JP5537110B2 - Internal combustion engine - Google Patents

Description

  The present invention relates to an internal combustion engine, and more particularly to a spark ignition internal combustion engine such as a gasoline engine.

In a spark ignition type internal combustion engine, the mixing property of air and fuel is improved by applying a swirl flow to the air-fuel mixture in the combustion chamber, and many proposals have been made. This swirl flow includes swirl flow swirling around the axis of the piston and cylinder bore, and tumble flow swirling around a virtual line perpendicular to the axis of the piston and cylinder bore (longitudinal vortex). As a means to do this , a guide recess is formed in the crown surface (top surface) of the piston.

Examples thereof are described in Patent Documents 1 to 4, for example. Among Patent Documents 1 to 3, concave plants, has become asymmetrical curved surface so close curvature radius in the area on the outlet radius of curvature in the area closer to the suction port becomes larger small and patents In Document 1, an inclined squish surface is provided at the periphery of the crown surface of the piston. On the other hand, in Patent Document 4, the recess has a symmetrical shape, and a squish surface having an equal depth and an equal width is provided in an annular shape on the periphery of the crown surface.

Now, the air-fuel mixture jetted straight from the intake port changes its flow toward the piston crown surface after colliding with the cylinder bore, and further flows toward the cylinder head roof surface. what it is, which forms a tumble flow by causing sustained flow of fuel mixture, so that the direction change of the mixture is smooth, as in the patent documents, forming a recess on the crown surface of the piston And guides the flow of the air-fuel mixture. Further, the roof surface of the cylinder head is inclined with respect to the axis of the cylinder bore so that the air-fuel mixture is also guided by the roof surface of the cylinder head.

JP 2001-98947 A Japanese Patent Laid-Open No. 02-215922 Japanese Patent Laid-Open No. 11-036977 JP 10-339219 A

As already mentioned, the gas mixture ejected from the air inlet rapidly direction changes collides with the cylinder bore, and so while the flow rate decreases the guided with concave plant towards the cylinder head, as in Patent Documents 1 to 3 It can be said that it is reasonable to guide the flow of the air-fuel mixture smoothly so that the concave profile is formed so that the radius of curvature becomes small at a location close to the exhaust port.

Now, the air-fuel mixture to which the tumble flow is applied is compressed by the piston and eventually ignited, but it is preferable that the air-fuel mixture keeps the tumble flow until the piston reaches the ignition timing. However, it is hard to say that each patent document has been sufficiently studied in this regard. Although it is conventional to form a squish surface on the piston for knock prevention, conventionally, the relationship is also fully discussed in the knocking prevention squish surface and tumble generating concave plants It's hard to say.

The present invention has been made in view of such situation, the point of forming a concave plants piston asymmetrically so that the radius of curvature of the portion close to the exhaust port becomes smaller while following Patent Documents 1 to 3, An object of the present invention is to provide a further improved internal combustion engine.

  An internal combustion engine according to a first aspect of the present invention includes a piston that is reciprocally disposed in a cylinder bore, and a cylinder head that closes the cylinder bore, and the cylinder head is inclined with respect to an axis of the cylinder bore. A combustion chamber having a substantially trapezoidal cross section having a roof surface formed is formed, and an intake port that is opened and closed by an intake valve and an exhaust port that is opened and closed by an exhaust valve are axially centered on the inclined roof surface of the combustion chamber. And an ignition plug is disposed at a substantially central portion of the combustion chamber, while being orthogonal to the direction in which the exhaust port and the intake port are aligned and of the piston. A main recess is formed on the crown surface of the piston for imparting a swirling flow to the air-fuel mixture ejected from the intake port when viewed from the direction orthogonal to the axis when viewed from the front.

Wherein the inner peripheral edge of the crown surface of the piston squish surface inclined relative to the axis is formed in an annular shape, the inside of the front Symbol squish surface, formed as the main recess is surrounded by the squish surface The main recess is configured to expand along the squish surface from the side close to the exhaust port toward the side close to the intake port, and the main recess is the side close to the exhaust port. a first area located in a second area located closer to the intake port, and consists of three areas of the third area located between these first area and a second area, wherein the inner surface of each area is curved in a longitudinal sectional front view, these are the radius of curvature of the inner surface of each area, the longitudinal front view, the curvature of the first area radius is rather smaller than the curvature radius of the second area, third the radius of curvature of the area Serial has become relationship is several times the curvature radius of the second area further includes the deepest boundary between the first area and the third area, the first area and the third area, and the second area And the third area are smoothly continuous.

The center of curvature of the third area is closer to the exhaust port than the axial center of the piston. And each said area is curving so that it may become concave toward a cylinder head also in the vertical side view orthogonal to the vertical front view.

The invention of claim 2 is a preferred embodiment of claim 1, and in this invention, the dimension of the squish surface measured in the axial direction of the piston and the depth dimension of the deepest part of the main recess are roughly shown. Set the same.
The invention of claim 3 is the invention according to claim 1 or 2, wherein two exhaust ports are arranged side by side in the axial direction of the crankshaft and are opened and closed by an exhaust valve, respectively, Two sub-recesses corresponding to the exhaust valve are formed at a position close to the exhaust port in a state of being located inside the squish surface. These two sub-recesses, the squish surface, and the main The area surrounded by the recess is a flat surface perpendicular to the axis of the piston.

  In the present invention, the main recess is constituted by three areas, so that the generation of the tumble flow is more reliable, and the tumble flow can be left until the piston reaches the ignition timing. It can contribute to improving output by promoting equalization.

That is, the air-fuel mixture is guided in the order of the first area, the third area, and the second area, but since the radius of curvature of the first area is the smallest, the sudden change of direction of the air-fuel mixture is ensured, and the first the radius of curvature of the three areas is very large us go with out flow rate decrease is suppressed, further, a second area for the radius of curvature smaller than the third area, the air-fuel mixture is smooth so as to be directed to the cylinder head in the second area Therefore, the smooth flow of the air-fuel mixture ensures the provision of the tumble flow.

In addition, since the generation of the tumble flow is ensured, a large kinetic energy is imparted to the air-fuel mixture, so that the tumble flow is continuously maintained near the ignition timing and the mixing of fuel and air is further promoted. the radius of curvature is very's go big, the air-fuel mixture will be subjected to strong crushing effect immediately before ignition timing, further mixed by the squashing action is also facilitated rapid flames spread while being accelerated.

  In this way, the series of behaviors of generating, sustaining and collapsing the tumble flow is performed efficiently, and the mixing of fuel and air is enhanced, and the uniform and high-speed flame propagation is promoted. It can contribute to improvement.

In addition, a squish surface is formed in an annular shape on the periphery of the piston, but the center of curvature of the third area of the main recess is closer to the exhaust port, so it is necessary for the third area and the second area . The squish surface can secure a necessary width while ensuring a necessary length, and therefore knocking can be effectively suppressed.

  If the squish area is too shallow, the effect of preventing knocking cannot be expected. Conversely, if the squish area is too deep, the flow of the air-fuel mixture may be hindered. In this respect, if the depth of the squish area and the depth of the main recess are set to approximately the same level as in claim 2, the necessary squish area can be secured while ensuring a large tumble flow, increasing combustion efficiency and preventing knocking. There is an advantage that can be achieved effectively.

  By the way, the reliability of the tumble flow generation is closely related to the depth of the main recess, and as the depth of the main recess increases, the flow rate of the tumble flow increases and the turbulent energy of the mixture increases, The flame propagation speed tends to increase. However, as a result of experiments by the inventors of the present application, when the main recess has a depth of, for example, twice the depth of the squish area, the turbulence promoting effect of the air-fuel mixture is noticeable, but the fuel efficiency is over A worsening phenomenon was observed. This is presumably because the surface area of the crown surface of the piston increases due to the deepening of the main recess, and the heat due to combustion escapes from the surface of the piston.

  That is, it can be said that increasing the depth of the main recess has the advantage of promoting tumble flow, but also has the problem of increased heat loss. In this regard, if the configuration of claim 2 of the present application is adopted, it is estimated that a tumble flow having a high flow rate can be generated without excessively increasing the surface area of the piston crown, but the output is increased while avoiding deterioration of fuel consumption. We were able to plan.

In addition, a sub-recess for releasing the exhaust valve may have to be formed at the location close to the exhaust port on the crown surface of the piston. If the main recess is brought close to the inner periphery of the squish surface, the main recess However, if a flat surface is provided as in claim 3, the main recess can be formed so as not to overlap the sub recess. And enjoy.

It is a vertical front view which shows embodiment, and is sectional drawing of the whole seen from the II view direction of FIG. 2 (A). (A) is a top view of a piston, (B) is a top view of a piston in the state which added the position of the inlet port and the exhaust port with the dotted line. It is a vertical front view which shows an effect | action.

  Next, an embodiment of the present invention will be described with reference to the drawings.

(1). Structure This embodiment is applied to a four-cycle internal combustion engine. The internal combustion engine covers a cylinder block 2 having a cylinder bore 1, a piston 3 fitted in the cylinder bore 1 so as to be reciprocally movable, and the cylinder bore 1. The cylinder head 4 is fixed to the cylinder block 2 as described above. The piston 3, the piston ring 5 and the oil ring 6 is fitted, connecting rod 7 is connected. FIG. 1 is a cross-sectional view seen from the axial direction of a crankshaft (not shown) so that it can be understood from the posture of the connecting rod 7.

The cylinder head 4 has a combustion chamber 8 that opens toward the cylinder bore 1. The combustion chamber 8 has become a concave cross-section base cone facing the cylinder bore 1, thus, (the or cylinder head 4) combustion chamber 8, an inclined roof surface 9 that is inclined relative to the axis O1 of the cylinder bore 1 The air inlet 11 that is opened and closed by the intake valve 10 and the air outlet 13 that is opened and closed by the exhaust valve 12 are arranged on the inclined roof surface 9 in such a way that they are distributed on both sides of the axis O1. Has been. At the center of the combustion chamber 8, is attached to the spark plug 14 as an example of the ignition means.

In FIG. 2, the arrangement direction of the intake port 11 and the exhaust port 13 is indicated by the symbol X, and the direction orthogonal to the X direction and the axis O1 of the cylinder bore 1 and the piston 3 is defined as the Y direction. The direction seen is the front view direction. Therefore, FIG.1 and FIG.3 displays the normal cross section containing the axial center O1, and this is defined as a vertical front view. The direction viewed from the X direction is defined as the side view direction. For convenience, the X direction is referred to as the left-right direction, and the Y direction is referred to as the front-rear direction. Since FIG. 1 is a view seen from the axial direction of the crankshaft, the Y direction is the same as the axial direction of the crankshaft.

A squish surface 15 that is inclined with respect to the axis 3 of the piston 3 and the cylinder bore 1 is formed on the periphery of the piston 3. Accordingly, a squish area 16 having a triangular cross section is formed in an annular shape outside the squish surface 15. The inclination angle of the squish surface 15 is set to be substantially the same as the inclination angle of the inclined roof surface 9 in the cylinder head 4. Further, the width dimension L of the squish surface 15 is about twice as large as the height dimension H1, and therefore the inclination angle of the squish surface 15 is about 30 ° (a little less than 30 °). The width L of the squish surface 15 is about 0.28 times the radius of the piston 3, and the height dimension (depth dimension of the squish area 16) H1 of the squish surface 15 is about 0.09 times the radius of the piston 3. It is set to about.

The site surrounded by the piston 3 sac out squish surface 15, the main recess 18 is formed. As shown in FIG. 2, the main recess 18 is formed so as to spread from the exhaust port 13 side toward the intake port 11 side. Further, two front and rear first sub-recesses 19 for allowing the intake valve 10 to escape and two front and rear second sub-recesses 20 for allowing the exhaust valve 12 to escape are formed on the crown surface of the piston 3. . The first sub-recess 19 overlaps the main recess 18 in a considerable range, but the second sub-recess 20 slightly overlaps the main recess 18.

The squish surface 15 is divided into two portions by the first sub-recess 19, but the second sub-recess 20 is located inside the squish surface 15, and the front and rear second sub-recesses 20 and the squish surface 15 are separated. slightly range surrounded by the main recess 18 is a flat surface 21 which is perpendicular to the axis O1 of the piston 3.

The main recess 18 includes a first area 22 near the exhaust port 13, a second area 23 near the intake port 11, and a third area located between the first area 22 and the second area 23. It consists of 24 three areas. In the longitudinal front view of FIGS. 1 and 3, the bottom surface (inner surface) of the first area 22 is an arc surface having a radius R1, and the bottom surface (inner surface) of the second area 23 is an arc surface having a radius R2. The bottom surface (inner surface) of 24 is an arc surface having a radius R3. R1 is 1.0 to 0.85 times the radius R0 of the cylinder bore 1, R2 is 2.5 to 4.0 times R1, and R3 is R3. It is set to several times R2 (for example, 3 to 5 times).

The first area 22 and the third area 24 are smoothly continuous, and the third area 24 and the second area 23 are also smoothly continuous. Center O2 of curvature of the third area A 2 4 is closer to the first area 22 than the shaft center O1 of the piston 3. The first area 22 is left-right width dimension of extent approximately the same as the third area 24, also the left and right width dimension of the second area 23, the left and right width dimension of the first area 22 and the third area 24 1 More than 5 times.

The main recess 18 has the deepest contact with the boundary between the first area 22 and the third area 24, and the depth dimension H <b> 2 is almost the same as the height dimension H <b> 1 of the squish surface 15. . Although not shown in the drawings, each of the areas 22, 23, and 24 is curved upwardly in a concave shape when viewed from the longitudinal side as viewed from the X direction.

(2) Summary As shown in FIG. 3 (A), the air-fuel mixture is sucked into the cylinder bore 1 during the intake stroke in which the piston 3 descends, and the intake valve port 10 is closed and the piston 3 turns into the ascending stroke. Qi is compressed. Although the air-fuel mixture ejected from the intake port 11 has linearity, the direction is changed downward by first colliding with the wall surface of the cylinder bore 1, and then guided by the main recess 18 of the piston 3 to be tumble flow Is given (turning energy is given).

In the present invention, since the radius of curvature of the first area 22 is small, the air-fuel mixture is efficiently redirected, and since the radius of curvature of the third area 24 is very large, the air-fuel mixture slows down. Without moving to the second area 23, the second area 23 is given a smooth upward direction. And guiding action in such a main recess 18, by the fact that the combustion chamber 8 of the cylinder head 4 is in the inclined roof surface 9, the air-fuel mixture, the piston as shown in FIG. 3 (B) in the compression stroke until 3 ignition timing near it has sustained tumble flow, thereby making it possible to improve the mixing of air and fuel.

Further, due to the fact that the radius of curvature of the third area 24 is very large and the main recess 18 is shallow as a whole, the crushing action of the air-fuel mixture near the ignition timing near the top dead center is firmly performed, The flame can be propagated quickly and evenly. Further, since the squish surface 15 can be secured without being excessive or insufficient, the effect of preventing knocking is also high.

  As in the embodiment, R1 is 1.0 to 0.85 times the radius R0 of the cylinder bore 1, R2 is 2.5 to 4.0 times R1, and R3 is several times R2 (for example, 3 to 5 times). When set, the generation of the tumble flow is more reliable and suitable.

Further, as in the present embodiment, when a slight range surrounded by the front and rear second sub-recesses 20, the squish surface 15 and the main recess 18 is made the flat surface 21, the piston 3 is turned over. In carrying, there is an advantage that the piston 3 can be maintained stably. Further, a second sub-recess 20 for allowing the exhaust valve 12 to escape is formed in a portion of the crown surface of the piston 3 that is close to the intake port 11, but the main recess 18 is temporarily extended to the inner peripheral edge of the squish surface 15. The main recess 18 and the second sub-recess 20 overlap with each other, but a slight amount surrounded by the front and rear second sub-recesses 20, the squish surface 15 and the main recess 18 as in the present embodiment. When the range is formed on the flat surface 21, the main recess 18 can be formed so as not to overlap the second sub-recess 20, so that it is considered that the effect of generating the tumble flow by the main recess 18 can be enjoyed firmly. These points are also one of the advantages of this embodiment.

(3). Others The present invention can be embodied in various ways other than the above embodiment. For example, the intake port 11 and the exhaust port 13 may be a single method instead of a double method. It is also possible to make the cross-sectional shape of the roof surface of the combustion chamber in the cylinder head a curved surface (that is, to form the combustion chamber in a bowl shape).

  The present invention can be applied to an internal combustion engine to exhibit its usefulness. Therefore, it can be used industrially.

DESCRIPTION OF SYMBOLS 1 Cylinder bore 2 Cylinder block 3 Piston 4 Cylinder head 8 Combustion chamber 9 Inclined roof surface 10 Intake port valve 11 Inlet port 12 Exhaust valve 13 Exhaust port 14 Spark plug 15 Squish surface 16 Squish area 18 Main recess
20 Sub-recess on the exhaust side
21 Flat surface 22 1st area 23 2nd area 24 3rd area

Claims (3)

A piston disposed reciprocally in the cylinder bore, and a cylinder head for closing the cylinder bore;
The cylinder head is formed with a combustion chamber having a substantially trapezoidal cross section having a roof surface inclined with respect to the axis of the cylinder bore, and is opened and closed by an intake valve on the inclined roof surface of the combustion chamber. While the intake port and the exhaust port that is opened and closed by the exhaust valve are opened so as to be located on the opposite side across the shaft center, an ignition plug is disposed at substantially the center of the combustion chamber,
The air-fuel mixture jetted from the intake port to the crown surface of the piston is viewed from the front as viewed from the direction orthogonal to the direction in which the exhaust port and the intake port are aligned and orthogonal to the axis of the piston. The main recess that gives the swirl flow is formed,
An internal combustion engine
Wherein the inner peripheral edge of the crown surface of the piston squish surface inclined relative to the axis is formed in an annular shape, the inside of the front Symbol squish surface, formed as the main recess is surrounded by the squish surface The main recess is configured to expand along the squish surface from the side close to the exhaust port toward the side close to the intake port, and the main recess is the side close to the exhaust port. Consists of three areas: a first area located on the side, a second area located on the side close to the intake port, and a third area located between the first area and the second area,
Said inner surface of each area is curved in a longitudinal sectional front view, these are the radius of curvature of the inner surface of each area, the longitudinal front view, the curvature of the first area radius is rather smaller than the curvature radius of the second area, the the radius of curvature of the three areas has become a relationship is several times the radius of curvature of the front Stories second area,
Further, the boundary between the first area and the third area is deepest, and the first area and the third area, and the second area and the third area are smoothly continuous, and the curvature of the third area is The center of is closer to the exhaust port than the axis of the piston,
And each said area is curving so that it may become concave toward a cylinder head also in the vertical side view perpendicular to the vertical front view,
Internal combustion engine. The dimension of the squish surface measured in the axial direction of the piston and the depth dimension of the deepest part of the main recess are set to be substantially the same.
The internal combustion engine according to claim 1. While the two exhaust ports are arranged side by side in the axial direction of the crankshaft, each is opened and closed by an exhaust valve,
Two sub-recesses corresponding to the exhaust valve are formed in a portion of the crown surface of the piston close to the exhaust port in a state of being located inside the squish surface. The area surrounded by the squish surface and the main recess is a flat surface perpendicular to the axis of the piston,
The internal combustion engine according to claim 1 or 2.

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