JP6798460B2 - Internal combustion engine - Google Patents

Description

The present invention relates to an internal combustion engine, and more particularly to an internal combustion engine having a single intake port and a single exhaust port.

As a conventional technique for strengthening a vortex in a cylinder in an internal combustion engine, for example, a fuel injection device disclosed in Patent Document 1 is known. In the engine disclosed in Patent Document 1, the air blast injector includes a first injector that injects fuel and a second injector that injects pressurized air. Further, the air blast injector includes an injection hole forming member in which a fuel injection hole for injecting air mixed fuel into the cylinder and an air injection hole for injecting only pressurized air into the cylinder are formed.

The fuel injection hole injects the air mixed fuel toward the upper side of the cylinder so as to strengthen the tumble flow. The air injection hole injects the pressurized air above the injection direction of the fuel injection hole so as to inject the pressurized air in the direction of strengthening the tumble flow and toward the outer peripheral side of the tumble flow. As a result, an air curtain is formed on the outer periphery of the tumble flow, and the tumble flow formed in the cylinder is strengthened by the air mixed fuel injected from the fuel injection hole.

Japanese Unexamined Patent Publication No. 2011-99353

By the way, in an internal combustion engine, it is required to improve thermal efficiency and improve fuel efficiency by increasing the combustion speed of initial combustion from ignition. In an internal combustion engine, there are a swirl flow of a flow along the inner wall of a cylinder and a tumble flow of a flow rotating in the stroke direction of the piston. The swirl flow contributes little to the increase in combustion rate during initial combustion from ignition, and the tumble flow contributes to the increase in combustion rate during initial combustion. However, in a two-valve internal combustion engine with a single intake port and a single exhaust port, the intake and exhaust ports are located eccentrically from the center of the cylinder bore at the top of the combustion chamber, respectively. In the cylinder bore, it is inevitable that the swirl flow formed along the bore wall becomes dominant.

Incidentally, the fuel injection device disclosed in Patent Document 1 strengthens the tumble flow by injecting pressurized air, but merely avoids cylinder wetness due to the air mixed fuel injected from the fuel injection hole.

The present invention has been made in view of the above problems, and an object of the present invention is to enhance the tumble flow in a two-valve internal combustion engine having a single intake port and a single exhaust port. It is in the provision of an internal combustion engine.

In order to solve the above problems, the present invention presents a cylinder bore in which a reciprocating piston is housed, a combustion chamber formed in the cylinder bore by the piston, and a single chamber arranged with respect to the combustion chamber. It includes an intake port and a single exhaust port, an intake valve that opens and closes the intake port, and an exhaust valve that opens and closes the exhaust port, and a swirl flow is formed in the combustion chamber by intake air from the intake port in the intake stroke. In the internal combustion engine, a tumble flow is formed in the combustion chamber by being provided between the intake port and the exhaust port and injecting compressed air toward the bore wall in the combustion chamber in the intake stroke. A compressed air injector is provided, and the direction of injection of compressed air injected from the compressed air injector toward the bore wall in a plan view of the combustion chamber passes through the injection port of the compressed air injector and is directed to the intake port. Included in the planoscopic fan-like range between the virtual line along the flow of intake air flowing through the connected intake passage and the virtual line passing through the nozzle of the compressed air injector and passing through the center of the intake port. It is characterized in that the compressed air injected by the compressed air injector interferes with the swirl flow and the swirl flow is drawn into the tumble flow.

In the present invention, the air-fuel mixture is taken into the combustion chamber from the intake port in the intake stroke in which the piston descends, so that a swirl flow is generated in the combustion chamber. The compressed air injector injects compressed air in the intake stroke in which the piston descends. The jet of compressed air forms a tumble flow in the combustion chamber, and the tumble flow intersects and interferes with the swirl flow, so that the swirl flow is drawn into the tumble flow. Therefore, the ratio of the fluid energy due to the tumble flow to the fluid energy in the combustion chamber is higher than the ratio of the fluid energy due to the swirl flow. The tumble flow in the combustion chamber can be strengthened.

Further, it is possible to interfere with swirl the compressed air at a relatively close position the air intake port, it is possible to convert the swirl flow efficiently to tumble flow.

Further, in the internal combustion engine, the compressed air injector may be configured to inject compressed air when the piston descends from the top dead center to the midpoint between the bottom dead center in the intake stroke.
In this case, by injecting compressed air when the piston descends from the top dead center to the midpoint between the bottom dead center in the intake stroke, a tumble flow suitable for increasing the combustion speed at the time of initial combustion is formed. Can be done.

Further, in the internal combustion engine, the compressed air injector may be configured to include a plurality of nozzles for injecting compressed air in a plurality of directions in the circumferential direction of the combustion chamber.
In this case, since the compressed air intersects the swirl flow at a plurality of points, it becomes easier to draw the swirl flow into the tumble flow.

According to the present invention, in a two-valve internal combustion engine having a single intake port and a single exhaust port, it is possible to provide an internal combustion engine capable of enhancing the tumble flow.

It is a front sectional view which shows the outline of the engine which concerns on 1st Embodiment. It is a side sectional view which shows the outline of the engine which concerns on 1st Embodiment. It is the schematic plan view of the engine which concerns on 1st Embodiment. It is the schematic perspective view explaining the drawing of a swirl flow into a tumble flow. It is a schematic front view explaining the pulling of a swirl flow into a tumble flow. It is a figure which shows the injection control of compressed air. (A) It is a figure which shows the ratio of a swirl flow and a tumble flow, and (b) is a figure explaining the improvement of thermal efficiency of this embodiment. It is the schematic plan view of the engine which concerns on the modification of 1st Embodiment. It is the schematic plan view of the engine which concerns on 2nd Embodiment.

(First Embodiment)
Hereinafter, the internal combustion engine according to the first embodiment will be described with reference to the drawings. The internal combustion engine of the present embodiment is a spark-ignition type gas engine (hereinafter, simply referred to as "engine") that uses natural gas as fuel, and has a single intake port (intake valve) and a single intake valve in the combustion chamber. It is a two-valve engine equipped with an exhaust port (exhaust valve).

As shown in FIGS. 1 and 2, the engine 10 includes a cylinder block 11 and a cylinder head 12 joined to the upper portion of the cylinder block 11. The cylinder block 11 is provided with a cylinder bore 13 formed by a bore wall 11A, and a piston 14 that reciprocates is housed in the cylinder bore 13. The piston 14 and the cylinder block 11 and the cylinder head 12 form a combustion chamber 15 in the cylinder bore 13. The piston 14 is connected to a crankshaft (not shown) via a connecting rod (not shown). The piston 14 reciprocates between top dead center (TDC) and bottom dead center (BCD) in a series of steps of intake, compression, combustion / expansion, and exhaust.

The cylinder head 12 is provided with an intake port 16 and an exhaust port 17. The air-fuel mixture (intake) containing the vaporized fuel is introduced into the combustion chamber 15 from the intake port 16 connected to the intake passage. The combustion gas (exhaust) generated by the combustion of the air-fuel mixture is discharged from the combustion chamber 15 to the exhaust pipe (not shown) through the exhaust port 17. The intake port 16 is provided with an intake valve 18, and the intake valve 18 opens and closes the intake port 16. The exhaust port 17 is provided with an exhaust valve 19, and the exhaust valve 19 opens and closes the exhaust port 17. In the present embodiment, the inner diameter of the intake port 16 is set to be slightly larger than the inner diameter of the exhaust port 17 in order to efficiently take the intake air into the combustion chamber 15.

As shown in FIG. 3, in the present embodiment, the intake port 16 and the exhaust port 17 arranged in the upper part of the combustion chamber 15 are provided at positions eccentric from the center P of the cylinder bore 13 in the plan view of the combustion chamber 15. ing. The flow direction of the intake air flowing through the intake passage connected to the intake port 16 and the flow direction of the exhaust gas flowing through the exhaust passage connected to the exhaust port 17 are parallel and opposite. In the engine 10 of the present embodiment, since the intake port 16 is provided at a position eccentric from the center P of the cylinder bore 13, the intake air introduced into the combustion chamber 15 flows in one direction along the bore wall 11A and flows in one direction to the combustion chamber. A swirl flow (transverse vortex) S is inevitably formed within 15.

As shown in FIG. 2, the cylinder head 12 is provided with a spark plug 20 and a compressed air injector 21. The spark plug 20 is for igniting the air-fuel mixture in the combustion chamber 15, and is a known spark plug. The compressed air injector 21 is for injecting compressed air into the combustion chamber 15 to form a tumble flow (longitudinal vortex flow) T in the combustion chamber 15 as shown in FIG. As shown in FIG. 3, in the present embodiment, the compressed air injector 21 is located on the line of the virtual line L1 passing between the intake port 16 and the exhaust port 17. The virtual line L1 is a line passing through the center P of the cylinder bore 13. In FIGS. 3 and 4, the spark plug 20 is not shown. The virtual line L2 is a line passing through the center Q of the intake port 16.

The compressed air injector 21 includes an injector main body 22 held by the cylinder head 12. A nozzle 23 is provided at the tip of the injector main body 22. The injection port 23 faces the combustion chamber 15 and enables the injection of compressed air into the combustion chamber 15. In the present embodiment, the injection direction of the compressed air injected from the injection port 23 is the direction along the virtual line L1 in the plan view shown in FIG. 3, that is, the intake air flowing in the intake passage connected to the intake port 16. It is a direction along the flow direction and is a direction from between the intake port 16 and the exhaust port 17 toward the bore wall 11A near the spark plug 20.

The injection direction of the compressed air in the plan view of the combustion chamber 15 is a virtual line L1 (extension of the virtual line L1) that passes through the injection port 23 and is along the flow direction of the intake air flowing through the intake passage connected to the intake port 16. The direction) and the range up to the virtual line L2 (the extending direction of the virtual line L2) passing through the injection port 23 and the center Q of the intake port 16 (referred to as “injection preferable range”). That is, the optimum injection range is the direction parallel to the intake air (extending direction of the virtual line L1) between the intake port 16 and the exhaust port 17 and the direction orthogonal to the intake air of the intake port 16 and the intake port 16 It is a plane-viewing fan-shaped range between the direction passing through the center Q (the extending direction of the virtual line L2). By injecting compressed air into the combustion chamber 15 within a suitable injection range from the virtual line L1 to the virtual line L2, the swirl flow S formed when the intake air is introduced into the combustion chamber 15 is tumble flow T. Can be efficiently converted to.

The injection direction of the compressed air injector 21 in the side view shown in FIG. 2 is a direction inclined with respect to the central P-axis of the cylinder bore 13, and intersects a specific position on the bore wall 11A. Specifically, the specific position on the bore wall 11A is a position at an intermediate height between the top dead center and the bottom dead center of the piston 14 (hereinafter referred to as "intermediate point").

The compressed air injector 21 is connected to the air compressor 24 via a pipe 25. The air compressor 24 sucks air, compresses it, and supplies compressed air to the compressed air injector 21 through the pipe 25. The compressed air injector 21 is connected to an ECU (Engine Control Unit) (not shown), and injects compressed air based on a command from the ECU. In the present embodiment, when the piston 14 reaches the midpoint (1/2 position) between the top dead center and the bottom dead center in the process of displacement from the top dead center to the bottom dead center, the compressed air injector 21 Inject compressed air. The ECU controls the compressed air injector 21 and also controls the air compressor 24.

Next, each process of the engine 10 of the present embodiment will be described. Immediately after the exhaust stroke of the engine 10 is completed, the piston 14 is located at the top dead center. In the intake stroke after the exhaust stroke, the intake valve 18 opens the intake port 16 and the piston 14 descends. When the intake valve 18 opens the intake port 16, the intake port 16 and the combustion chamber 15 are communicated with each other, and the intake air is introduced from the intake port 16 to the combustion chamber 15. The intake air introduced into the combustion chamber 15 hits the bore wall 11A of the cylinder bore 13, flows in one direction along the bore wall 11A, and swirls a swirl flow (transverse vortex) S centered on the center P of the cylinder bore 13. Form.

When the piston 14 reaches the midpoint (1/2 position) between the top dead center and the bottom dead center, the compressed air injector 21 injects compressed air. As shown in FIGS. 4 and 5, the compressed air injected from the compressed air injector 21 hits the bore wall 11A toward the piston 14 and forms a flow of air hitting the top surface of the piston 14. The air flow that hits the top surface of the piston 14 hits the bore wall 11A again and heads for the cylinder head 12. That is, a tumble flow T that swirls in a direction orthogonal to the circumferential direction of the bore wall 11A is formed.

The compressed air injected from the compressed air injector 21 forms a tumble flow T in the combustion chamber 15, but intersects and interferes with the swirl flow S. The compressed air forming the tumble flow T interferes with the swirl flow S, so that the swirl flow S is drawn into the tumble flow T. Since the injection direction of the compressed air is included in the injection suitable range in which the swirl flow S from the virtual line L1 to the virtual line L2 can be efficiently converted into the tumble flow T, it is upstream of the swirl flow S. The tumble flow T interferes with the side, and the formation of the swirl flow S is hindered by the tumble flow T. In FIGS. 3 to 5, the swirl flow S before interfering with the tumble flow T is shown by a solid line, and the swirl flow S existing after the interference with the tumble flow T is shown by a dotted line.

In this embodiment, as shown in FIG. 6, compressed air is injected until the piston 14 reaches bottom dead center. Therefore, the compressed air forming the tumble flow T reduces the ratio of the fluid energy due to the swirl flow S to the fluid energy of the intake air in the combustion chamber 15 and increases the ratio of the fluid energy due to the tumble flow T. Therefore, the tumble flow T is dominant in the combustion chamber 15.

As shown in FIG. 7A, in the present embodiment configured to draw the swirl flow S into the tumble flow T by injecting compressed air, there is a comparative example of a two-valve engine that does not inject compressed air. By comparison, the tumble style T is dominant.

In the state where the tumble flow T is dominant in the combustion chamber 15, when the piston 14 rises in the compression stroke and approaches the top dead center, the tumble flow T in the combustion chamber 15 is eliminated and innumerable small vortices are formed. Will be done. That is, the combustion chamber 15 is dominated by turbulent energy that accelerates combustion by eliminating the tumble flow T. In the combustion / expansion stroke, when spark ignition is performed by the spark plug 20 while the combustion chamber 15 is dominated by turbulent energy, the air-fuel mixture in the combustion chamber 15 rapidly diffuses combustion. That is, the combustion rate in the initial combustion from ignition in the combustion / expansion stroke increases.

As shown in FIG. 7B, in the present embodiment configured to draw the swirl flow S into the tumble flow T by injecting compressed air, there is a comparative example of a two-valve engine that does not inject compressed air. By comparison, thermal efficiency is improved. The swirl ratio shown in FIG. 7B is the ratio of the flow velocity of the swirl flow S to the engine rotation speed, and the tumble ratio is the number of times the tumble flow T rotates in the combustion chamber 15 while the piston 14 makes one round trip. is there

When the combustion / expansion stroke is completed, the exhaust stroke is started. In the exhaust stroke, the exhaust valve 19 opens the exhaust port 17 and the piston 14 rises. As the piston 14 rises, the combustion gas formed by the combustion of the air-fuel mixture in the combustion chamber 15 is introduced into the exhaust port 17 as exhaust gas. The combustion gas introduced into the exhaust port 17 is discharged through an exhaust pipe (not shown).

The engine 10 according to the present embodiment has the following effects.
(1) A swirl flow S is generated in the combustion chamber 15 by being sucked into the combustion chamber 15 from the intake port 16 in the intake stroke in which the piston 14 descends. The compressed air injector 21 injects compressed air in the intake stroke in which the piston 14 descends. The tumble flow T is formed in the combustion chamber 15 by the injection of compressed air, and the tumble flow T intersects and interferes with the swirl flow S, so that the swirl flow S is drawn into the tumble flow T. Therefore, the ratio of the fluid energy due to the tumble flow T to the fluid energy in the combustion chamber 15 is higher than the ratio of the fluid energy due to the swirl flow S. The tumble flow in the combustion chamber 15 can be strengthened. When the tumble flow T becomes dominant in the combustion chamber 15, the combustion speed at the time of initial combustion increases and the thermal efficiency improves, so that fuel efficiency can be improved.

(2) The injection direction of the compressed air injected from the compressed air injector 21 is a direction parallel to the intake air between the intake port 16 and the exhaust port 17 (extending direction of the virtual line L1) and the intake port 16 It is included in a fan-shaped range in a plan view between the direction perpendicular to the intake air and the direction passing through the center Q of the intake port 16 (the extending direction of the virtual line L2). The compressed air forming the tumble flow T at a position relatively close to the intake port 16 can interfere with the swirl flow S, and the swirl flow S can be efficiently drawn into the tumble flow T.

(3) Since the injection direction of the compressed air injected by the compressed air injector 21 is parallel to the intake air at the intake port 16, the compressed air does not interfere with the introduction of the intake air from the intake port 16 to the combustion chamber 15, and the swirl flow S. Can be efficiently drawn into the tumble flow T.

(4) When the piston 14 descends from the top dead center to the midpoint between the bottom dead centers in the intake stroke, the compressed air injector 21 injects compressed air. By injecting compressed air when the piston 14 descends from the top dead center to the midpoint between the bottom dead center in the intake stroke, it is possible to form a tumble flow T suitable for increasing the combustion speed at the time of initial combustion. it can. Further, since the injection of compressed air by the compressed air injector 21 is continued until the piston 14 reaches the bottom dead center in the intake stroke, the ratio of the tumble flow T can be sufficiently increased.

(Modification example)
A modified example of the first embodiment will be described. In the present embodiment, the compressed air injector 21 is oriented so that the injection direction of the compressed air injector 21 is parallel to the direction in which the intake air of the intake port 16 flows in a plan view and coincides with the virtual line L1. Was placed. As for the injection direction of the compressed air injector 21, for example, as shown in FIG. 8, the compressed air injector 21 provided with the injection port 23 in which the injection direction faces the intake port 16 side may be arranged. This modification has the same effect as that of the first embodiment.

(Second Embodiment)
Next, the engine according to the second embodiment will be described. The present embodiment is different from the first embodiment in that the compressed air injector includes a plurality of nozzles, and other configurations are the same as those of the first embodiment. In the present embodiment, for the same configuration as that of the first embodiment, the description of the first embodiment is incorporated and a common reference numeral is used.

In the engine 30 shown in FIG. 9, a plurality of injection ports 33, 34, and 35 are provided at the tip of the injector main body 32 of the compressed air injector 31. Specifically, the tip of the injector main body 32 includes three nozzles, a first nozzle 33, a second nozzle 34, and a third nozzle 35. The first injection port 33 has an injection direction parallel to the intake air of the intake port 16 in a plan view. The second injection port 34 has an injection direction forming an angle of 30 ° with respect to the injection direction of the first injection port 33 on the intake port side. The third injection port 35 has an injection direction forming an angle of 30 ° toward the intake port side with respect to the injection direction of the second injection port 34. The injection directions of the first nozzle 33 to the third nozzle 35 all intersect the intermediate point between the top dead center and the bottom dead center of the piston 14. The pore diameters of the first nozzle 33, the second nozzle 34, and the third nozzle 35 are the same.

In this embodiment, the same effect as that of the first embodiment is exhibited. Further, since the compressed air forming the tumble flow T is injected from the plurality of nozzles 33 to 35 within the range in which the swirl flow S can be efficiently drawn into the tumble flow T, the compressed air is used to tumble the swirl flow S. It can be efficiently drawn into T.

The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the gist of the invention. For example, the present invention may be modified as follows.

○ In the above embodiment, the injection direction of the compressed air injector is in the range (angle) from the direction parallel to the intake air of the intake port to the direction toward the center of the intake port with reference to the center of the cylinder bore. This is not the case. For example, the injection direction of the compressed air injector may be a direction from a direction parallel to the intake air of the intake port toward the exhaust port side with reference to the center of the cylinder bore. That is, the injection direction of the compressed air injector may be included in the injection suitable range in which the swirl flow can be efficiently drawn into the tumble flow. In this case, the pulling of the swirl flow into the tumble flow is weaker than that of the above embodiment, but the proportion of the tumble flow can be increased.
○ In the above embodiment, the compressed air injector is provided on the cylinder head so that the axial direction of the compressed air injector is inclined with respect to the central axis of the cylinder bore, but this is not the case. For example, the compressed air injector may be provided in the cylinder head so that the axial direction of the compressed air injector coincides with the central axis of the cylinder bore.
○ In the above embodiment, an air compressor is used as a pressure source for compressed air, but a compressed air cylinder may be used instead of the air compressor. When a compressed air cylinder is used, the power loss of the engine can be reduced as compared with the case where an air compressor is used.
○ In the second embodiment, the pore diameters of the plurality of nozzles are the same, but the pore diameters may be different from each other. The number of nozzles is not limited to three, and for example, two nozzles may be provided.

10, 30 Engine 11 Cylinder block 11A Bore wall 12 Cylinder head 13 Cylinder bore 14 Piston 15 Combustion chamber 16 Intake port 17 Exhaust port 18 Intake valve 19 Exhaust valve 20 Spark plug 21, 31 Compressed air injector 23 Injection 24 Air compressor 25 Piston 33 1 nozzle 34 2nd nozzle 35 3rd nozzle L1, L2 Virtual line P Center of cylinder bore S Swirl flow T Tumble flow TDC Top dead center BDC Bottom dead center

Claims (3)

A cylinder bore that houses a reciprocating piston and
A combustion chamber formed in the cylinder bore by the piston and
A single intake port and a single exhaust port arranged with respect to the combustion chamber,
An intake valve that opens and closes the intake port and an exhaust valve that opens and closes the exhaust port are provided.
In an internal combustion engine in which a swirl flow is formed in the combustion chamber by intake air from the intake port in the intake stroke.
A compressed air injector is provided between the intake port and the exhaust port to form a tumble flow in the combustion chamber by injecting compressed air toward the bore wall in the combustion chamber in the intake stroke. ,
The injection direction of the compressed air injected from the compressed air injector toward the bore wall in a plan view of the combustion chamber passes through the injection port of the compressed air injector and in the intake passage connected to the intake port. It is included in the plane view fan-shaped range between the virtual line along the flow of the flowing intake air and the virtual line passing through the injection port of the compressed air injector and passing through the center of the intake port.
An internal combustion engine characterized in that the compressed air injected by the compressed air injector interferes with the swirl flow and the swirl flow is drawn into the tumble flow. The internal combustion engine according to claim 1 , wherein the compressed air injector injects compressed air when the piston descends to an intermediate point between top dead center and bottom dead center in an intake stroke . The internal combustion engine according to claim 1 or 2 , wherein the compressed air injector includes a plurality of nozzles that inject compressed air in a plurality of directions in the circumferential direction of the combustion chamber .

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