KR100303976B1 - Gasoline Engine Combustion Chamber - Google Patents

Abstract

The present invention relates to a combustion chamber of a gasoline engine, and has an object to form a bowl having a predetermined shape on the upper surface of the piston forming the lowermost portion of the combustion chamber, and to allow the mixer to flow smoothly inside the bowl. According to the present invention, when the flow of the mixer is rotated counterclockwise in the cylinder with respect to the intake side, the uppermost surface of the piston is formed to protrude above the cylinder block at compression top dead center, and concave to the upper surface of the protruding piston. The piston bowl is formed, and the bowl has an egg-shaped asymmetric oval shape when the piston is lowered down along the cylinder bore side, and the front, rear, left, and right sides of the piston are in the direction of the exhaust valve side of the engine and the intake of the engine, respectively. The center line of the combustion chamber and the exhaust valve side direction (front), in which the long axis of the ellipse passes from the rear direction of the engine (left) to the front direction of the engine (right) in the valve side direction, the rear direction of the engine, and the front direction of the engine. It is formed between the center line of the combustion chamber and the intake valve side direction (rear), and an asymmetric ellipse is formed between the center line of the combustion chamber and the exhaust valve. The radius of curvature of the elliptical arc is the curvature radius of the elliptical arc that extends from the intake valve side direction (rear to bottom) to the front direction of the engine (right) when it is divided by the center line of the combustion chamber passing between the valves. It is larger than the radius of curvature of the elliptical arc leading to the rear direction (left) of the engine.

Description

Combustion chamber of gasoline engine

The present invention relates to a combustion chamber of a gasoline engine, wherein a bowl having a predetermined shape and depth is formed on an upper surface of a piston forming a lower portion of the combustion chamber, and the mixer is configured to smoothly flow in the bowl to further improve engine performance. The combustion chamber of a gasoline engine that can be made.

In general, automotive internal combustion engines require the combustion of the mixer completely in the cylinders that make up the engine to increase efficiency and reduce emissions.

To this end, in order to realize fuel saving, air pollution reduction, and output improvement, a mixer inside the cylinder at the ignition timing is formed close to the theoretical air-fuel ratio around the spark plug, and extremely thin in the rest, so that combustion is performed even at a thin air-fuel ratio. A layered lean-burn internal combustion engine is being applied to automobiles.

In order to realize such laminar lean combustion, a swirl control valve is installed on an intake passage of an engine having two or more intake ports for each cylinder in a conventional internal combustion engine, so that the degree of layer mixing of the in-cylinder mixer and swirl It is proposed to adjust the degree. GDI (gasoline direct injection) engine ex.us 5,553,588 (Toyoda), SAE 980149 (Nissan), us 5,305,720 (Mitsubishi).

In order to combust the ultra-thin mixer, a stratification technique for enriching fuel only in a predetermined region (gap of spark plug) inside the combustion chamber is required. The related art will be described below.

1 is a side cross-sectional view showing a conventional gasoline engine (Toyota, us 5,553, 588) and FIG. 2 is a plan view showing the flow of a mixer inside a piston bowl of a conventional gasoline engine.

First, as shown in FIG. 1, in the prior art, a swirl air flow is formed on the intake port 12 side to flow into the cylinder 10 through the intake valve 14, and then the end of the compression of the piston 16 The swirl flow into the bowl 18 of the piston 16 and injects fuel into the injector 20 whereby the fuel rides along the swirl air flow and reaches around the spark plug 22 to make the mixer rich. It is configured to be stratified. At this time, the bowl 18 formed at the top of the piston 16 has a flat bottom surface and is concave so as to form a predetermined flow so that the injected fuel is not unnecessarily diffused. Shows exhaust port and exhaust valve.

As shown in FIGS. 1 and 2, the flow of the mixer is injected into the area 5a of the injector 20 mounted on the combustion chamber slide of the cylinder 10. It flows along the 5b line by the swirling strongly rotating swirl flow.

At this time, the fuel flows along the 5b line, which is a straight section, and is mixed with the air, thereby advantageously igniting.

Ignition occurs when a rich portion of the fuel passes through the spark plug 22, and a bowl-shaped 5f section is provided in the bowl 18 to prevent unnecessarily spreading the mixer that has already passed before the ignition. The ignited flame is configured to propagate along section 5c.

In addition, the bowl 18 is formed relatively deep so that the fuel injected from the injector 20 can collide with the bottom surface of the bowl 18 to a minimum, and the spark flow piggybacks the fuel injected strongly at high pressure to spark plugs. The bowl 18 is formed in a predetermined shape so as to be directed toward the (22) side. Line 5b, which leads the flow carrying the mixer to the spark plug 22 side, is close to the spark plug 22. The engines on the SAE 980149 and us 5,305,720 are reverse tumble engines.

In the prior art configured as described above, since the flow generated on the intake pipe side does not naturally flow into the bowl of the piston at the end of the compression, it is difficult to achieve the stratification of the mixer due to the loss of flow resulting in turbulent flow.

In addition, when the bowl wall of the piston and the spark plug are separated from each other in order to increase the bowl, the stratified mixer may spread before the ignition is ignited. If the stratified mixer diffuses before ignition, the combustion may be incomplete and result in a decrease in power.

In addition, the separation distance between the bowl bottom of the piston and the spark plug is so great that it is difficult for the stratified fuel to rise towards the spark plug, thereby limiting the need to use a spark plug with a long electrode.

The present invention has been made to solve the above problems, and an object thereof is to provide a combustion chamber of a gasoline engine that can improve the performance of the engine.

1 is a side cross-sectional view showing a conventional gasoline engine.

2 is a plan view showing the flow of the mixer inside the piston bowl of a conventional gasoline engine.

3 is a perspective view showing a bowl shape according to an embodiment of the present invention.

4 is a plan view of FIG.

5 is a cross-sectional view taken along the line A-A of FIG.

FIG. 6 is a side cross-sectional view showing a fuel injection state for gathering side cross-section B-B of FIG.

7 to 9 are views showing the flow of the mixer according to the position of the piston according to an embodiment of the present invention, a perspective view showing the initial compression / compression / final compression of the piston, respectively.

10 to 13 show the flow of the mixer according to an embodiment of the present invention, the initial state of the fuel injection of the injector / the state in which the mixer is moved along the side wall in the front direction / the state in which the mixer is close to the spark plug A top view showing the mixer / mixer visible inside the bowl.

14 to 16 show the flow of the mixer according to another embodiment of the present invention, respectively, in which the mixer is moved along the front side wall / the mixer is in close proximity to the spark plug. Top view showing the state of assembling.

* Explanation of symbols for main parts of the drawings

100: piston

100a: exhaust valve side direction (thrust direction)

100b: Intake valve side direction (Anti-Thrust direction)

100c: rear direction 100d: front direction

110: bowl 200: cylinder

210: intake valve 220: exhaust valve

230: intake port 240: exhaust port

In order to achieve the above object, the present invention is to form a bowl having a predetermined shape and depth on the upper surface of the piston forming the lowermost part of the combustion chamber, characterized in that to allow the mixer to flow smoothly inside the bowl, In a layered lean-burn gasoline direct injection engine that stratifies a mixer in a combustion chamber by using the air flow on the side and the shape of a piston upper side, the performance of the engine is increased. When rotating in a counterclockwise direction at the top, the top surface of the piston is formed at the compression top dead center projecting over the cylinder block, the protruding piston upper surface is formed a concave piston bowl, the bowl is the piston Shape of the piston bowl when the cylinder is lowered along the cylinder bore side is The long axis of the ellipse is asymmetrical oval in shape, and the front, rear, left, and right sides of the piston are in the exhaust valve side direction of the engine, the intake valve side direction of the engine, the rear direction of the engine, and the front direction of the engine, respectively. And is formed between the center line of the combustion chamber and the intake valve side direction (before) between the center line of the combustion chamber and the exhaust valve side direction (before) passing from (left) to the front direction (right) of the engine. When divided into four elliptical arcs divided by the center line of the combustion chamber and between the exhaust valve and the intake valve, the radius of curvature of the elliptical arc is the front direction of the engine in the intake valve side direction (rear = bottom). The radius of curvature of the elliptical arc leading to (right) is the radius of curvature of the elliptical arc extending from the exhaust valve side direction (before) to the rear direction of the engine (left). It will largely formed.

In the above configuration, the shape of the bottom surface of the bowl is inclined along the long axis of the asymmetric ellipse representing the bowl shape, and the intake valve is disposed between the exhaust valve side direction (front = top) and the rear direction of the engine (left). It is located higher than between the lateral direction (back = bottom) and the front direction (right) of the engine, and the bottom surface of the bowl is formed flat.

On the other hand, the height of the side wall of the bowl in the rear direction (left) formed in the intake valve side direction (before) in the exhaust valve side direction (before) of the side wall of the bowl which is in contact with the mixer flowing into the bowl is It is formed lower than the side wall height of the bowl in the front direction (right) formed in the exhaust valve side direction (before) in the intake valve side direction (after).

And the intake valve side direction (rear) in the spark plug direction located in the combustion chamber center, the exhaust valve side direction (before) in the spark plug direction, and the rear direction (left) of the engine in the spark plug direction. An inclined surface is formed among the protruding portions of the piston uppermost surface between the intake valve side directions (rear).

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a perspective view showing a bowl shape according to an embodiment of the present invention, FIG. 4 is a plan view of FIG. 3, FIG. 5 is a cross-sectional view taken along line AA of FIG. 4, and FIG. It is a side cross-sectional view which shows the fuel injection state for the purpose of showing. Hereinafter, a case in which the mixer of the combustion chamber rotates counterclockwise will be described.

First, as shown in FIGS. 3 to 6, the present invention uses the air flow on the intake side and the top of the piston 100 to stratify the mixer in the cylinder 200 to improve the performance of the engine. In the upper side of the cylinder 200, intake and exhaust ports 210 and 220, intake and exhaust valves 230 and 240, spark plugs 250, and injectors 260 are provided, and a piston is provided below the cylinder 200. 100 is positioned to form a combustion chamber.

As a feature of the present invention, a bowl 110 having a predetermined shape is formed at a position forming the upper side surface of the piston 100. Hereinafter, looking at the shape of the bowl 110 in detail, the bowl 110 is the shape of the perston bowl 110 when the piston 100 is lowered down along the cylinder bore side is an asymmetric oval of an oval shape. In the state where the front, rear, left and right sides of the piston 100 are respectively set as the exhaust valve side direction 100a of the engine, the intake valve side direction 100b of the engine, the rear direction 100c of the engine, and the front direction 100d of the engine, Between the center line of the combustion chamber where the long axis of the ellipse passes from the rear direction of the engine (left, 100c) to the front direction of the engine (right, 100d) and the direction of the combustion chamber (front, 100a) and the intake valve side direction (rear) , The radius of curvature of the elliptical arc is in the intake valve side direction (after = lower) when the asymmetric ellipse is divided into four elliptical arcs by dividing the asymmetric ellipse into the center line of the combustion chamber and between the exhaust valve and the intake valve. Front of the engine, from 100b) This effort is (R, 100d) elliptical arc radius of curvature leading to the formed larger than the elliptical arc radius of curvature leading to the rear direction (left, 100c) of the engine at the exhaust valve-side direction (front, 100a).

On the other hand, the shape of the bottom surface of the bowl 110 is inclined along the long axis of the asymmetric ellipse representing the shape of the bowl 110, the exhaust valve side direction (front = top, 100a) and the rear direction of the engine (left, 100c) Is located higher than between the intake valve side direction (back = lower, 100b) and the front direction of the engine (right, 100d), and the bottom surface of the bowl 110 is formed flat.

And, the rear side direction (left, 100c) formed in the intake valve side direction (after, 100b) in the exhaust valve side direction (before, 100a) of the side wall of the bowl 110 is in contact with the flow of the mixer introduced into the bowl (110) The side wall height Hc of the bowl 110 is lower than the side wall height Ha of the bowl in the front direction (right, 100d) formed in the intake valve side direction (after, 100b) in the exhaust valve side direction (before, 100a). Is formed.

In addition, among the portions protruding from the upper surface of the piston 100, three portions forming the inclined surface (X, Y, Z: see also FIG. 3) are formed, and each of the three spark plugs 250 are located at the center of the combustion chamber. Direction intake valve side direction (rear, 100b), the spark plug 250 in the exhaust valve side direction (front, 100a), the spark plug 250 in the rear direction of the engine (left, 100c) wave intake valve An inclined surface is formed among the protruding portions of the uppermost surface of the piston 100 between the lateral directions (after, 100b).

Referring to the operation of the combustion chamber of the gasoline engine according to an embodiment of the present invention configured as described above are as follows.

7 to 9 are views showing the flow of the mixer according to the position of the piston according to an embodiment of the present invention, a perspective view showing the initial compression / compression / final compression of the piston, respectively. As shown in FIGS. 7 to 9, the flow flowing from the intake side, which is designed to generate swirl flow, is rotated while inclined to the horizontal plane of the cylinder 200 during the intake process. As shown in FIG.

As the piston 100 rises, both side walls of the bowl 110 of the piston 100 protruding on the top surface of the piston 100 may introduce rotating swirl flow into the bowl 110 of the perston 100. And at the same time it serves as a guide so that the flow introduced can continue to rotate inside the bowl 110 of the piston 100 (shown in FIGS. 8 and 9).

On the other hand, when comparing the side wall height Hc of the circular arc c and the side wall height Ha of the circular arc a shown in FIGS. 3 and 4, since the circular arc c is low and the circular arc a is formed relatively high, the piston Minimizing the flow of rotation in the cylinder 200 to block the flow of rotation horizontally on the circular arc c side wall when the 100 is elevated, which results in the inflow of flow into the bowl 110 rather than having both sides having the same height. Make it more natural.

In addition, the bottom surface of the bowl 110 is inclined in consideration of the inclination angle of the inclined swirl generated in the intake port 230 when the flow flowing in the bowl 110 of the piston 100, the bottom surface The inclined swirl flow introduced into the bowl 110 is minimized by minimizing friction with the combiner, and the inside of the bowl 110 is maintained inside the bowl 110, and still exists as a strong swirl flow inside the bowl 110.

As shown in FIG. 9, when the piston is gradually closer to the combustion chamber, fuel is injected into the bowl 110 of the piston 100 by the injector 260 installed at the lower end of the intake port 230. (Shown in Figure 10)

In this case, as shown in FIGS. 4 and 6, a portion of the injected fuel collides with the bottom of the bowl 110 and bounces up, and the remaining fuel is piggybacked in a strong swirl inside the bowl 110 and mixed with air. While moving toward the spark plug 250 side along the side wall of the bowl 110 of the piston 100 of the arc b line (shown in FIGS. 11 and 12). The fuel bounced off the bottom of the bowl 110 is also filled in the bowl 110 and gradually rides on the rotating swirl flow.

As a result of the swirl flow, when the stratified mixer passes through the spark plug 250 (shown in FIG. 12), the spark plug 250 is ignited and the nuclei of flame are generated in the partially thickened stratified mixer. The flame generated is still transferred to the entire bowl 110 of the piston 100 along the sidewalls of the bowl 110 of the piston 100 of arc line C, under the influence of the rotating flow inside the bowl 110 of the piston 100. It spreads in an instant.

Therefore, even if a very small amount of fuel is injected from the injector 260, if the mixer is partially stratified in the vicinity of the spark plug 250, stable combustion is possible inside the cylinder 200.

Since the ignition timing of the engine depends on the rotational speed and the load of the engine, sometimes the ignition occurs after passing near the stratified spark plug 250.

In such a case, it is necessary to prevent diffusion of the stratified mixture temporarily. In the present invention, in the shape of the bowl 110 of the piston 100, the region after passing the spark plug 250 is designed to be narrow, thereby temporarily mixing the mixer. By confinement, it is possible to prevent rapid diffusion of the mixer and to ignite it (shown in FIG. 13).

On the other hand, Figures 14 to 16 show the flow of the mixer according to another embodiment of the present invention, respectively, the state in which the mixer is moved along the side wall in the front direction / the mixer is in close proximity to the spark plug / bowl It is the top view which shows the state gathering inside. As shown in FIGS. 16 to 18, when the piston is gradually approached the combustion chamber, fuel is injected into the bowl 110 of the piston 100 by the injector 260 installed at the lower end of the intake port 230. (Shown in Figure 16).

At this time, a portion of the injected fuel is bounced up by colliding with the bottom of the bowl 110, the remaining fuel is mixed with air mixed with air swirled in a strong swirl inside the bowl 110 (b) of the piston 100 of the circular arc b line ( 110) it is moved along the side wall toward the spark plug 250 (shown in FIGS. 16 and 17). The fuel bounced off the bottom of the bowl 110 is also filled in the bowl 110 and gradually rides on the rotating swirl flow.

At the moment when the stratified mixer, which is piggybacked in swirl flow, passes through the spark plug 250 (shown in FIG. 17), the spark plug 250 is ignited and the nuclei of flame are generated in the partially thickened stratified mixer. The flame generated is still instantaneously through the bowl 110 of the piston 100 along the sidewalls of the bowl 110 of the piston 100 of arc c line under the influence of the rotating flow inside the bowl 110 of the piston 100. Spreads on

Therefore, even if a very small amount of fuel is injected from the injector 260, if the mixer is partially stratified in the vicinity of the spark plug 250, stable combustion is possible inside the cylinder 200.

Since the ignition timing of the engine depends on the rotational speed and the load of the engine, sometimes the ignition occurs after passing near the stratified spark plug 250.

In such a case, it is necessary to prevent diffusion of the stratified mixture temporarily. In the present invention, in the shape of the bowl 110 of the piston 100, the region after passing the spark plug 250 is designed to be narrow, thereby temporarily mixing the mixer. Confined to prevents rapid diffusion of the mixer and then ignites (shown in FIG. 18).

On the other hand, the present invention is not limited to the above-described embodiment can be carried out in various modifications within the scope allowed by the technical idea of the present invention.

For example, in the present invention, the bottom surface of the bowl is described as an example, but by flattening the inclined surface of the bowl, it is possible to eliminate the friction that can be caused by a simple swirl flow hit the inclined bottom surface. In addition, the angle of the inclined surface in contact with the arc c line can be made the same as the angle of the inclined surface in contact with the arc a line by making the angle of the inclined plane on the intake pipe side of the piston top surface constant. You can also strengthen.

According to the present invention as described above has the following effects.

First, when the suction flow generated in the intake pipe is introduced into the bowl of the piston, the inflow loss is small due to the smooth curve.

Second, it is easy to preserve the swirl flow by minimizing friction with the bottom of the bowl while the flow flowing into the piston bowl is compressed. Therefore, stable combustion in the ultra-lean state, which is an important technology of the gasoline direct injection engine, is prevented. Stratification of the mixer is very easy.

Third, since the shape of the piston is an egg-shaped asymmetrical oval composed of one circular arc, there is almost no flow loss resulting from the rapid change of shape, and the upper part of the upper left side of the ellipse is relatively narrower than the lower part, so that the mixer flowing inside the bowl is the upper part. Gathered in the can prevent the diffusion, thereby igniting can be easily performed.

Fourth, since the lower portion is formed relatively wide and low in the shape of the piston bowl, the generated flame is easy to propagate throughout the cylinder, thereby improving the output performance.

Claims (4)

In a layered lean-burn gasoline direct injection engine that stratifies a mixer in a combustion chamber by using an air flow on the intake side and a shape of an upper portion of the piston 100, the engine of the mixer is based on the intake side. When the flow rotates counterclockwise in the cylinder 200, the uppermost surface of the piston 100 is formed to protrude above the cylinder block during compression top dead center, the protrusion is concave in the upper surface of the piston 100 The piston bowl 110 is formed to be formed, the bowl 110 is the shape of the piston bowl 110 when the piston 100 is lowered down along the cylinder bore side of the egg-shaped asymmetric oval, The front, rear, left and right sides of the piston 100 are in the exhaust valve side direction 100a of the engine, the intake valve side direction 100b of the engine, the rear direction 100c of the engine, and the front direction 100d of the engine, respectively. The center line and the intake of the combustion chamber between the center line of the combustion chamber where the long axis of the ellipse extends from the rear direction of the engine (left, 100c) to the front direction of the engine (right, 100d) and the exhaust valve side direction (before, 100a). The elliptical arc is formed toward the valve side (100b) and is divided into four elliptical arcs by dividing the asymmetric ellipse into a centerline of the combustion chamber passing between the combustion chamber center line and the exhaust valve and the intake valve. The radius of curvature of the elliptical arc that extends from the intake valve side direction (rear = lower, 100b) to the front direction of the engine (right, 100d) is the rearward direction of the engine in the exhaust valve side direction (front, 100a). Left, the combustion chamber of the gasoline engine, characterized in that formed larger than the radius of curvature of the elliptical arc leading to 100c). The shape of the bottom surface of the bowl 110 is inclined along the long axis of the asymmetric ellipse representing the shape of the bowl 110, the exhaust valve side direction (front = top, 100a) and the engine The rear direction (left, 100c) is located higher than the intake valve side direction (rear = lower, 100b) and the front direction of the engine (right, 100d), the bottom surface of the bowl 110 is flat The combustion chamber of the gasoline engine characterized by the above-mentioned. The intake valve side direction (3) according to claim 1 or 2, wherein the mixer introduced into the bowl (110) flows in the exhaust valve side direction (before, 100a) of the side walls of the bowl (110) which are in contact with each other. Afterwards, the side wall height Hc of the bowl 110 in the rear direction (left, 100c) formed in 100b) is the front direction formed in the exhaust valve side direction (before, 100a) in the intake valve side direction (after, 100b). A combustion chamber of a gasoline engine, characterized in that it is formed lower than the side wall height Ha of the bowl of (right, 100d). According to claim 3, In the direction of the ignition plug 250 located in the center of the combustion chamber in the intake valve side direction (after, 100b), From the ignition plug 250 in the direction of the exhaust valve side (pre, 100a), Gasoline engine, characterized in that the inclined surface formed in the protruding portion of the uppermost surface of the piston 100 in the direction of the spark plug 250 between the rear direction (left, 100c) and the intake valve side direction (after, 100b) of the engine Combustion chamber.