increasing the output of the ignition system,
Since the chance of poor ignition decreases accordingly, the range of the optimum value is expanded, with the tumble ratio being 2.2 to 3.1 and the swirl ratio being 1.8 to 3.5.

More specifically, when the tumble ratio is strong, the generation of turbulence is large, and the generation of turbulence greatly affects the stability during lean combustion. Therefore, the same combustion stability is exhibited as shown in FIG. The line becomes nearly horizontal. On the other hand, when the tumble ratio increases, as shown in FIG. 6, the fluctuation of the average flow velocity in each cycle for the same turbulence intensity increases. When the fluctuation of the average flow velocity in each cycle becomes large, the air-fuel ratio which becomes the combustion stability limit moves in the rich direction as shown in FIG. As shown in the figure, the MPi system that injects and supplies fuel to each intake port has an average flow velocity lower than the SPi system that collectively supplies fuel for each cylinder from the upstream side of the manifold assembly. It is strongly influenced by cycle-to-cycle variations and it is therefore more important to control it. In addition, when operating at the same air-fuel ratio, the combustion stability becomes worse as the tumble ratio relatively increases. From these facts, it can be understood that the horizontal vortex in the cylinder compensates for the drawback that the vertical vortex has a large fluctuation in the average flow velocity in each cycle, and has an effect of suppressing the fluctuation of the air flow field in each cycle. .

FIG. 8 shows an optimal tumble swirl region based on such findings. From this figure, the tumble ratio is generally 1.6 to 2.8, and the swirl ratio is 1.8 to 3.2.
It can be seen that there is an optimum value in the range. However, the results in FIGS. 5 and 8 are obtained under conditions where the ignition system is not particularly strengthened. In practice, the use of a further enhanced ignition system increases the air-fuel ratio at which the stable combustion limit is reached. Even if both the tumble ratio and the swirl ratio are slightly higher, the combustion is stable.

The enhancement of the ignition system is to increase the discharge period of the discharge voltage and increase the discharge energy. For this purpose, it is generally necessary to improve the ignition coil and the durability of the ignition plug to withstand a large discharge energy. However, excessive strengthening of the ignition system consumes engine power for driving energy of the ignition coil, thereby deteriorating fuel consumption and promoting consumption of the spark plug. Therefore, there is a certain limit to strengthening the ignition system.

FIG. 9 shows a stable combustion limit with respect to the tumble ratio and the swirl ratio in the ignition system reinforced at a practically acceptable level. The optimum tumble ratio is 2.7 and the swirl ratio is 2.7. As described above, the tumble ratio is 2.2 to 3.1, and the swirl ratio is 1.8 to 3.5.
The combustion improvement effect can be seen in the range.

Next, the effect of the position of the center of gravity of the opening of the air control valve on combustion stability will be described. FIG. 10 shows air
4 shows the relationship between the position of the center of gravity of the control valve opening and the stable combustion limit air-fuel ratio during lean combustion. There is an optimum value for the position of the center of gravity of the opening of the air control valve, and if it is assumed that an effect of about 95% of the optimum value is obtained in consideration of manufacturing errors and differences in engine specifications, the center of gravity of the opening from the passage center. It is necessary that the angle (β) between the line drawn at the point and the mounting axis is in the range of 45 to 70 degrees, and preferably β is about 50 to 55 degrees. By the combination of this opening configuration and the intake port (tumble enhancement port) that generates the above-described tumble, the above-described tumble ratio = 2.7 and swirl ratio =
It is possible to obtain an optimum value of 2.7.

Although it is possible to generate a tumble only with the air control valve provided with the opening without using the tumble reinforcing port together, it is generally better to use the tumble reinforcing port together with the opening area of the air control valve. You can get
The advantage is obtained that the lean burn operation can be performed up to a higher load range.

Next, the setting of the upper portion of the air control valve so as to be inclined by a predetermined amount toward the downstream side of the flow in the closed position will be described. This improves the combustion stabilizing effect as shown in FIG. This is, as shown in FIG.
Generation of turbulence by the air control valve inclination is intact, the air system
This is because the flow of the intake air to the valve opening is adjusted, and the cycle fluctuation of the average deceleration is suppressed. FIG. 13 shows the air control.
It shows the relationship between the valve inclination angle (α) and the stable combustion effect. As shown, the air control valve inclination angle 20-3
0 degree is the range in which improvement in combustion stability can be expected most.
When the inclination angle is around 0 degree, the range of the air- fuel ratio that can be set becomes small due to the mounting variation. However, by setting the inclination angle of the air control valve in the range of 20 to 30 degrees, the width of the air-fuel ratio that can be set is set. Is maximized, and therefore, even if there is an error in mounting the inclination angle, this can be sufficiently absorbed.

On the other hand, in the case of an engine provided with two intake valves as shown in FIG. 1 or FIG. 2, the intake valve (the intake valve 15 in FIG. 1) facing the air control valve opening is set to be smaller than the other. By opening the valve at an early stage, the combustion stability can be improved as shown in FIG. This is, air control
By opening the intake valve on the valve opening side first, a trigger for swirl tumble generation of one intake port corresponding to the intake valve can be stably obtained, and as a result, as shown in FIG. As described above, the fluctuation of the average flow velocity in each cycle is suppressed while generating the turbulence as it is.

As described above, according to the present invention, the optimum lean burn operation performance is obtained by setting both the tumble ratio and the swirl ratio to around 2.7, and such setting of the tumble swirl ratio is realized. As a specific configuration, the intake manifold structure is made equal length and symmetrical, an air control valve having an opening at a predetermined position, and setting of the mounting inclination angle thereof,
Means such as a tumble strengthening port of the intake port and setting of a phase difference valve opening of the two intake valves are proposed. However, each of the above means is merely an example of the configuration, and even if other configurations are adopted, the above-described means is not required. By setting the optimum tumble swirl ratio of the present invention, it is possible to expect an effect of expanding the lean burn limit or improving the stability of the lean burn engine.

In carrying out the above-mentioned means, it is not always necessary to combine all of them in accordance with the required specifications of the engine. For example, in a long stroke type engine having a bore / stroke ratio of about 0.8 to 0.9,
The piston speed is high need not necessarily be the intake port and the tumble reinforcing port, and optimizing the inclination angle α and the air control valve opening centroid angle β of the above described air control valve, by setting the phase difference of the intake 2 valves It is possible to realize an optimum tumble swirl ratio. However, in this case, the air control only
It is desirable to enhance tumble generation at the orifice opening,
For this purpose, for example, the center of gravity angle β is set to be in a range of 60 to 70 degrees as shown by a reference symbol S in FIG. The phase difference between the two intake valves is, for example, about 8 degrees as a crank angle as shown in FIG.

FIG. 16 shows the effect of each of the above-described means for embodying the present invention and some combinations thereof as a combustion limit air-fuel ratio. As shown in the figure, as compared with a conventional example in which an air control valve is merely provided in an engine of a two-intake type, the tumble reinforced port (the means D of the present invention described above), the air control valve is inclinedly mounted (similarly, a ), Empty
Even if the intake system is made equal length and symmetrical including the same linear shape immediately before the air control valve (same means A and C), the phase difference valve opening setting of the two intake valves (same means E), etc. The combustion limit improving effect can be obtained. In particular, by combining them and setting the position of the center of gravity of the air control valve opening optimally (same means b), reference numerals 5, 9, 10 in the figure are used.
A remarkable effect can be obtained as shown in the graph of FIG. Further, when a phase difference is given to the two intake valves, a sufficiently excellent combustion improvement effect can be obtained even in a configuration without a tumble enhancement port as indicated by reference numeral 11.

[0046]

In summary, the present invention relates to a spark-ignition internal combustion engine which stabilizes combustion during lean combustion by ensuring appropriate turbulence due to a tumble component in a cylinder and suppressing cycle fluctuations of an average flow velocity due to a swirl component. While giving the optimal tumble ratio and swirl ratio based on the knowledge that an effective air flow field in the cylinder can be obtained,
Specific means for realizing this include: making the intake pipe configuration isometric and symmetric, optimizing the position of the center of gravity of the opening of the air control valve, optimizing the inclination mounting angle of the air control valve, the shape of the tumble reinforced port, It proposes a configuration such as a two-valve intake valve that opens with a phase difference. By providing these configurations, the lean burn limit is further improved, or the combustion stability in the lean burn region is improved. This has the effect of being able to do so.

[Brief description of the drawings]

FIG. 1 is a schematic plan sectional view of one embodiment of a spark ignition type internal combustion engine according to the present invention.

FIG. 2 is a schematic longitudinal sectional view of the embodiment.

FIG. 3 is a schematic plan view showing the configuration of the intake manifold of the embodiment.

FIG. 4 is a diagram showing a relationship between a size of an intake pipe and a stable combustion limit.

FIG. 5 is a diagram showing a relationship between a tumble ratio and a swirl ratio of intake air and a stable combustion limit.

FIG. 6 is a diagram showing a relationship between a tumble ratio component of intake air and a cycle variation of an average flow velocity.

FIG. 7 is a diagram showing a relationship between a cycle variation of an average flow velocity of intake air and a stable combustion limit.

FIG. 8 is an explanatory diagram showing a relationship between an opening configuration of the air control valve and a tumble swirl region.

FIG. 9 is an explanatory diagram showing an optimum tumble swirl region in relation to a stable combustion limit.

FIG. 10 is an explanatory diagram showing a relationship between an opening center-of-gravity angle of the air control valve and a stable combustion limit.

FIG. 11 is an explanatory diagram of the combustion improvement effect based on the setting of the inclination angle of the air control valve.

FIG. 12 is a diagram showing a relationship between the inclination angle of the air control valve and the cycle fluctuation of the average flow velocity of intake air.

FIG. 13 is a diagram showing the relationship between the inclination angle of the air control valve and the stable combustion limit for each inclination angle.

FIG. 14 is an explanatory diagram of a combustion improvement effect when two intake valves are opened with a phase difference provided therebetween.

FIG. 15 is a diagram showing a relationship between a valve opening phase difference between two intake valves and a cycle variation of an average flow velocity of intake air.

FIG. 16 is an explanatory diagram showing the effect of the embodiment of the present invention for each component in comparison with the conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Internal combustion engine main body 2 Cylinder 3 Cylinder head 4 Combustion chamber 5 Spark plug 6 Intake port 7 Intake manifold 8 Intake collector assembly 9 Intake pipe (branch) 10 Passage adapter 11 Air control valve 12 Air control valve mounting shaft 13 Air control valve Opening 14 first intake valve 15 second intake valve θ entrance angle of intake port α inclination angle of air control valve β angle of center of gravity of opening of air control valve

────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI F02F 1/42 F02F 1/42 F F02M 69/00 360 F02M 69/00 360C Joint panel Referee Chief Kenji Nishino Referee Judge Kiyota Eisai Yasuhiro Ujihara (56) References JP-A-63-266122 (JP, A) JP-A-5-231276 (JP, A) JP-A-5-202758 (JP, A) Jpn. ) Japanese Utility Model Showa 55-114355 (JP, U) Japanese Utility Model Hei 4-14736 (JP, U)

Claims (13)

(57) [Claims] 1. A spark ignition type internal combustion engine in which an air-fuel ratio is made lean according to operating conditions, an intake port having a shape for generating a vertical vortex in a cylinder , and an opening portion partially interposed in an intake passage. Sky formed
Comprising a gas control valve, and the air control valve during lean air-fuel ratio operation to a closed state,
Tumble ratio of the intake air flow in the Linda is 1.6 to 3.1, same
Air control so that the swirl ratio is 1.8 to 3.5.
A spark ignition type internal combustion engine, wherein a position of an opening of a control valve is set . 2. The intake passage is separated from an intake collector assembly.
Provided for each cylinder so that it branches to the intake port of each cylinder
The intake passage is made equal in length between the cylinders, and
The shape of the intake passage in a predetermined section immediately upstream of the valve is roughly
The spark ignition type internal combustion engine according to claim 1, wherein the internal combustion engine is the same. 3. A spark ignition type internal combustion engine according to claim 2, wherein said predetermined section has a linear shape. 4. The spark ignition type internal combustion engine according to claim 2, wherein the intake passage in the predetermined section is formed by a passage adapter separate from the other intake passages. 5. The intake passage according to claim 2, wherein a length of the intake passage in the predetermined section is set within a range of about 1.5 to 3.5 times an intake port inner diameter. A spark ignition type internal combustion engine according to any one of the preceding claims. 6. The air control valve according to claim 2, wherein an opening is formed at a position above the mounting shaft and offset in the radial direction. Spark ignition type internal combustion engine. 7. An opening of said air control valve, wherein an angle formed by a center line of a mounting axis of a line connecting a center of gravity of the air control valve and the center of the passage is set upward in a range of 45 to 75 degrees. The spark ignition type internal combustion engine according to claim 6, wherein 8. An opening of the air control valve, wherein an angle between the center of a line connecting the center of gravity of the air control valve and the center of the passage is set within an upper range of 60 to 70 degrees. The spark ignition type internal combustion engine according to claim 6. 9. The air intake valve according to claim 6, further comprising two intake valves driven with a phase difference so that the intake valve on the air control valve opening side opens earlier. A spark ignition type internal combustion engine according to any one of the preceding claims. 10. The spark ignition type internal combustion engine according to claim 2, wherein the air control valve is controlled so as to be inclined downward by a predetermined amount in a closed state. 11. A lean angle of the air control valve at the time of lean air-fuel ratio operation is set within a range of 20 to 30 degrees with respect to a cross section perpendicular to the central axis of the intake passage. The spark ignition type internal combustion engine according to claim 10, wherein 12. The spark ignition type internal combustion engine according to claim 2, wherein each of the intake ports is formed in a shape that generates a vertical vortex in a cylinder. 13. An intake port having a shape that generates a vertical vortex in a cylinder has a curved portion connected to a combustion chamber of the engine and a straight portion on an upstream side of the curved portion. 13. The spark ignition type internal combustion engine according to claim 12, wherein the angle is 50 mm or more, and an angle between a center line of the straight portion and a horizontal plane is within a range of 10 to 30 degrees.