Internal combustion engine

Abstract

To provide an internal combustion engine capable of optimizing combustion.SOLUTION: An internal combustion engine has a spark plug provided in a central portion of a ceiling of a combustion chamber of the internal combustion engine, an injector provided in the central portion of the ceiling for injecting fuel into the combustion chamber, an intake valve provided in the internal combustion engine, and an exhaust valve provided in the internal combustion engine. From one side of the internal combustion engine to an opposite side, the exhaust valve, the spark plug, the injector and the intake valve are arranged in this order. The injector sprays the fuel in a plurality of directions, and an angle between the spray closest to the exhaust valve among the plurality of sprays and the exhaust valve is 21° to 34°.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an internal combustion engine.

Background Art

[0002] An in-cylinder direct injection type internal combustion engine that injects fuel into the combustion chamber of an internal combustion engine is used. There is a technique for controlling the direction of fuel spray and spraying the fuel toward the vicinity of the spark plug (Patent Document 1). It is possible to raise the temperature of the exhaust gas during cold start.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] An injector may be provided at the center of the ceiling of the combustion chamber. By spraying in the vicinity of the spark plug and directing the flame in the direction of the spray, stable combustion is achieved. It is possible to reduce emissions, etc. On the other hand, as the combustion speed increases, the vibration force increases, and there is a risk of generating noise. Therefore, an object of the present invention is to provide an internal combustion engine capable of optimizing combustion.

Means for Solving the Problems

[0005] The above object is achieved by providing an internal combustion engine with A combustion chamber is formed in the cylinder, and the a spark plug provided at the center of the ceiling of the combustion chamber, an injector provided at the center of the ceiling for injecting fuel into the combustion chamber, an intake valve provided in the internal combustion engine, and an exhaust valve provided in the internal combustion engine, wherein, from one side of the internal combustion engine toward the opposite side, the exhaust valve, the spark plug, the injector, and the intake valve are arranged in this order, With respect to the extending direction of the cylinder, the ignition plug is inclined toward the exhaust valve side, and the injector is inclined toward the intake valve side. the injector sprays the fuel in a plurality of directions, and the plurality of sprays includes a first spray that is the spray closest to the exhaust valve, a second spray that is the spray closest to the intake valve, and a third spray that faces between the first spray and the second spray. Among the plurality of sprays, the center of the first spray and the bottom surface of the closed valve the exhaust valve of can be achieved by an internal combustion engine in which the angle between the exhaust valve and the intake valve is 21° or more and 34° or less.

Advantages of the Invention

[0006] An internal combustion engine capable of optimizing combustion can be provided.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0008] Hereinafter, the internal combustion engine of the present embodiment will be described with reference to the drawings. FIG. 1(a) is a schematic diagram illustrating an internal combustion engine 10 according to the embodiment. The internal combustion engine 10 is, for example, a gasoline engine and has a cylinder block 20 and a cylinder head 21.

[0009] As shown in FIG. 1(a), a cylinder head 21 is attached on the cylinder block 20, and a crankcase (not shown) is attached under the cylinder block 20. A piston 22 is housed inside the cylinder block 20. The piston 22 is connected to a crankshaft through a connecting rod. The piston 22 is slidable in the vertical direction of FIG. 1(a). The combustion chamber 24 is defined by the cylinder block 20, the cylinder head 21, and the piston 22. The inner wall of the cylinder head 21 serves as the ceiling of the combustion chamber 24.

[0010] An intake port 26 and an exhaust port 28 are connected to the cylinder head 21. An intake passage 12 is connected to the upstream side of the intake port 26. An exhaust passage 14 is connected to the downstream side of the exhaust port 28.

[0011] An air cleaner 15, an air flow meter 16, and a throttle valve 18 are provided in the intake passage 12 in order from the upstream side. The air cleaner 15 removes dust and the like from the air in the intake passage 12 and purifies the air. The air flow meter 16 detects the flow rate of the air in the intake passage 12. The throttle valve 18 adjusts the flow rate of the air. The greater the opening degree of the throttle valve 18, the greater the air flow rate. The smaller the opening degree of the throttle valve 18, the smaller the air flow rate. A catalyst 29 is provided in the exhaust passage 14.

[0012] An intake valve 17, an exhaust valve 19, a spark plug 30, and an injector 32 are provided in the cylinder head 21. The intake valve 17 and the exhaust valve 19 are opened and closed by a valve operating mechanism (not shown). When the intake valve 17 opens, the intake port 26 and the combustion chamber 24 communicate with each other. When the exhaust valve 19 opens, the exhaust port 28 and the combustion chamber 24 communicate with each other.

[0013] The spark plug 30 and the injector 32 are provided at the center of the ceiling of the combustion chamber 24. The center portion is a position sandwiched between the intake port 26 and the exhaust port 28. The spark plug 30 and the injector 32 are inclined with respect to the extending direction of the cylinder of the internal combustion engine 10 (the vertical direction in Fig. 1(a)). The spark plug 30 is inclined toward the exhaust valve 19 side. The injector 32 is inclined toward the intake valve 17 side. The tip of the spark plug 30 and the tip of the injector 32 are exposed inside the combustion chamber 24. A plurality of injection ports are provided at the tip of the injector 32. The injector 32 injects fuel in a plurality of directions.

[0014] The spark plug 30 is positioned between the exhaust valve 19 and the injector 32. The injector 32 is positioned between the spark plug 30 and the intake valve 17. That is, as shown in Fig. 1(a), looking from one inner wall of the internal combustion engine 10 toward the opposite inner wall, the exhaust valve 19, the spark plug 30, the injector 32, and the intake valve 17 are arranged in this order.

[0015] Fig. 1(b) is a schematic diagram illustrating the internal combustion engine 10, showing the state where the intake valve 17 is open. When the intake valve 17 opens, air flows into the combustion chamber 24 from the intake port 26. As indicated by the arrow in Fig. 1(b), the air forms a longitudinal vortex, i.e., a tumble flow, inside the combustion chamber 24. The tumble flow flows along the ceiling of the combustion chamber 24 from the intake port 26 toward the intake valve 17, and flows along the side wall of the combustion chamber 24 and the upper surface of the piston 22.

[0016] The ECU (Electronic Control Unit) 11 is a control device equipped with computing devices such as a CPU (Central Processing Unit), and storage devices such as a flash memory, a ROM (Read Only Memory), and a RAM (Random Access Memory). The ECU 11 acquires the air flow rate detected by the air flow meter 16. The ECU 11 controls the fuel injection amount and injection timing from the injector 32. The ECU 11 controls the opening degree of the throttle valve 18.

[0017] The injector 32 injects fuel into the combustion chamber 24 (in-cylinder injection). More specifically, as will be described later, the injector 32 sprays fuel in a plurality of directions. When the intake valve 17 opens, air is introduced into the combustion chamber 24 from the intake port 26 as shown in Fig. 1(b). Inside the combustion chamber 24, an air-fuel mixture is generated. When the spark plug 30 ignites the air-fuel mixture, the air-fuel mixture burns. Due to the combustion of the air-fuel mixture, the piston 22 reciprocates up and down. Power is transmitted from the piston 22 to the crankshaft, and the crankshaft rotates. When the exhaust valve 19 opens, the exhaust after combustion is discharged to the exhaust port 28. The catalyst 29 purifies the exhaust.

[0018] Figures 2(a) and 2(b) are schematic diagrams illustrating the internal combustion engine 10, showing the state in which the injector 32 injects fuel. Let the example of Fig. 2(a) be the internal combustion engine 10A. Let the example of Fig. 2(b) be the internal combustion engine 10B. The internal combustion engines 10A and 10B are examples of the internal combustion engine of the present embodiment. As shown in Figs. 2(a) and 2(b), spraying is performed in a plurality of directions from the injector 32. Among the sprays injected from the injector 32, the one closest to the exhaust port 28 is defined as spray A, the central one is defined as spray B, and the one closest to the intake port 26 is defined as spray C. The dotted lines in the figure are virtual lines passing through the centers of the respective sprays.

[0019] The direction of spray A is different between the example of Fig. 2(a) and the example of Fig. 2(b). Let the angle between the bottom surface of the exhaust valve 19 in Fig. 2(a) and the center of spray A be θ1. Let the angle between the bottom surface of the exhaust valve 19 in Fig. 2(b) and the center of spray A be θ2. θ1 and θ2 are in the range of 21° or more and 34° or less. θ1 is larger than θ2. In the internal combustion engines 10A and 10B, the directions of spray B are the same as each other, and the directions of spray C are the same as each other. Depending on the direction of the spray, a difference occurs in the flame propagation direction in the combustion chamber 24. The combustion speed is determined by the flame propagation direction.

[0020] Fig. 3(a) is a schematic diagram showing a flame. The broken line in the figure indicates the flame generated in the combustion chamber 24 by the ignition of the spark plug 30. The flame F1 spreads toward the intake valve 17 side. The flame F2 spreads toward the intake valve 17 side, but is generated closer to the center of the combustion chamber 24 than the flame F1. The flame F3 is generated near the center of the combustion chamber 24. The flame F4 spreads toward the exhaust valve 19 side, but is generated closer to the center side than the flame F5. The flame F5 spreads toward the exhaust valve 19 side.

[0021] Fig. 3(b) is a schematic diagram illustrating the timing of heat generation. The horizontal axis indicates flames F1 to F5. The vertical axis indicates the timing (phase of ATDC (After Top Dead Center)) when a predetermined amount of heat is generated. The lower side of the vertical axis is the advanced angle side, and the upper side is the retarded angle side. On the lower side (advanced angle side) of the vertical axis, combustion is faster and heat is generated earlier than on the upper side (retarded angle side).

[0022] Towards flames F1 to F5, the heat generation timing is on the advanced angle side. That is, towards flames F1 to F5, the combustion speed increases. The heat generation timing of flame F1 is on the most retarded angle side. This is because combustion is slow and the combustion speed is low in flame F1. The heat generation timing of flame F5 is on the most advanced angle side. This is because the combustion speed is high in flame F5.

[0023] A high combustion speed enables efficient combustion, which can improve fuel efficiency and reduce exhaust emissions. However, the greater the combustion speed, the greater the vibration force and the greater the risk of noise generation. When the combustion speed decreases, the vibration force decreases and noise can be suppressed. To improve fuel efficiency, etc., it is preferable to generate flames F4 and F5 to increase the combustion speed. To suppress noise, etc., it is preferable to generate flames F1 and F2 to decrease the combustion speed.

[0024] Figs. 4(a) and 4(b) are diagrams illustrating the frequency and ratio of flame generation. The bar graph represents the frequency of the flame. The line graph is the ratio obtained by accumulating the frequencies. The left vertical axis indicates the frequency of the flame. The right vertical axis indicates the ratio of the frequency. Fig. 4(a) shows the frequency and ratio in the example of Fig. 2(a) (internal combustion engine 10A). Fig. 4(b) shows the frequency and ratio in the example of Fig. 2(b) (internal combustion engine 10B).

[0025] As shown in Fig. 4(a), in internal combustion engine 10A, the frequency of flame F4 is the highest. The frequency of flame F3 is the second highest, and the frequency of flame F5 is the third highest. As shown in Fig. 4(b), in internal combustion engine 10B, the frequency of flame F4 is the highest. The frequency of flame F5 is the second highest.

[0026] The frequencies of flames F4 and F5 in the internal combustion engine 10B are higher than those in the internal combustion engine 10A. The frequencies of flames F1 to F3 in the internal combustion engine 10A are higher than those in the internal combustion engine 10B. The difference in the frequencies of the flames is due to the direction of the spray A.

[0027] As shown in FIG. 1(b), the air flowing in from the intake port 26 forms a tumble flow. The tumble flow flows along the ceiling of the combustion chamber 24, the bottom surface of the exhaust valve 19, and the side surface of the combustion chamber 24.

[0028] In the internal combustion engine 10B shown in FIG. 2(b), the angle θ2 between the center of the spray A and the bottom surface of the exhaust valve 19 is smaller than the angle θ1 in the internal combustion engine 10A shown in FIG. 2(a). The spray A in FIG. 2(b) faces a direction close to the tumble flow of the air. For this reason, the tumble flow merges with the spray A in a strong state. The momentum of the spray A and the momentum of the tumble flow are combined, and the fuel easily flows with the tumble flow. In other words, a strong tumble flow containing fuel is formed. The flame easily flows in the direction of the exhaust valve 19 together with the tumble flow. That is, the flames F4 and F5 shown in FIG. 3(a) are likely to occur. For this reason, in FIG. 4(b), the ratios of the flames F4 and F5 are larger than those in FIG. 4(a).

[0029] On the other hand, the angle θ1 between the center of the spray A and the bottom surface of the exhaust valve 19 in the example shown in FIG. 2(a) is larger than the angle θ2 in the example shown in FIG. 2(b). The spray A in FIG. 2(a) faces a direction different from the tumble flow of the air. Since the tumble flow flows in a direction different from the spray A, it becomes difficult for the spray A to be carried by the tumble flow. The flame becomes difficult to flow in the direction of the exhaust valve 19. The flames F4 and F5 are less likely to occur. For this reason, in the example of FIG. 4(a), the ratios of the flames F4 and F5 are smaller than those in the example of FIG. 4(b), and the ratios of the flames F1 to F3 are larger.

[0030] FIG. 4(c) is a diagram illustrating the heat generation rate. The horizontal axis represents the crank angle. The vertical axis represents the heat generation rate. The solid line is an example of the internal combustion engine 10A. The dashed line is an example of the internal combustion engine 10B.

[0031] As shown in FIG. 4(c), the heat generation rate shows a peak. The peak of the internal combustion engine 10A is wider and lower than the peak of the internal combustion engine 10B. The peak of the internal combustion engine 10B is narrower and higher than the peak of the internal combustion engine 10A. The peak of the internal combustion engine 10B is located on the advanced angle side compared to the peak of the internal combustion engine 10A.

[0032] In the internal combustion engine 10A of FIG. 4(a), the ratio of flames F1 to F3 is larger than that of the internal combustion engine 10B in FIG. 4(b), so the combustion speed becomes smaller. The combustion becomes slow, and the generation of heat also becomes slow as shown by the solid line in FIG. 4(c). For this reason, the excitation force decreases, and noise can be suppressed. In the internal combustion engine 10B of FIG. 4(b), the ratio of flames F4 and F5 is larger than that of the internal combustion engine 10A in FIG. 4(a), so the combustion speed becomes larger. Since the combustion is fast, heat is generated rapidly as shown by the broken line in FIG. 4(c). For this reason, improvement of fuel consumption, reduction of exhaust emissions, etc. are possible.

[0033] According to the present embodiment, as shown in FIG. 1(a), the ignition plug 30 and the injector 32 are located at the center of the ceiling of the combustion chamber 24. The exhaust valve 19, the ignition plug 30, the injector 32, and the intake valve 17 are arranged in this order. The injector 32 injects fuel in a plurality of directions. The angle between the spray A closest to the exhaust valve 19 among the plurality of sprays and the bottom surface of the exhaust valve 19 is set to be 21° or more and 34° or less. By adjusting the angle to an appropriate size, the combustion speed is controlled and the combustion is optimized.

[0034] In the internal combustion engine 10A shown in Fig. 2(a), the angle between the center of the spray A and the bottom surface of the valve is denoted as θ1. In the internal combustion engine 10B shown in Fig. 2(b), the angle between the center of the spray A and the bottom surface of the valve is set to θ2, which is smaller than θ1. In the internal combustion engine 10A, since the angle θ1 is larger than θ2, the spray A is directed in a direction different from the tumble flow. As a result, it becomes difficult for the fuel to flow with the tumble flow, and the combustion becomes slow. The slow combustion reduces the excitation force and can suppress the noise. In the internal combustion engine 10B, since the angle θ2 is smaller than θ1, the spray A is directed in a direction closer to the tumble flow. The fuel merges into the strong tumble flow, and the combustion becomes faster. The faster combustion enables improvements in fuel efficiency, reduction of exhaust emissions, etc.

[0035] The angle between the spray and the bottom surface of the exhaust valve 19 may be adjusted according to the purpose. Laser processing or the like is performed at the tip of the injector 32 to form the injection port. By changing the position, orientation, size, etc. of the injection port, the direction of the spray can be adjusted.

[0036] The ranges of the angles θ1 and θ2 are 21° or more and 34° or less. If the angle is less than 21°, for example, the spray A may get closer to the spark plug 30, and there is a risk that the ignition by the spark plug 30 may be inhibited. If the angle is 34° or more, the distance between the spark plug 30 and the spray A increases, and there is a risk that the combustion may become unstable. By setting the angle to be 21° or more and 34° or less, the distance between the spray A and the spark plug 30 is appropriately maintained, enabling stable combustion. The lower limit of the angle may be, for example, 22° or more, 23° or more, 24° or more, 25° or more, etc. The upper limit of the angle may be, for example, 33° or less, 32° or less, 31° or less, 30° or less, etc.

[0037] Figs. 2(a) and 2(b) show examples where the injector 32 sprays in multiple directions. The number of sprays can be changed. The angle between the spray A closest to the exhaust valve 19 among the sprays and the bottom surface of the exhaust valve 19 is adjusted within the range of 21° to 34°. Depending on the angle, the strength of the tumble flow flowing into the spray A changes, and the combustion speed can be varied.

[0038] Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

Explanation of Reference Numerals

[0039] 10, 10A, 10B Internal combustion engine 11 ECU 12 Intake passage 14 Exhaust passage 15 Air cleaner 16 Airflow meter 17 Intake valve 18 Throttle valve 19 Exhaust valve 20 Cylinder block 21 Cylinder head 22 Piston 24 Combustion chamber 26 Intake port 28 Exhaust port 29 Catalyst 30 Spark plug 32 Injector

Claims

【Claim 1】 A combustion chamber is formed in a cylinder of an internal combustion engine, an ignition plug provided at the center of the ceiling of the combustion chamber, an injector provided at the center of the ceiling and injecting fuel into the combustion chamber, an intake valve provided in the internal combustion engine, an exhaust valve provided in the internal combustion engine, and comprising: From one side of the internal combustion engine toward the opposite side, the exhaust valve, the ignition plug, the injector, and the intake valve are arranged in this order, With respect to the extending direction of the cylinder, the ignition plug is inclined toward the exhaust valve side, and the injector is inclined toward the intake valve side, The injector sprays the fuel in a plurality of directions, The plurality of sprays include a first spray that is the spray closest to the exhaust valve, a second spray that is the spray closest to the intake valve, and a third spray that faces between the first spray and the second spray, An internal combustion engine in which an angle between the center of the first spray among the plurality of sprays and the bottom surface of the closed exhaust valve is 21° or more and 34° or less.

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