JP2020165336A - Internal combustion engine - Google Patents

Abstract

To provide an internal combustion engine in which strong tumble flow can be created.SOLUTION: A center line of an intake port 4 is directed toward a lower portion of an exhaust port 5 at an upper portion of a cylinder bore 1. Accordingly, it can contribute to creation of tumble flow. A curtain ratio obtained by dividing an intake curtain area S by a minimum cross-sectional area E of the intake port 4 is over 2 when an intake valve 6 is lifted in maximum (preferably 3 or more). Intake air is continuously injected toward a lower region of the exhaust port 5 of the cylinder bore 1 without disturbed by a head portion 6b of the intake valve 6 since the curtain ratio is over 2 before the intake valve 6 reaches the maximum lift in an intake stroke. Accordingly, strong tumble flow can be created.SELECTED DRAWING: Figure 2

Description

The present invention relates to an internal combustion engine and is characterized by a tumble flow strengthening technique.

In a spark-ignition type internal combustion engine, if a tumble flow is applied to the intake air sucked into the cylinder bore, the mixture of fuel and air is enhanced, which can contribute to the improvement of output and the prevention of deterioration of the exhaust gas component. Therefore, many proposals have been made to generate a strong tumble flow.

For example, in Patent Document 1, a partition wall that divides the flow of intake air into upper and lower parts is provided in the intake port, and the intake air flowing above the partition wall is directed so as to flow upward as much as possible, thereby causing a tumble flow particularly in a low speed rotation range. We are trying to strengthen.

JP-A-2017-150379

In order to strengthen the tumble flow, it is important to direct the intake air flow toward the cylinder bore with as much directivity as possible without diffusing it. However, in the configuration of Patent Document 1, the intake port It is understood that it is not always sufficient as a measure for strengthening the tumble flow because it only gives a direction to a part of the intake air at the outlet part of.

On the other hand, regarding the area of the outlet portion of the intake port and the lift amount of the intake valve, the concept of the curtain area, which is the product of the outer peripheral length of the intake valve and the lift amount, is known, and the curtain area is the outlet portion of the intake port. The concept of the curtain ratio, which is the value divided by the area of, is also known. However, although the curtain ratio has a great influence on the inflow characteristics of the intake air, conventional research has not been conducted in relation to the generation of the tumble flow, and it has been considered mainly from the viewpoint of securing the intake air volume. I can say.

The present invention has been made in the wake of such a situation, and is intended to realize a configuration capable of strengthening the tumble flow by effectively utilizing the concept of the curtain ratio.

The internal combustion engine of the present invention is
"The intake port and the exhaust port have a cylinder head formed on the opposite side of the cylinder bore axis and an intake valve that opens and closes the outlet of the intake port, and the opening direction of the intake port is defined as described above. By directing the inner peripheral surface of the cylinder bore toward the lower part of the exhaust port, the intake air ejected from the intake port is guided by the cylinder bore to generate a tumble flow. "
It has a basic structure.

And in the above basic configuration
"The outer peripheral length of the outlet of the intake port is L, the lift amount of the intake valve is H, the intake curtain area of L × H is S, the minimum cross-sectional area of the intake port is E, and S / E is the curtain ratio. If so, the maximum curtain ratio when the lift amount is maximum is 2 or more, and there is a region where the curtain ratio increases to 2 or more in the intake stroke. "
The feature is added.

There are two ways to increase the curtain ratio: to make the minimum cross-sectional area of the intake port as small as possible and to make the maximum lift amount of the intake valve as large as possible, but both are practical because there are limits. It can be said that it is difficult to make the curtain ratio larger than 4. Therefore, it is estimated that the maximum curtain ratio is preferably about 3 to 4.

In order to continuously generate the tumble flow, it is preferable that the region where the curtain ratio increases to 2 or more in the intake stroke is as wide as possible. For example, it is preferable that the curtain ratio exceeds 2 in the time up to 2/3 of the time required for the intake valve to reach the maximum lift amount. In addition, since the maximum lift amount of the intake valve is limited, the curtain ratio is also limited, but if the curtain ratio is within 3, the intake valve is connected to the piston while ensuring the required intake amount. It can be said that there is no practical problem because the lift can be performed while avoiding interference.

By the way, it can be said that the magnitude of the curtain ratio and the tumble ratio have a positive correlation. That is, when the curtain ratio is increased, the degree to which the intake air is obstructed by the umbrella portion of the intake valve decreases, so that the straightness and directivity of the intake air are improved, and the function of generating the tumble flow is improved.

On the other hand, since the lift amount of the intake valve is limited, the minimum cross-sectional area of the intake port must be reduced in order to increase the curtain ratio, but if the minimum cross-sectional area of the intake port is reduced, the intake amount decreases. Therefore, in the past, attention was not paid to the curtain ratio with priority given to securing the intake amount, and as seen in Patent Document 1, the tumble ratio is improved by improving the shape of the intake port. It can be said that.

In other words, in the past, it is understood that the intake port should have an outlet area as large as possible, and the intake air was pushed into the cylinder bore to generate a tumble flow, but the effect of improving the strong tumble ratio is sufficient. It is understood that there was no such thing.

Although it is necessary to secure the intake amount, it is sufficient if the intake amount can be secured in the entire intake stroke, and it is understood that it is not always necessary to push the intake into the cylinder bore from the beginning of the intake stroke. Rather, it is understood that if the intake air is sent to the cylinder bore in a small amount in the intake stroke to generate a strong tumble flow, the mixture of fuel and air (or the mixture of the air-fuel mixture and EGR gas) is also improved.

The present invention has been made based on such findings and analysis, and the maximum curtain ratio is 2 or more, and the curtain ratio exceeds 2 before the intake valve reaches the maximum lift amount. Therefore, at the earliest possible stage of the intake stroke, the intake air can be ejected to the cylinder bore with strong directionality (direction) without being disturbed by the umbrella part of the intake valve, thereby causing the tumble flow. (Ie, the tumble ratio can be improved).

Since the maximum lift amount of the intake valve has a limit due to the problem of interference with the piston and the restriction of the cam profile, it is necessary to reduce the minimum cross-sectional area of the intake port in order to increase the curtain ratio. As described above, since the intake amount may be secured in the entire intake stroke, the required output can be secured even if the minimum cross-sectional area of the intake port is reduced.

Rather, it can be said that the strengthening of the tumble flow is promoted by the continuous inflow of the highly directional intake flow into the cylinder bore over a wide range of the intake stroke. That is, when the curtain ratio is small, the intake air is forcibly pushed in at the initial stage of the intake stroke and the intake air tends to diffuse in the cylinder bore. However, in the present invention, the directional intake air flow is continuously applied to the cylinder bore. Since it flows in, it can be said that a tumble flow can be generated until the piston reaches bottom dead center and the intake stroke is completed.

As described above, when the curtain ratio reaches 2 in the time up to 2/3 of the time when the intake valve reaches the maximum lift amount, it is suitable for maintaining the intake flow and generating the tumble flow, and the intake amount. It was also suitable in terms of securing. The same was true when the region where the curtain ratio exceeded 2 existed in the range of 30 to 90 degrees in the crank angle.

(A) is a vertical sectional front view of the embodiment, and (B) is a partially enlarged view of a main part. (A) is a vertical sectional front view of the intake stroke, and (B) is a partially enlarged view of the main part. It is a longitudinal front view at the end of the intake stroke. It is a figure which shows the effect, etc., (A) is a planar schematic diagram for showing a measurement position, (B) is a graph which shows the relationship (curtain ratio) between the intake port outlet area and the intake valve lift amount, (C) ) Is a graph showing the relationship between the lift amount and the tumble ratio. It is a graph which shows the lift curve which is the relationship between the lift amount of an intake valve and a crank angle.

Next, an embodiment of the present invention will be described with reference to the drawings. This embodiment is applied to an internal combustion engine for automobiles.

(1). Basic structure The basic structure of an internal combustion engine is the same as the conventional one, and includes a cylinder block 2 formed by arranging a plurality of cylinder bores 1 in the direction of the crank axis and a cylinder head 3 fixed to the upper surface thereof. In the cylinder head 3, a pair of intake ports 4 and exhaust ports 5 arranged in the direction of the crank axis are formed on both sides of the cylinder bore axis.

The outlet 4a of the intake port 4 is opened and closed by the intake valve 6, and the inlet 5a of the exhaust port 5 is opened and closed by the exhaust valve 7. Needless to say, the intake valve 6 and the exhaust valve 7 are provided with valve stems 6a and 7a and umbrella portions 6b and 7b, and are urged in the closing direction by a spring (not shown) and a cam (not shown). Pushed down by.

A mountain-shaped (pent roof type) combustion chamber 8 is formed in the cylinder head 3 in a state concentric with each cylinder bore 1, and the intake valve 6 and the exhaust valve 7 are in a state orthogonal to the inclined surface of the combustion chamber 8. Have been placed. Further, the intake valve seat 9 is press-fitted into the outlet 4a of the intake port 4, and the exhaust valve seat 10 is press-fitted into the inlet 5a of the exhaust port 5.

A spark plug 11 is attached to the central portion of each combustion chamber 8 of the cylinder head 3. On the other hand, the piston 12 is slidably fitted in the cylinder bore 1. Although not shown, the tip of a fuel injection injector (not shown) faces the inlet side of the intake port 4.

The intake port 4 has a linear posture, and its center line 13 reaches the upper part of the cylinder bore 1 and the lower part of the exhaust valve 7. Therefore, the intake air is ejected toward the lower portion of the exhaust valve 7 in the cylinder bore 1. As a result, as shown in FIG. 3, a tumble flow 14 is generated in the intake stroke.

In the present embodiment, the cross-sectional area of the intake port 4 is gradually reduced from the inlet to the outlet, but the intake port 4 has a recess 15 for letting the stem 6a of the intake valve 6 escape. , The minimum cross-sectional area E is set at the portion corresponding to the recess 15.

(2). Tumble flow strengthening means In the present embodiment, the outer diameter of the intake valve 6 is D, the lift amount of the intake valve 6 is H, the intake curtain area of L × H is S, and the minimum cross-sectional area of the intake port 4 is set. As described above, when E and S / E are set to the curtain ratio, the maximum curtain ratio when the lift amount H is maximum is set to 2 or more, and therefore, the region where the curtain ratio increases to 2 or more in the intake stroke. Exists.

As specific examples, the outer diameter D of the intake valve 6 is 14 mm, the outer peripheral length L of the intake valve 6 is about 44 mm, the minimum cross-sectional area E of the intake port 4 is 98 mm2, the inner diameter of the intake valve 6 is about 10.2 mm, and the intake valve. The maximum lift amount of 6 is set to 8 mm. Therefore, as shown in FIG. 4B, the maximum curtain ratio is about 3.6.

The intake valve 6 opens in a lift curve shown in FIG. 5, but since the curtain ratio is about 3.6 at the maximum lift amount, the lift amount of the intake valve 6 slightly exceeds 4 mm in the intake stroke. At the stage, the curtain ratio has reached about 2.

By the way, how much of the intake flow contributes to the generation of the tumble flow 14 is analyzed in relation to the lift amount of the intake valve 6. As a premise, as shown in FIG. 4, the inner circumference of the intake valve 6 (or the inner circumference of the intake port outlet 4a) is plotted by 30 degrees, and 12 measurement points P1 to P12 are set. P1 is a portion closest to the adjacent intake valve seats 9, and is continuous with P2, P3 ... In the clockwise direction.

Therefore, when viewed from the intake flow direction, P3 to P5 are located in front of the valve stem 6a, P9 to P11 are located in front of the valve stem 6a, and P12 to P2 and P6 to P8 are in the flow direction. It is located on the side of. From this, the intake air flowing through the points P3 to P5 becomes a flow that inhibits the tumble flow, while the intake air flowing through P9 to P11 greatly contributes to the generation of the tumble flow and flows through the parts P12 to P2 and P6 to P8. Intake can be said to be neutral (neither contributes nor impede) to the generation of tumble streams.

Then, the graph of FIG. 4C shows how the flow at each point is related to the generation of the tumble flow in relation to the lift amount of the intake valve 6. In FIG. 4C, the total amount of intake air at each point is 100, but as the lift amount increases, the flow rates of P9 to P11, which greatly contribute to the generation of the tumble flow, increase. It can be seen that the flow rate in other parts is decreasing. From this, it can be understood that the tumble flow is continuously generated in the present embodiment.

It should be noted that, first, the flow rate increase curve of P9 to P11 is steep until the lift amount reaches about 3 mm, but when the lift amount exceeds 3 mm, the slope becomes gentle and the lift is lifted. There is a threshold in the relationship of flow rate increase with respect to quantity.

Moreover, since the maximum value of the curtain ratio is about 3.6, it can be said that the curtain ratio is about 2 (about 1.9) when the lift amount is 4 mm, but when viewed in reverse, It can be said that if the curtain ratio is set to be about 2 when the lift amount is 4 mm, continuous generation of the tumble flow can be realized and a strong tumble flow can be generated.

As described above, the threshold value appears when the lift amount is 3 mm, but considering the analysis error, when the maximum lift amount of the intake valve 6 is 8 mm, the curtain ratio is 1 when the lift amount is 3 to 4 mm. It can be said that the minimum cross-sectional area E of the intake port and the outer diameter D of the intake valve 6 should be set so as to be about 0.8 to 2.0.

Further, looking at the relationship between the time it takes for the intake valve 6 to reach the maximum lift amount and the curtain ratio, in the embodiment, the maximum curtain ratio is about 3.6, so that the lift amount increases linearly in relation to the time. Then, in the process, the curtain ratio reaches about 2 when the lift amount is about 4.5 mm, but from the viewpoint of the continuous tumble flow generation effect, the curtain takes about 2/3 of the time to reach the maximum lift amount. It is presumed that the ratio should be set to reach 1.8 to 2.

Looking at the relationship between the curtain ratio and the crank angle, the opening angle of the intake valve 6 is about 180 degrees, but it is preferable that a region where the curtain ratio exceeds about 2 exists at 30 to 90 degrees. ..

Although the embodiments of the present invention have been described above, the present invention can be embodied in various ways without departing from the spirit of the present invention. From the viewpoint of securing the intake amount, it can be said that there is a limit to the reduction in the diameter of the intake valve, so it may be a good idea to increase the lift amount of the intake valve. Further, it is preferable that the stem of the intake valve has a diameter as small as possible.

The invention of the present application can be embodied in an internal combustion engine. Therefore, it can be used industrially.

1 Cylinder bore 2 Cylinder block 3 Cylinder head 4 Intake port 4a Intake port outlet 5 Exhaust port 6 Intake valve 8 Combustion chamber 9 Intake valve seat E Minimum cross-sectional area of intake port H Intake valve lift amount S Intake curtain area

Claims (1)

It has a cylinder head formed on opposite sides of the cylinder bore axis of the intake port and the exhaust port, and an intake valve that opens and closes the outlet of the intake port, and the opening direction of the intake port is the cylinder bore. The intake air ejected from the intake port is guided by the cylinder bore to generate a tumble flow by directing it toward the lower part of the exhaust port on the inner peripheral surface of the above.
When the outer peripheral length of the intake valve is L, the lift amount of the intake valve is H, the intake curtain area where L × H is S, the minimum cross-sectional area of the intake port is E, and S / E is the curtain ratio. The maximum curtain ratio when the lift amount is maximum is 2 or more, and there is a region where the curtain ratio increases to 2 or more in the intake stroke.
Internal combustion engine.

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