JP7196405B2 - direct injection engine - Google Patents

Description

The present invention relates to direct injection engines, and more particularly to the structure of combustion chambers and intake ports.

2. Description of the Related Art In direct injection engines for vehicles, air is blown into a combustion chamber through an intake port, and fuel is injected from a fuel injection valve provided on the ceiling surface to form an air-fuel mixture in the combustion chamber.

Improvements in thermal efficiency are required for such direct injection engines. As one measure for improving thermal efficiency, it is important to reduce cooling loss. In order to reduce the cooling loss, the technique disclosed in Patent Document 1 provides an air layer between the crown surface of the piston and the air-fuel mixture so that the air-fuel mixture does not come into direct contact with the crown surface of the piston. A configuration is disclosed.

Patent Literature 1 states that an air layer provided between the crown surface of the piston and the air-fuel mixture functions as a heat insulating layer to improve thermal efficiency.

JP 2013-194712 A

However, in a direct injection engine, the air introduced into the combustion chamber from the intake port advances toward the exhaust port opening side and forms a positive tumble flow in the combustion chamber. Losses increase, making it difficult to further improve thermal efficiency.

The present invention has been made to solve the above-mentioned problems, and aims to further improve thermal efficiency by reducing cooling loss by generating an appropriate tumble flow in the combustion chamber. To provide a direct injection engine capable of

A direct-injection engine according to one aspect of the present invention is a direct-injection engine having a cylinder that forms a combustion chamber, and has an intake-side inclined surface that is inclined from the top toward the intake side, and an exhaust that is inclined toward the exhaust side. A ceiling surface that forms the ceiling of the combustion chamber, and a crown surface that slides in the cylinder in the cylinder axial direction, and the crown surface is the cylinder axial direction of the combustion chamber. A piston that constitutes a lower surface and has a cavity recessed downward in the cylinder axis direction in a region of the crown surface where the cylinder axis intersects, and an intake side opening that opens in the intake side inclined surface. an intake port connected to the combustion chamber at the intake side opening; an exhaust port having an exhaust side opening opened in the exhaust side inclined surface and connected to the combustion chamber at the exhaust side opening; a fuel injection valve provided to face the combustion chamber from the ceiling, and when the intake port is viewed from above in the axial direction of the cylinder, the central axis of the intake port extends from the intake side opening to the air. A predetermined region on the upstream side in the flow direction of the cylinder is disposed so as to face radially outward of the cylinder with respect to an axis passing through the central axis of the cylinder and along the intake and exhaust direction, and perpendicular to the cylinder axis. , the inclination angle formed by the exhaust-side inclined surface with respect to the virtual plane is smaller than the inclination angle formed by the intake-side inclined surface with respect to the virtual plane, and the fuel injection fuel is injected from the valve into the combustion chamber in the latter half of the compression stroke in a predetermined engine load range, and the crown surface of the piston is a peripheral edge of the cavity and faces the intake-side inclined surface; An intake-side inclined surface inclined with respect to the virtual plane and an exhaust-side inclined surface opposed to the exhaust-side inclined surface and inclined with respect to the virtual plane, the exhaust-side inclined surface with respect to the virtual plane The inclination angle formed by the slope portion is smaller than the inclination angle formed by the intake-side slope portion with respect to the virtual plane.

In the direct-injection engine according to the above aspect, the region of the center axis of the intake port from the upstream side in the air flow direction to the intake-side opening is arranged to face radially outward with respect to the axis of the cylinder. Therefore, the air introduced into the combustion chamber from the intake side opening advances radially outward of the cylinder. Then, in the combustion chamber, the introduced air hits the inner peripheral surface of the cylinder, swirls, and advances toward the center of the combustion chamber. Therefore, in the direct injection engine according to the aspect described above, it is possible to generate a positive tumble flow that swirls slightly in the combustion chamber.

In addition, in the direct injection engine according to the above aspect, by applying the introduced air to the inner peripheral surface of the cylinder, the strength of the normal tumble flow can be weakened, and the reverse tumble flow (from the intake side opening to the exhaust side) can be reduced. can promote vortex diffusion in relation to the tumble flow generated by air introduced in the opposite direction ). Therefore, in the direct injection engine according to the aspect described above, it is possible to stratify the air-fuel mixture in the central portion of the combustion chamber.

Further, in the direct injection engine according to the aspect described above, since the inclination angle of the exhaust-side inclined surface with respect to the virtual plane is set smaller than the inclination angle of the intake-side inclined surface with respect to the virtual plane, combustion occurs from the intake-side opening. The air introduced into the room separates from the exhaust-side inclined surface. That is, in the direct-injection engine according to the above aspect, by setting the inclination angle of the exhaust-side inclined surface as described above, the air introduced from the intake-side opening toward the exhaust side flows along the exhaust-side inclined surface. It becomes difficult and can generate positive tumble flow with small swirl. As a result, in the direct injection engine according to the above aspect, the strength of the forward tumble flow and the reverse tumble flow can be balanced in the combustion chamber, and the air-fuel mixture can be stratified in the central portion of the combustion chamber. becomes.
Further, in the direct-injection engine according to the above aspect, the inclination angle formed by the exhaust-side slope portion with respect to the virtual plane on the crown surface of the piston is smaller than the inclination angle formed by the intake-side slope portion with respect to the virtual plane. Since this is set, the horizontal component (component perpendicular to the cylinder axis) of the squish flow generated during the compression stroke is larger on the exhaust side than on the intake side. Therefore, in the direct injection engine according to the aspect described above, by adjusting the strength of the squish flow as described above, it is possible to further improve the strength balance between the forward tumble flow and the reverse tumble flow.

Therefore, in the direct injection engine according to the aspect described above, by generating an appropriate tumble flow in the combustion chamber, it is possible to reduce the cooling loss, thereby further improving the thermal efficiency.

Note that the "intake and exhaust direction" in the above aspect is the direction connecting the center of the intake side opening and the center of the exhaust side opening within a virtual plane perpendicular to the cylinder axis. In addition, when two intake side openings and two exhaust side openings are provided per cylinder, and the interval between the two intake side openings and the interval between the two exhaust side openings are different. In , it is the direction connecting the midpoint between the two intake side openings and the midpoint between the two exhaust side openings.

A direct-injection engine according to another aspect of the present invention is the aspect described above, wherein the intake-side inclined surface of the crown surface of the piston is along the intake-side inclined surface of the ceiling surface, and the The exhaust-side inclined surface on the crown surface is along the exhaust-side inclined surface on the ceiling surface.

In the direct-injection engine according to the above aspect, the intake-side inclined surface of the piston and the intake-side inclined surface of the ceiling surface are aligned with each other, and the exhaust-side inclined surface of the piston and the exhaust-side inclined surface of the ceiling surface are also aligned with each other. It is superior in generating a squish flow during stroke. Also, in the direct injection engine according to the above aspect, the strength of the squish flow from the exhaust side and the squish flow from the intake side are adjusted, so that the strength balance between the forward tumble flow and the reverse tumble flow is further improved. It becomes possible to
A direct-injection engine according to another aspect of the present invention is the aspect described above, wherein the intake port is a first independent intake port that is continuous with the combustion chamber at a first intake-side opening opened in the intake-side inclined surface. and a second independent intake port connected to the combustion chamber at a second intake-side opening opened with a gap from the first intake-side opening with respect to the intake-side inclined surface, When the first independent intake port and the second independent intake port are viewed in plan from the axial direction of the cylinder, the central axis of the first independent intake port extends from the upstream side in the air flow direction to the first intake side opening. The region between the , the region from the upstream side in the air flow direction to the second intake side opening faces the other outside in the radial direction of the cylinder with respect to the axis passing through the central axis of the cylinder and along the intake and exhaust direction. are arranged.
In the direct-injection engine according to the above aspect, the center axis of the first independent intake port and the center axis of the second independent intake port are configured to face outward, which are opposite to each other in the radial direction of the cylinder. The air introduced into the combustion chamber from the first intake side opening and the combustion chamber from the second intake side opening
Each of the air introduced into and hits the inner peripheral surface of the cylinder and swirls in a state having components facing each other. Therefore, in the direct injection engine according to the aspect described above, the forces of the two normal tumble flows cancel each other out, which is more advantageous in promoting the diffusion of the vortex.
A direct-injection engine according to another aspect of the present invention is a direct-injection engine having cylinders forming a combustion chamber, and includes an intake-side inclined surface inclined from the top toward the intake side and an exhaust inclined toward the exhaust side. A ceiling surface that forms the ceiling of the combustion chamber, and a crown surface that slides in the cylinder in the cylinder axial direction, and the crown surface is the cylinder axial direction of the combustion chamber. A piston that constitutes a lower surface and has a cavity recessed downward in the cylinder axis direction in a region of the crown surface where the cylinder axis intersects, and an intake side opening that opens in the intake side inclined surface. an intake port connected to the combustion chamber at the intake side opening; an exhaust port having an exhaust side opening opened in the exhaust side inclined surface and connected to the combustion chamber at the exhaust side opening; a fuel injection valve provided to face the combustion chamber from the ceiling, and when the intake port is viewed from above in the axial direction of the cylinder, the central axis of the intake port extends from the intake side opening to the air. A predetermined region on the upstream side in the flow direction of the cylinder is disposed so as to face radially outward of the cylinder with respect to an axis passing through the central axis of the cylinder and along the intake and exhaust direction, and perpendicular to the cylinder axis. , the inclination angle formed by the exhaust-side inclined surface with respect to the virtual plane is smaller than the inclination angle formed by the intake-side inclined surface with respect to the virtual plane, and the fuel injection Fuel is injected from the valve into the combustion chamber in the latter half of the compression stroke in a predetermined engine load range, and the intake port is injected into the combustion chamber at a first intake-side opening opened on the intake-side inclined surface. a continuous first independent intake port, and a second independent intake that is continuous with the combustion chamber at a second intake-side opening that is opened with a gap from the first intake-side opening with respect to the intake-side inclined surface and a port, and when the first independent intake port and the second independent intake port are viewed from above in the axial direction of the cylinder, the center axis of the first independent intake port extends from the upstream side in the direction of air flow. A region extending to the first intake side opening is disposed so as to face one outer side in the radial direction of the cylinder with respect to an axis passing through the central axis of the cylinder and extending in the intake and exhaust direction, and the second The central axis of the independent intake port is such that a region from the upstream side in the air flow direction to the second intake side opening is in the radial direction of the cylinder with respect to an axis passing through the central axis of the cylinder and extending in the intake and exhaust direction. It is arranged to face the other outside, and the exhaust port is opened to the exhaust side inclined surface A first independent exhaust port connected to the combustion chamber at a first exhaust-side opening, and a second exhaust-side opening opened with a gap between the first exhaust-side opening and the exhaust-side inclined surface. a second independent exhaust port continuous with the combustion chamber at
wherein the crown surface of the piston has a portion below the first intake side opening in the cylinder axial direction and a portion below the second intake side opening in the cylinder axial direction and a plane portion between the intake valves along the virtual plane, a portion below the first exhaust side opening in the cylinder axial direction, and a portion between the second exhaust side opening and an inter-exhaust-valve plane portion along the virtual plane in a region between the lower portion in the cylinder axial direction.
In the direct-injection engine according to the above aspect, the region of the center axis of the intake port from the upstream side in the air flow direction to the intake-side opening is arranged to face radially outward with respect to the axis of the cylinder. Therefore, the air introduced into the combustion chamber from the intake side opening advances radially outward of the cylinder. Then, in the combustion chamber, the introduced air hits the inner peripheral surface of the cylinder, swirls, and advances toward the center of the combustion chamber. Therefore, in the direct injection engine according to the aspect described above, it is possible to generate a positive tumble flow that swirls slightly in the combustion chamber.
In addition, in the direct injection engine according to the above aspect, by applying the introduced air to the inner peripheral surface of the cylinder, the strength of the normal tumble flow can be weakened, and the reverse tumble flow (from the intake side opening to the exhaust side) can be reduced. can promote vortex diffusion in relation to the tumble flow generated by the air introduced into the reverse stem). Therefore, in the direct injection engine according to the aspect described above, it is possible to stratify the air-fuel mixture in the central portion of the combustion chamber.
Further, in the direct injection engine according to the aspect described above, since the inclination angle of the exhaust-side inclined surface with respect to the virtual plane is set smaller than the inclination angle of the intake-side inclined surface with respect to the virtual plane, combustion occurs from the intake-side opening. The air introduced into the room separates from the exhaust-side inclined surface. That is, in the direct-injection engine according to the above aspect, by setting the inclination angle of the exhaust-side inclined surface as described above, the air introduced from the intake-side opening toward the exhaust side flows along the exhaust-side inclined surface. It becomes difficult and can generate positive tumble flow with small swirl. As a result, in the direct injection engine according to the above aspect, the strength of the forward tumble flow and the reverse tumble flow can be balanced in the combustion chamber, and the air-fuel mixture can be stratified in the central portion of the combustion chamber. becomes.
Further, in the direct injection engine according to the aspect described above, the center axis of the first independent intake port and the center axis of the second independent intake port are configured to face outward, which are opposite to each other in the radial direction of the cylinder. Therefore, the air introduced into the combustion chamber through the first intake-side opening and the air introduced into the combustion chamber through the second intake-side opening each hit the inner peripheral surface of the cylinder and have components facing each other. turn in the state. Therefore, in the direct injection engine according to the aspect described above, the forces of the two normal tumble flows cancel each other out, which is more advantageous in promoting the diffusion of the vortex.
In addition, in the direct injection engine according to the above aspect, since the planar portion between the intake valves and the planar portion between the exhaust valves are provided on the crown surface of the piston as described above, the planar portion between the intake valves and the planar portion between the exhaust valves are provided during the compression stroke. The generation of squish flow between the head and the ceiling surface is suppressed. Therefore, in the direct injection engine according to the aspect described above, it is possible to suppress the occurrence of turbulence in the stratified air-fuel mixture during the process from the compression stroke to the combustion.
Therefore, in the direct injection engine according to the aspect described above, by generating an appropriate tumble flow in the combustion chamber, it is possible to reduce the cooling loss, thereby further improving the thermal efficiency.
A direct injection engine according to another aspect of the present invention is the aspect described above, wherein the crown surface of the piston is a peripheral edge of the cavity, faces the intake-side inclined surface, and is inclined with respect to the virtual plane. and an exhaust-side inclined surface facing the exhaust-side inclined surface and inclined with respect to the virtual plane, and the inclination angle formed by the exhaust-side inclined surface with respect to the virtual plane is , is smaller than the inclination angle formed by the intake-side slope portion with respect to the virtual plane.
In the direct-injection engine according to the aspect, the inclination angle formed by the exhaust-side slope portion with respect to the virtual plane is set smaller than the inclination angle formed by the intake-side slope portion with respect to the virtual plane on the crown surface of the piston. Therefore, the horizontal component (component perpendicular to the cylinder axis) of the squish flow generated during the compression stroke is larger on the exhaust side than on the intake side. Therefore, in the direct injection engine according to the aspect described above, by adjusting the strength of the squish flow as described above, it is possible to further improve the strength balance between the forward tumble flow and the reverse tumble flow.

A direct injection engine according to another aspect of the present invention is the aspect described above, wherein fuel is intermittently supplied from the fuel injection valve to the combustion chamber in the latter half of the compression stroke in the predetermined engine load region. Injected multiple times.

In the direct injection engine according to the above aspect, since the fuel injection is intermittently performed multiple times in the latter half of the compression stroke, the injection speed of the fuel injection does not become too fast, and the injected fuel directly hits the crown surface of the piston. Contact can be suppressed, and cooling loss can be further reduced.

A direct-injection engine according to another aspect of the present invention is the aspect described above, further comprising an intake valve for opening and closing the intake-side opening, the intake valve passing through the upper wall of the intake port, and a shaft portion inserted into a port; and a head portion provided at a tip portion of the shaft portion on the side of the combustion chamber. A portion adjacent to the portion through which the portion is inserted on the upstream side in the air flow direction is formed with an inclined surface so as to face the intake side opening portion.

In the direct-injection engine according to the above aspect, since the adjacent portion of the inner surface of the intake port forms the inclined surface, the flow of air introduced into the combustion chamber from the intake-side opening is directed in the axial direction of the cylinder. It can be directed downward, which is more advantageous for creating a positive tumble flow with small swirls.

A direct injection engine according to another aspect of the present invention is the aspect described above, wherein the portion of the intake port formed by the inclined surface of the inner surface is upstream of the portion in the air flow direction. It is connected to the part by a smooth curved surface.

In the direct-injection engine according to the above-described aspect, the portion formed with the inclined surface and the portion on the upstream side of the inner surface of the intake port are formed with smooth curved surfaces. Air flow loss can be suppressed.

In the direct-injection engine according to each aspect described above, by generating an appropriate tumble flow in the combustion chamber, it is possible to reduce cooling loss and further improve thermal efficiency.

1 is a schematic cross-sectional view showing the configuration of a direct injection engine according to Embodiment 1. FIG. FIG. 2 is a schematic plan view showing the configuration of cylinders in a direct injection engine; FIG. 3 is a schematic cross-sectional view showing the configuration of the ceiling surface in the combustion chamber; FIG. 3 is a schematic cross-sectional view showing the configuration of an intake port; FIG. 5 is a view showing a VV cross section in FIG. 4, and is a schematic cross-sectional view showing a portion of the independent intake port provided with an inclined surface. FIG. 3 is a view showing the VI-VI cross section of FIG. 2, and is a schematic cross-sectional view showing the configuration of the outer edge portion of the ceiling surface and the outer edge portion of the piston crown surface. It is a model top view which shows a piston crown surface. FIG. 3 is a schematic diagram showing the flow of air in the combustion chamber; FIG. 4 is a schematic diagram showing a squish flow generated during a compression stroke; It is a schematic cross section which shows a partial structure of a fuel injection valve. It is a timing chart showing a fuel injection period. FIG. 4 is a schematic diagram showing a state of injected fuel into a cavity of a piston; FIG. 7 is a schematic plan view showing the configuration of cylinders in a direct injection engine according to Embodiment 2;

EMBODIMENT OF THE INVENTION Below, embodiment of this invention is described, considering drawing into consideration. The embodiment described below is one embodiment of the present invention, and the present invention is not limited to the following embodiments except for its essential configuration.

In the drawings used below, "In" indicates the intake side, "Ex" indicates the exhaust side, "Up" indicates the upper side in the axial direction of the cylinder, "Lo" indicates the lower side in the axial direction of the cylinder, and "OP ₁ ” indicates one side in the direction of the engine output shaft, and “OP ₂ ” indicates the other side in the direction of the engine output shaft.

[Embodiment 1]
1. Configuration of Direct Injection Engine 1 The configuration of a direct injection engine (hereinafter simply referred to as "engine") 1 according to the present embodiment will be described with reference to FIGS. 1 and 2. FIG.

As shown in FIG. 1, an engine 1 includes a cylinder block 2 and a cylinder head 3. As shown in FIG. A combustion chamber 10 is formed in the cylinder block 2 for each cylinder 1a. A cylindrical cylinder liner 5 is fitted in the cylinder block 2 . The inner periphery of the cylinder liner 4 constitutes the side peripheral surface of the combustion chamber 10 .

A piston 5 is disposed inside the cylinder liner 4 so as to be slidable in the vertical direction (Up-Lo direction). A crown surface 5b of the piston 5 is provided with a cavity 5a recessed downward (Lo side) in the cylinder axial direction. The layout of the cavity 5a with respect to the crown surface 5b of the piston 5 will be described later.

A connecting rod (connecting rod) 18 is connected to the piston 5 . The connecting rod 18 is connected to an engine output shaft (not shown) at the lower side (Lo side) in the cylinder axial direction.

The cylinder head 3 is provided with an intake port 6 on the intake side (In side) and an exhaust port 7 on the exhaust side (Ex side). As shown in FIG. 2, the intake port 6 is constructed by combining independent intake ports 61 and 62 and a collective intake port 63 .

The independent intake port 61 is connected to the combustion chamber 10 at the intake port opening 6a, and the independent intake port 62 is connected to the combustion chamber 10 at the intake port opening 6b. The collective intake port 63 is a portion where the independent intake port 61 and the independent intake port 62 are gathered on the intake side (In side).

As shown in FIG. 2, the exhaust port 7 has independent exhaust ports 71 and 72 . The independent exhaust port 71 is continuous with the combustion chamber 10 at the exhaust port opening 7a. The independent exhaust port 72 is continuous with the combustion chamber 10 at the exhaust port opening 7b.

Next, as shown in FIG. 2, a fuel injection valve 15 is attached to the cylinder head 3 at a location that coincides with the cylinder axis Ax _1a , that is, at the center of the cylinder 1a.

In FIG. 2, an imaginary line Ax _1Y passing through the cylinder axis Ax _1a and extending in the engine output shaft direction (OP ₁ -OP ₂ direction) is drawn. Spark plugs 16 and 17 are attached to the cylinder head 3 at respective positions on the imaginary line Ax _1Y with the fuel injection valve 15 interposed therebetween. One of the spark plugs 16, 17 is an arc discharge plug and the other is a low temperature plasma plug.

It should be noted that plugs having the functions of an arc discharge plug and a low temperature plasma plug may be adopted as the spark plugs 16 and 17, respectively.

Returning to FIG. 1, in the cylinder head 3, the valve seats 8 are fitted into the intake port openings 6a and 6b (in FIG. 1, only the valve seats 8 fitted into the intake port openings 6a are shown). , a valve seat 9 is fitted into the exhaust port openings 7a and 7b (in FIG. 1, only the valve seat 8 fitted into the exhaust port opening 7a is shown).

Further, the cylinder head 3 is provided with intake valves 11 for opening and closing the intake port openings 6a and 6b (only the intake valves 11 for opening and closing the intake port openings 6a are shown in FIG. 1), and exhaust port openings are provided. An exhaust valve 12 for opening and closing the portions 7a and 7b is provided (only the exhaust valve 11 for opening and closing the exhaust port opening portion 7a is shown in FIG. 1).

The intake valve 11 is composed of a head portion 11a and a shaft portion 11b, and the shaft portion 11b is slidable inside a cylindrical valve guide 13 in the vertical direction (Up-Lo direction). The exhaust valve 12 is also composed of a head portion 12a and a shaft portion 12b, and the shaft portion 12b is slidable in the vertical direction (Up-Lo direction) inside a similarly cylindrical valve guide 14. .

As shown in FIG. 1, the combustion chamber 10 of the cylinder 1a includes a ceiling surface 3a that is a surface on the lower side (Lo side) of the cylinder head 3, a lower surface of the head portion 11a of the intake valve 11, and a head surface of the exhaust valve 12. The combustion chamber is surrounded by the lower surface of the portion 12a, the inner peripheral surface 4a of the cylinder liner 4, and the crown surface 5b of the piston 5, and is a pent roof type combustion chamber.

2. Arrangement Form of Independent Intake Ports 61 and 62 in Intake Port 6 The arrangement form of the independent intake ports 61 and 62 in the intake port 6 will be described with reference to FIG.

As shown in FIG. 2, a virtual line Ax _1X is drawn from the cylinder axis Ax _1a in the intake/exhaust direction (In-Ex direction). At this time, the independent intake port 61 is provided with its center axis Ax ₆₁ inclined at an angle θ ₆₁ with respect to the imaginary line Ax _1X . In other words, in the present embodiment, the central axis Ax ₆₁ of the independent intake port 61 is directed from the connection side with the collective intake port 63 to the side of the intake port opening 6a toward the outer side (OP ₁ ) in the cross-sectional radial direction of the cylinder 1a. side) is actively (intentionally) configured to be oriented.

On the other hand, the independent intake port 62 is provided with its central axis Ax ₆₂ inclined at an angle θ ₆₂ with respect to the virtual line Ax _1X . In other words, in the present embodiment, the central axis Ax ₆₂ of the independent intake port 62 is directed from the connection side with the collective intake port 63 to the side of the intake port opening 6b toward the outer side (OP ₂ ) in the cross-sectional radial direction of the cylinder 1a. side) is actively (intentionally) configured to be oriented.

In the engine 1 having the independent intake ports 61 and 62 arranged as described above, when the intake valve 11 is in the open state, air flows are formed as indicated by arrows F ₁ to F ₁₃ in FIG. be. That is, the air F ₁ flowing through the collective intake port 63 is divided into the independent intake port 61 and the independent intake port 62 (F ₂ , F ₃ ). _The air F2 flows along the central axis Ax ₆₁ of the independent intake port 61 toward the intake port opening 6a. Similarly _, air F3 flows along the central axis Ax ₆₂ of the independent intake port 62 toward the intake port opening 6b.

_Part of the air F2 that has reached the intake port opening 6a is led out along the upper surface of the head portion 11a of the intake valve 11 toward the exhaust side (Ex side) of the combustion chamber ₁₀ (F4), Part of it is led out to the opposite side (In side) (F ₈ ). Similarly, the air F2 that has reached the intake port opening 6b is partly led out to the exhaust side (Ex side) of the combustion chamber 10 along the upper surface of the head portion 11a of the intake valve ₁₁ (F ₉ ), part of which is led to the opposite side (In side) (F ₁₃ ).

The air F4 led out to the combustion chamber ₁₀ from the intake port opening 6a advances toward the exhaust side (Ex side) and _one side (OP1 side) in the direction of the engine output shaft ₍ F5). . Then, the air F5 _hits the inner peripheral surface 4a of the cylinder liner ₄ (F6) and changes direction to the other side (OP2 _side ) of the engine output shaft direction ( _F7 ).

On the other hand, the air F9 introduced into the combustion chamber ₁₀ from the intake port opening 6b advances toward the exhaust side (Ex side) and the other side (OP2 _side ) in the direction of the engine output shaft (F ₁₀ ). Then, the air F ₁₀ hits the inner peripheral surface 4a of the cylinder liner 4 (F ₁₁ ) and changes direction to one side (OP ₁ side) in the direction of the engine output shaft (F ₁₂ ).

In the engine 1 according to the present embodiment, the air F4 introduced into the combustion chamber 10 through the intake port opening 6a and the air F9 introduced into the combustion chamber ₁₀ through the intake port opening 6b flow into the cylinder liner ₄ . changes its direction (F ₆ , F ₁₁ ) by hitting the inner peripheral surface of , and has components facing each other (F ₉ , F ₁₂ ).

As described above, in the cylinder 1a of the engine 1, the strength of the positive tumble flow in the combustion chamber 10 can be weakened, small vortices can be formed, and the air-fuel mixture in the central portion of the combustion chamber 10 can be stratified. can.

3. Configuration of Ceiling Surface 3a in Combustion Chamber 10 The configuration of the ceiling surface 3a in the combustion chamber 10 of the engine 1 will be described with reference to FIG. FIG. 3 is a schematic cross-sectional view showing the configuration of the ceiling surface 3a in the combustion chamber 10. As shown in FIG.

As shown in FIG. 3, in the cylinder head 3, the intake air is inclined downward (Lo side) in the cylinder axis direction from the cylinder axis Ax _1a (corresponding to the top) toward the intake side (In side). a side inclined surface 3d, an exhaust-side inclined surface 3e that inclines downward (Lo side) in the cylinder axis direction from the cylinder axis Ax _1a (corresponding to the top) toward the exhaust side (Ex side); is formed.

At locations where the intake port openings 6a and 6b (only the intake port opening 6a is shown in FIG. 3) are opened, the Lo-side portions of the intake port openings 6a and 6b match the intake side inclined surface 3d. . Similarly, at locations where the exhaust port openings 7a and 7b (only the exhaust port opening 7a is shown in FIG. 3) are opened, the Lo-side portions of the exhaust port openings 7a and 7b are the exhaust-side inclined surfaces 3e. matches

Here, as shown in FIG. 3, the center axis Ax ₁₁ of the intake valve 11 (not shown in FIG. ₃ ) passes through the intersection point P1 of the intake-side inclined surface 3d and is perpendicular to the cylinder axis Ax _1a . Assume _a virtual plane L1. Similarly, a virtual plane L2 passing through the intersection P2 between the central axis Ax12 of the exhaust valve ₁₂ (not shown in _FIG . 3) and the exhaust-side inclined surface 3e and perpendicular to the cylinder axis _Ax1a is assumed.

The inclination angle formed by the intake _- side inclined surface 3d with respect to the virtual plane L1 is defined as _θIn , and the inclination angle formed by the exhaust _- side inclined surface 3e with respect to the virtual plane L2 is defined as _θEx . At this time, the engine 1 satisfies the following relationship.

θ _Ex < θ _In (Equation 1)
That is, in the engine 1 according to the present embodiment, the combustion chamber 10 is provided with the ceiling surface 3a having the intake-side inclined surface 3d and the exhaust-side inclined surface 3e with different inclinations.

4. Configuration of Intake Port 6 The configuration of the intake port 6 will be described with reference to FIGS. 4 and 5. FIG. 4 is a schematic cross-sectional view showing the configuration of the intake port 6, and FIG. 5 is a schematic cross-sectional view showing a VV cross section of FIG. Note that FIG. 4 shows only a portion (independent intake port 61) of the intake port 6 connected to the intake port opening 6a. In FIG. 4, of the wall surfaces surrounding the intake port 6, the upper wall surface is defined as an upper surface 6c, and the lower wall surface is defined as a lower surface 6d.

5, one of the independent intake ports 61 and 62 is extracted and illustrated.

As shown in FIG. 4, the intake port 6 of the engine 1 is provided with a valve guide 13 passing through the upper surface 6c. The valve guide 13 is arranged so that the central axis Ax ₁₁ of the intake valve 11 (not shown in FIG. 4) is directed to the radial center of the intake port opening 6a.

As shown in part A of FIG. 4, the upper surface 6c of the intake port 6 is provided with an inclined surface 6e on the upstream side (upstream side of the air flow) of the portion where the valve guide 13 protrudes. When drawing an imaginary line (imaginary extension line) L _{6 e} obtained by extending a tangent line contacting the inclined surface 6 e , the imaginary extension line L _{6 e points toward} the central axis Ax ₁₁ of the intake valve 11 .

More specifically, the imaginary extension line L _{6 e} intersects the central axis Ax ₁₁ of the intake valve 11 between the upper surface 8 a and the lower surface 8 b of the valve seat 8 .

That is, the inclined surface 6e of the intake port 6 is steeper than the portion of the upper surface 6c on the upstream side of the inclined surface 6e. In addition, the inclined surface 6e is configured with a smooth curved surface with respect to a portion on the upstream side of the portion of the upper surface 6c where the inclined surface 6e is provided.

The independent intake port 62 connected to the intake port opening 6b also has the same configuration as described above.

As shown in FIG. 5, in the intake port 6, an inclined surface 6e is formed along the outer peripheral surface of the valve guide 13 in a conical shape. As shown in FIG. 2, the independent intake ports 61 and 62 are provided with their central axes Ax ₆₁ and Ax ₆₂ inclined at angles θ ₆₁ and θ ₆₂ with respect to the virtual line Ax _1X . , the air passage portion 6f formed on the side opposite to the imaginary line Ax _1X side with respect to the portion provided with the inclined surface 6e has a narrow passage width in the engine output shaft direction (OP ₁ -OP ₂ direction). , the flow velocity of the air F ₁₄₀ passing through the passage portion 6f increases.

On the other hand, the air passage portion 6g formed on the imaginary line Ax _1X side with respect to the portion provided with the inclined surface 6e is a passage in the direction of the engine output shaft (OP ₁ -OP ₂ direction) than the passage portion 6f. The width is wide, and the flow velocity of the air _F141 passing through the passage portion 6g is relatively lowered.

It should be noted that the same plane as the inclined surface 6e may be formed on the virtual line Ax _1X side, or the inclined plane 6e may be formed on the side opposite to the virtual line Ax _1X side in the direction of the engine output shaft (OP ₁ -OP ₂ direction). It is good also as forming the same plane as the surface 6e.

5. Outer edge portions 3b, 3c and outermost edge portions 3e, 3f of the ceiling surface 3a, and outer edge portions 5c, 5d and outermost edge portions 5e, 5f of the piston 5
Each form of the outer edge portions 3b, 3c and the outermost edge portions 3e, 3f of the ceiling surface 3a and the outer edge portions 5c, 5d and the outermost edge portions 5e, 5f of the piston 5 will be described with reference to FIG. FIG. 6 is a schematic cross-sectional view showing the VI-VI cross section of FIG.

As shown in FIG. 6, the outer edges 3b and 3c of the ceiling surface 3a are curved and gently inclined. That is, the outer edge portions 3b and 3c are sloped more gently than the intake-side inclined surface 3d and the exhaust-side inclined surface 3e.

In addition, the outermost edge portion 3e on the OP ₁ side of the outer edge portion 3b and the outermost edge portion 3f on the OP ₂ side of the outer edge portion 3c are positioned higher than the outer edge portions 3b and 3c, the intake-side inclined surface 3d, and the exhaust-side inclined surface 3e. It has a rising slope.

In the crown surface 5b of the piston 5, the outer edges 5c and 5d of the portion where the cavity 5a is provided are formed with gently curved surfaces along the outer edges 3b and 3c of the ceiling surface 3a.

Also, on the crown surface 5b of the piston 5, the outermost edge portion 5e radially outward from the outer edge portion 5c and the outermost edge portion 5f radially outward from the outer edge portion 5d are aligned with the outermost edge portions 3e and 3f of the ceiling surface 3a. It is an inclined surface that rises along.

In this manner, the outer edges 3b and 3c of the ceiling surface 3a are configured with gently curved surfaces, and the outer edge portions 5c and 5d of the crown surface 5b of the piston 5 are also configured with gently curved surfaces, thereby increasing the compression stroke. When the piston 5 rises, as the piston 5 rises, air on the surface of the crown surface 5b of the piston 5 is pushed up by the crown surface 5b, forming an upward flow. On the gently curved surfaces 5c and 5d, there are ascending flows directed toward the OP ₁ side and the OP ₂ side, respectively. It is also possible to suppress the flow that compresses the surface 5b.

In addition, by forming the outermost edge portions 3e and 3f of the ceiling surface 3a and the outermost edge portions 5e and 5f of the piston 5 as rising inclined surfaces, the inner peripheral surface 4a of the cylinder liner 4 and the outermost By reducing the geometric volume formed between the outer edge portions 5e and 5f, compression in the outer edge region of the piston 5 during the compression stroke can be reduced, and the outer edge portions 3b and 3c of the ceiling surface 3a and A space surrounded by the outer edge portions 5c and 5d of the piston 5, a space surrounded by the intake side inclined surface 3d, the intake side inclined surfaces 5k and 5i and the flat portion 5g, the exhaust side inclined surface 3e and the exhaust side inclined surface 5l, It is possible to suppress the squish flow that jets out as a jet due to the compression of the space surrounded by 5j and the flat portion 5h and the space of the cavity 5a. can be reduced.

The configuration of the crown surface 5b of the piston 5 used in the above description will be described below.

6. Configuration of crown surface 5b of piston 5 The configuration of the crown surface 5b of the piston 5 will be described with reference to FIG. In addition, the following description is omitted about the part which overlaps with the above-mentioned description.

As shown in FIG. 7, the outermost edge portions 5e and 5f, which are rising inclined surfaces, are provided on the OP ₁ side and the OP ₂ side of the crown surface 5b of the piston 5. As shown in FIG. The outermost edge portions 5e and 5f gradually decrease in width in the radial direction toward the In side and the Ex side in the circumferential direction.

A portion of the crown surface 5b facing the intake port openings 6a and 6b forms an intake-side slope portion 5k that functions as a part of the squish flow generating portion. The intake-side inclined surface 5k is a portion of the ceiling surface 3a along the intake-side inclined surface 3d.

A portion of the crown surface 5b facing the exhaust port openings 7a and 7b also forms an exhaust-side slope portion 5l that functions as a part of the squish flow generating portion. The exhaust-side inclined surface 5l is a portion of the ceiling surface 3a along the exhaust-side inclined surface 3e. Therefore, the inclination angle of the exhaust-side slope portion 5l is looser (smaller) than the intake-side slope portion 5k.

A plane portion 5g is formed along a plane that is virtually orthogonal to the cylinder axis Ax _1a on the outer edge portion on the In side of the crown surface 5b. Similarly, a plane portion 5h is formed along a virtual plane perpendicular to the cylinder axis Ax1a on the Ex-side outer edge portion of the crown surface 5b.

Between the plane portion 5g and the cavity 5a and between the intake side slope portions 5k, an inter-valve plane portion 5i is formed along a plane virtually orthogonal to the cylinder axis Ax _1a . there is Similarly, between the flat portion 5h and the cavity 5a and sandwiched between the exhaust-side slope portions 5l, there is an inter-valve flat portion 5j along a plane virtually perpendicular to the cylinder axis Ax _1a . formed.

The inter-bulb flat portion 5i is continuous with the flat portion 5g without a step, and the inter-bulb flat portion 5j is continuous with the flat portion 5h without a step.

In this way, in the engine 1, by providing the inter-valve flat portions 5i and 5j on the crown surface 5b of the piston 5, compared to the bending from the inter-valve flat portion 5j to the flat portion 5h on the exhaust side, In the bending from the inter-valve flat portion 5i to the flat portion 5g, the inclination angle of the inclined surface on the intake side is large (severe), so the resistance of the airflow increases and the attenuation progresses.

Compared to the generation of squish flow (flow F ₃₀ shown in FIG. 9) and reverse squish flow (flow opposite to flow F ₃₀ in FIG. 9) at the intake side openings 6a and 6b, the exhaust side opening 7a , 7b (flow F ₃₁ in FIG. 9) and reverse squish flow (flow in the opposite direction to flow F ₃₁ in FIG. 9). As a result, in the engine 1, since it is possible to suppress an increase in combustion turbulence due to the squish flow and the reverse squish flow generated on the combustion chamber surface on the intake side, the wall surface is relatively cold compared to the combustion chamber surface on the exhaust side. It becomes possible to suppress the cooling loss on the combustion chamber surface on the intake side.

7. Tumble Flow in Combustion Chamber 10 A tumble flow generated by air taken into the combustion chamber 10 will be described with reference to FIG. FIG. 8 is a schematic diagram showing the flow of air in the combustion chamber 10. As shown in FIG.

As shown in FIG. 8, when the intake valve 11 is in the open state, the air F1 flowing through the intake port ₆ is directed toward the Lo side by the inclined surface 6e provided on the upstream side of the valve guide 13. The part is turned (F ₁₄ ). Note that the air F ₁₅ (F ₂ and F ₃ in FIG. 2) flowing on the Lo side of the intake port 6 is directed toward the Lo side under the influence of the inclined surface 6e, and in the region where the intake valve 11 is inserted, The flow is in a compressed state (F ₁₆ ).

The above [4. Configuration of intake port 6], when the air passage portions 6f and 6g are formed on both sides of the inclined surface 6e, a virtual line in the engine output shaft direction (OP ₁ -OP ₂ direction) The width of the passage 6f on the opposite side of Ax _1X is narrow, and the flow velocity of the air F ₁₄₀ passing through this is increased, and the gap between the valve seat 8 and the head portion 11a of the intake valve 11 enters the combustion chamber 10. and air is introduced (F ₁₇ ). The air flow F17 in FIG. ₈ corresponds to _F4 and F9 in FIG.

The flow of air introduced into the combustion chamber 10 flows between the outer edges 3b, 3c of the ceiling surface 3a of the cylinder head 3 shown in FIG. It is introduced into the area surrounded by the planes sandwiched between the two, and flows along the planes toward the OP ₁ side and the OP ₂ side and gradually toward the Lo side (F ₁₈ ). The air flow _F18 corresponds to _F5 and _F10 in FIG.

As shown in FIG. 2, the air flow F ₁₈ changes its direction (F ₆ and F ₁₁ in FIG. 2) by hitting the inner peripheral surface 4a of the cylinder liner 4, and has components facing each other ( _F19 ). The air flow _F19 corresponds to _F7 and _F12 in FIG.

Also, the air F16 flowing through the intake port 6 is introduced into the combustion chamber ₁₀ through the gap between the valve seat 8 and the head portion 11a of the intake valve 11 ( _F17 , _F22 ). Among them, the air F17 introduced toward the exhaust valve 12 on the exhaust side ₍ Ex side) is caused by the Coanda effect of the exhaust-side inclined surface 3e due to the inclination setting of the exhaust-side inclined surface 3e described with reference to FIG. is not strongly received, and the peeled state is not along the exhaust-side inclined surface 3e (F ₁₈ ).

As described above, the air F ₁₈ separated from the exhaust-side inclined surface 3e hits the inner peripheral surface 4a of the cylinder liner 4, changes its traveling direction radially inward, and moves toward the piston 5 (Lo side). (F ₁₉ ). Then, the air F ₁₉ travels along the bottom surface of the cavity 5a of the piston 5 with a gap left therebetween (F ₂₀ ), and then turns to the Up side (F ₂₁ ).

The air F17 introduced to the exhaust side ₍ Ex side) in this way constitutes a positive tumble flow that swirls slightly.

On the other hand, air F ₂₂ (corresponding to F ₈ and F ₁₃ in FIG. (F ₂₃ ). Part of the air _F23 that hits the crown surface 5b of the piston 5 travels along the intake-side slope portion 5k (see FIG. 7) with a gap therebetween, and turns upward ( _F24 , _F25 ).

The air F22 introduced to the side ( _In side) opposite to the Ex side in this manner forms a reverse tumble flow opposing the normal tumble flow.

In the engine 1 according to the present embodiment, by balancing the normal tumble flow and the reverse tumble flow, more specifically, by generating a normal tumble flow that swirls slightly in the combustion chamber 10, the strength of the normal tumble flow is increased. can be suppressed, turbulence in the combustion chamber can be reduced, and the air-fuel mixture can be stratified in the central portion of the combustion chamber 10 .

8. Setting of the Inclination Angles of the Intake-Side Inclined Surface 3d and the Exhaust-Side Inclined Surface 3e and Squish Flow The relationship between the setting of the inclination angles of the intake-side inclined surface 3d and the exhaust-side inclined surface 3e and the generated squish flow is shown in FIG. explain. FIG. 9 is a schematic diagram showing a squish flow generated between the ceiling surface 3a and the crown surface 5b of the piston 5 during the compression stroke.

As shown in FIG. 9, in the compression stroke, a squish flow is generated between the ceiling surface 3a and the crown surface 5b of the piston 5 as the piston 5 moves upward. Here, as described with reference to FIG. 3, the intake-side inclined surface 3d and the exhaust-side inclined surface 3e of the ceiling surface 3a satisfy the above-described relationship (Equation 1), and the portion facing the crown surface 5b of the piston 5 (Intake-side inclined surface 5k, exhaust-side inclined surface 5l) are provided along the intake-side inclined surface 3d and the exhaust-side inclined surface 3e.

Therefore, as shown in part B of FIG. 9, in the compression stroke, the intake-side inclined surface 3d of the ceiling surface 3a and the intake-side inclined surface 5k of the piston 5 approach each other, thereby generating a squish flow _F30 . be done. Similarly, as shown in part C of FIG. 9, the exhaust-side inclined surface 3e of the ceiling surface 3a and the exhaust-side inclined surface 5l of the piston 5 approach each other, thereby generating a _squish flow F31.

Here, when the squish flows F ₃₀ and F ₃₁ are represented by vector components in the Up-Lo direction and the In-Ex direction, the squish flow F ₃₀ is a composite vector of the component F _30UL and the component F _30IE . Also, the squish flow _F31 is a composite vector of the component _F31UL and the component _F31IE .

In this embodiment, the ceiling surface 3a is formed so as to satisfy the above relationship (Equation 1), so the squish flows F ₃₀ and F ₃₁ satisfy the following relationship.

F _31IE >F _30IE (Equation 2)
By satisfying the above relationship (Equation 2), in the engine 1, the normal tumble flow can be separated from the exhaust-side portion of the inner peripheral surface 4a of the cylinder liner 4 during the compression stroke. and the configuration can be reduced.

The horizontal component _{F31IE of the stronger squish flow F31 directed from the exhaust side to the intake side than the horizontal component F30IE of} the squish flow _F30 directed from the intake side to the exhaust side causes the positive tumble flow directed from the intake side to the exhaust side. It is possible to suppress the flow.

9. Configuration of Fuel Injection Valve 15 and Fuel Injection Timing The configuration of the fuel injection valve 15 and fuel injection timing will be described with reference to FIGS. 10 and 11. FIG. FIG. 10 is a schematic cross-sectional view showing the configuration of part of the fuel injection valve 15 (the head portion and its vicinity), and FIG. 11 is a timing chart showing the fuel injection period.

As shown in FIG. 10, the fuel injection valve 15 includes an outer cylindrical portion 151 having a cylindrical shaft arranged along the central axis Ax ₁₅ , and a portion of the fuel injection valve 15 that is accommodated inside the cylindrical shaft 151 and protrudes from the Lo side. and a needle valve portion 152 . A fuel passage 15 a is formed between the outer cylindrical portion 151 and the needle valve portion 152 .

In addition, when the needle valve portion 152 is pushed down to the Lo side and opened, a fuel passage 15b that is continuous with the fuel passage 15a is also formed.

The fuel F ₄₀ in the fuel passage 15a passes through the fuel passage 15b (F ₄₁ ) and is injected to the Lo side (F ₄₂ ) when the needle valve portion 152 is pushed down to open the valve. Here, the injected fuel F ₄₂ spreads annularly (doughnut-shaped) around the central axis Ax ₁₅ of the fuel injection valve 15 .

As shown in FIG. 11, in the engine 1 according to this embodiment, the fuel injection timing is set in the latter half of the compression stroke. Specifically, the fuel injection period _TFI is set to _a period from timing t1 to timing t2 in the latter _half of the compression stroke.

Note that, as shown in FIG. 11, in the engine 1 according to the present embodiment, fuel injection is not performed continuously once, but intermittently multiple times (fuel injections FI ₁ , FI ₂ , FI ₃ ). In this embodiment, three fuel injections are intermittently performed.

In the engine 1 according to this embodiment, the speed of the injected fuel can be suppressed by intermittently performing the fuel injection in a plurality of times. That is, by intermittently performing a plurality of fuel injections, the speed of the injected fuel as a whole is increased by subsequent fuel injections FI ₂ and FI ₃ compared to the case of continuously injecting fuel. can be suppressed.

Note that the fuel injection may be performed intermittently divided into two times, or may be performed intermittently divided into four times or more.

10. Injected fuel I _F for cavity 5a
The form of the injected fuel _IF with respect to the cavity 5a will be described with reference to FIG. FIG. 12 is a schematic diagram showing the state of the injected fuel _IF with respect to the cavity 5a.

The fuel (injected fuel I _F ) intermittently injected three times as described above is accommodated inside the cavity 5 a of the piston 5 . 12, an air layer _LA is formed between the injected fuel _IF and the bottom surface of the cavity 5a on the crown surface 5b of the piston 5. As shown in FIG.

As described above, in the engine 1 according to the present embodiment, the injected fuel IF is _combusted before it contacts the crown surface 5b of the piston 5, so cooling loss can be reduced.

[Embodiment 2]
A configuration of a direct injection engine according to Embodiment 2 will be described with reference to FIG. 13 . FIG. 13 is a diagram corresponding to FIG. 2 of the first embodiment, and is a schematic plan view showing the configuration of the cylinder 19a in the direct injection engine.

Note that the direct injection engine 1 according to the present embodiment differs from the direct injection engine 1 according to the first embodiment described above in the configuration of the intake port 20, except that the direct injection engine 1 according to the first embodiment. has the same configuration as Therefore, only the configuration of the intake port 20 will be described below.

As shown in FIG. 13 , the intake port 20 is constructed by combining an independent intake port 201 and an independent intake port 202 . In the direct injection engine according to this embodiment, the configuration of the intake port 20 does not include a collective intake port.

The independent intake port 201 is connected to the combustion chamber 10 via an intake port opening 20a, and the independent intake port 202 is connected to the combustion chamber 10 via an intake port opening 20b. The intake port opening 20a is provided on the OP ₁ side with respect to the virtual line Ax _19X , and the intake port opening 20b is provided on the OP ₂ side with respect to the virtual line Ax _19X .

Therefore, the independent intake port 201 is provided on the OP ₁ side with respect to the virtual line Ax _19X , and the independent intake port 202 is provided on the OP ₂ side with respect to the virtual line Ax _19X .

As shown in FIG. 13, also in this embodiment, an imaginary line Ax _19X is drawn from the cylinder axis Ax _19a in the intake/exhaust direction (In-Ex direction). At this time, the independent intake port 201 is provided with its central axis Ax ₂₀₁ inclined at an angle θ ₂₀₁ with respect to the imaginary line Ax _19X . In other words, in this embodiment as well, the center axis Ax ₂₀₁ of the independent intake port 201 is directed from the In side toward the intake port opening 20a side and toward the outer side (OP1 _side ) in the cross-sectional radial direction of the cylinder 19a. It is actively (intentionally) configured to

On the other hand, the independent intake port 202 is provided with its central axis Ax ₂₀₂ inclined at an angle θ ₂₀₂ with respect to the imaginary line Ax _19X . In other words, in this embodiment as well, the center axis Ax ₂₀₂ of the independent intake port 202 is directed from the In side toward the intake port opening 20b side toward the outside (OP2 _side ) in the cross-sectional radial direction of the cylinder 19a. It is actively (intentionally) configured to

In the direct injection engine having the independent intake ports 201 and 202 arranged as described above, when the intake valve 11 is in the open state, the arrows F ₄ to F ₁₃ and F ₅₁ to F ₅₃ in FIG. air flow is formed. That is, the air _F51 that has flowed through the independent intake ports 201 and 202 flows along the directions of the independent intake ports 201 and 202 ( _F52 , _F53 ). That is, the air F52 of the independent intake port ₂₀₁ flows along the central axis _Ax201 toward the intake port opening 20a. Similarly, air F ₅₃ in independent intake port 202 flows along central axis Ax ₂₀₂ toward intake port opening 20b.

Part of the air F ₅₂ that has reached the intake port opening 20a is led to the exhaust side (Ex side) of the combustion chamber 10 along the upper surface of the head portion 11a of the intake valve 11 (F ₄ ), Part of it is led out to the opposite side (In side) (F ₈ ). Similarly, the air F ₅₃ that has reached the intake port opening 20b is partly guided to the exhaust side (Ex side) of the combustion chamber 10 along the upper surface of the head portion 11a of the intake valve 11 (F ₉ ), part of which is led to the opposite side (In side) (F ₁₃ ).

The flow of air introduced into the combustion chamber 10 is the same as in the first embodiment.

The direct-injection engine having the configuration described above can also achieve the same effects as the direct-injection engine 1 according to the first embodiment.

[Modification]
Although the two independent intake ports 61, 62, 201, 202 are connected to the cylinders 1a, 19a in the first and second embodiments, the present invention is not limited to this. For example, a form in which one independent exhaust port is connected to a cylinder, or a form in which three or more independent intake ports are connected to a cylinder, etc. can be adopted. Similarly, as for the exhaust port, it is also possible to employ a form in which one is connected to the cylinder, or a form in which three or more are connected.

Further, in the above-described first and second embodiments, no specific examples of the type of the engine 1 were specifically mentioned, but various types can be adopted. For example, it can be applied to a single-cylinder engine or a multi-cylinder engine having two or more cylinders. In addition, regarding the type of engine, not only an in-line type engine but also a V-type, W-type, or horizontally opposed type engine can be adopted.

Further, in the first and second embodiments, the configuration in which the cylinder liner 4 is fitted into the cylinder block 2 is taken as an example, but the present invention is not limited to this. For example, a form in which a sprayed layer is provided on the inner surface of a bore formed in the cylinder block may be adopted.

1 Direct injection engine 1a, 19a Cylinder 3 Cylinder head 3a Ceiling surface 3d Intake-side inclined surface 3e Exhaust-side inclined surface 4 Cylinder liner 4a Inner wall surface 5 Piston 5a Cavity 5k Intake-side inclined surface 5l Exhaust-side inclined surface 6, 20 Intake port 6a Intake side opening (first intake side opening)
6b intake side opening (second intake side opening)
6e Inclined surface 7 Exhaust port 7a Exhaust side opening (first exhaust side opening)
7b exhaust side opening (second exhaust side opening)
REFERENCE SIGNS LIST 10 combustion chamber 11 intake valve 12 exhaust valve 61, 201 independent intake port (first independent intake port)
62, 202 independent intake port (second independent intake port)
71 independent exhaust port (first independent exhaust port)
72 independent exhaust port (second independent exhaust port)

Claims (8)

A direct injection engine having a cylinder forming a combustion chamber,
a ceiling surface that is composed of a pent roof-shaped surface having an intake side inclined surface that is inclined from the top toward the intake side and an exhaust side inclined surface that is inclined toward the exhaust side, and constitutes the ceiling of the combustion chamber;
The cylinder slides in the cylinder axial direction, and the crown surface constitutes the lower surface of the combustion chamber in the cylinder axial direction. a piston having a recessed cavity;
an intake port having an intake-side opening opened in the intake-side inclined surface, the intake port being continuous with the combustion chamber at the intake-side opening;
an exhaust port having an exhaust-side opening opened in the exhaust-side inclined surface and connected to the combustion chamber at the exhaust-side opening;
a fuel injection valve provided to face the combustion chamber from the ceiling;
with
When the intake port is viewed in plan from the axial direction of the cylinder, a predetermined area on the upstream side of the intake-side opening in the air flow direction passes through the central axis of the cylinder and extends in the intake and exhaust direction. It is arranged so as to face radially outward of the cylinder with respect to the axis along the
When a virtual plane perpendicular to the cylinder axis is assumed, the inclination angle formed by the exhaust-side inclined surface with respect to the virtual plane is smaller than the inclination angle formed by the intake-side inclined surface with respect to the virtual plane. and
fuel is injected from the fuel injection valve into the combustion chamber in the latter half of the compression stroke in a predetermined engine load region;
The crown surface of the piston includes a peripheral edge of the cavity, an intake-side inclined surface facing the intake-side inclined surface and inclined with respect to the imaginary plane, and an intake-side inclined surface facing the exhaust-side inclined surface and facing the imaginary and an exhaust-side slope portion inclined with respect to the plane,
an inclination angle formed by the exhaust side slope portion with respect to the virtual plane is smaller than an inclination angle formed by the intake side slope portion with respect to the virtual plane;
direct injection engine. A direct injection engine according to claim 1 ,
the intake-side inclined surface on the crown surface of the piston is along the intake-side inclined surface on the ceiling surface;
The exhaust-side inclined surface of the crown surface of the piston is along the exhaust-side inclined surface of the ceiling surface,
direct injection engine. A direct injection engine according to claim 1 or claim 2 ,
The intake port is
a first independent intake port continuous with the combustion chamber at a first intake-side opening opened in the intake-side inclined surface;
a second independent intake port connected to the combustion chamber at a second intake-side opening opened with a gap from the first intake-side opening with respect to the intake-side inclined surface;
has
When the first independent intake port and the second independent intake port are viewed from the cylinder axis direction,
A central axis of the first independent intake port is such that a region extending from an upstream side in an air flow direction to the first intake side opening is positioned relative to an axis passing through the central axis of the cylinder and extending in the intake and exhaust direction. It is arranged so as to face one outside in the radial direction,
The central axis of the second independent intake port is such that a region extending from the upstream side in the air flow direction to the second intake side opening is positioned relative to the axis passing through the central axis of the cylinder and extending in the intake and exhaust direction. arranged to face the other outside in the radial direction,
direct injection engine. A direct injection engine having a cylinder forming a combustion chamber,
a ceiling surface that is composed of a pent roof-shaped surface having an intake side inclined surface that is inclined from the top toward the intake side and an exhaust side inclined surface that is inclined toward the exhaust side, and constitutes the ceiling of the combustion chamber;
The cylinder slides in the cylinder axial direction, and the crown surface constitutes the lower surface of the combustion chamber in the cylinder axial direction. a piston having a recessed cavity;
an intake port having an intake-side opening opened in the intake-side inclined surface, the intake port being continuous with the combustion chamber at the intake-side opening;
an exhaust port having an exhaust-side opening opened in the exhaust-side inclined surface and connected to the combustion chamber at the exhaust-side opening;
a fuel injection valve provided to face the combustion chamber from the ceiling;
with
When the intake port is viewed in plan from the axial direction of the cylinder, a predetermined area on the upstream side of the intake-side opening in the air flow direction passes through the central axis of the cylinder and extends in the intake and exhaust direction. It is arranged so as to face radially outward of the cylinder with respect to the axis along the
When a virtual plane perpendicular to the cylinder axis is assumed, the inclination angle formed by the exhaust-side inclined surface with respect to the virtual plane is smaller than the inclination angle formed by the intake-side inclined surface with respect to the virtual plane. and
fuel is injected from the fuel injection valve into the combustion chamber in the latter half of the compression stroke in a predetermined engine load region;
The intake port is
a first independent intake port continuous with the combustion chamber at a first intake-side opening opened in the intake-side inclined surface;
a second independent intake port connected to the combustion chamber at a second intake-side opening opened with a gap from the first intake-side opening with respect to the intake-side inclined surface;
has
When the first independent intake port and the second independent intake port are viewed from the cylinder axis direction,
A central axis of the first independent intake port is such that a region extending from an upstream side in an air flow direction to the first intake side opening is positioned relative to an axis passing through the central axis of the cylinder and extending in the intake and exhaust direction. It is arranged so as to face one outside in the radial direction,
The central axis of the second independent intake port is such that a region extending from the upstream side in the air flow direction to the second intake side opening is positioned relative to the axis passing through the central axis of the cylinder and extending in the intake and exhaust direction. It is arranged so as to face the other outside in the radial direction,
The exhaust port is
a first independent exhaust port connected to the combustion chamber at a first exhaust-side opening opened in the exhaust-side inclined surface;
a second independent exhaust port connected to the combustion chamber at a second exhaust-side opening opened with a gap from the first exhaust-side opening with respect to the exhaust-side inclined surface;
has
the crown surface of the piston,
In the region between the portion below the first intake side opening in the cylinder axial direction and the portion below the second intake side opening in the cylinder axial direction, A planar portion between the intake valves along,
In the region between the portion below the first exhaust side opening in the cylinder axial direction and the portion below the second exhaust side opening in the cylinder axial direction, A flat portion between the exhaust valves along,
having
direct injection engine. A direct injection engine according to claim 4 ,
The crown surface of the piston includes a peripheral edge of the cavity, an intake-side inclined surface facing the intake-side inclined surface and inclined with respect to the imaginary plane, and an intake-side inclined surface facing the exhaust-side inclined surface and facing the imaginary and an exhaust-side slope portion inclined with respect to the plane,
an inclination angle formed by the exhaust side slope portion with respect to the virtual plane is smaller than an inclination angle formed by the intake side slope portion with respect to the virtual plane;
direct injection engine. The direct injection engine according to any one of claims 1 to 5 ,
From the fuel injection valve, fuel is intermittently injected multiple times into the combustion chamber in the latter half of the compression stroke in the predetermined engine load region.
direct injection engine. The direct injection engine according to any one of claims 1 to 6 ,
further comprising an intake valve for opening and closing the intake side opening;
The intake valve has a shaft portion inserted through the upper wall of the intake port and inserted into the intake port, and an umbrella portion provided at a tip portion of the shaft portion on the combustion chamber side,
The inner surface of the upper wall of the intake port is inclined such that a portion adjacent to the upstream side in the air flow direction of the portion through which the shaft portion of the intake valve is inserted is oriented toward the intake side opening. Consists of faces,
direct injection engine. A direct injection engine according to claim 7 ,
A portion of the intake port formed by the inclined surface of the inner surface is connected to a portion on the upstream side in the air flow direction of the portion by a smooth curved surface.
direct injection engine.

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