internal combustion engine

Abstract

To provide an internal combustion engine in which fuel spray is easily diffused uniformly.SOLUTION: An internal combustion engine includes a cylinder head, and a cavity formed on a top surface of a piston and forming a combustion chamber between the cylinder head and it. The cavity includes a first surface arranged in a center of the piston, a second surface arranged around the first surface and located closer to the cylinder head than the first surface, and a groove provided on the second surface and recessed to the first surface side.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to internal combustion engines. [Background technology]

[0002] Conventionally, an internal combustion engine having a cavity on the top surface of a piston is known (see, for example, Patent Document 1). The internal combustion engine of Patent Document 1 discloses a cavity with a two-stage structure. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2020-2866 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 discloses a cavity in which the spray hits the wall between the upper and lower stages and is diffused to the central and outer periphery of the piston top surface. In such a cavity, there may be too much spray in the central part of the top surface.

[0005] An object of the present disclosure is to provide an internal combustion engine in which spray is likely to diffuse uniformly. [Means for solving the problem]

[0006] The internal combustion engine according to the present disclosure includes a cylinder head, a cavity formed on a top surface of a piston and forming a combustion chamber between the cylinder head and the cavity, Center of the cylinder Established in At multiple locations inside the cavity a fuel injection valve that injects fuel, and the cavity has a first surface that is disposed at the center of the top surface of the piston, a second surface that is disposed around the first surface and is disposed closer to the cylinder head than the first surface, and a cavity that is disposed at the second surface multiple a groove portion recessed toward the first surface side, the fuel injection valve injects fuel toward the plurality of groove portions,The depth of the groove is shallower than the height from the first surface to the second surface.

[0007] According to this internal combustion engine, the spray spreads around the top surface of the piston through the grooves arranged in the second surface, which causes the spray to spread over both the first surface and the second surface, resulting in a uniform dispersion of the spray. [Effects of the Invention]

[0008] According to the present disclosure, an internal combustion engine can be provided in which spray is likely to diffuse uniformly. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view of an internal combustion engine according to an embodiment of the present disclosure; [Figure 2] FIG. 2 is a perspective view of a piston according to an embodiment of the present disclosure. [Figure 3] FIG. 2 is a top view of a piston according to an embodiment of the present disclosure. [Figure 4] Cross section AA of Figure 3. [Figure 5] FIG. 10 is a top view of a piston according to a second embodiment of the present disclosure. [Figure 6] FIG. 10 is a top view of a piston according to a third embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] First Embodiment Hereinafter, a first embodiment of the present disclosure will be described with reference to the drawings.

[0011] As shown in Fig. 1, the internal combustion engine 1 includes a cylinder block 2, a cylinder head 4, a piston 6, a plurality of intake valves 8, a plurality of exhaust valves 10, and a fuel injection valve 12. The internal combustion engine 1 of this embodiment is a direct injection diesel engine in which the fuel injection valve 12 directly injects fuel into a cylinder 21 of the cylinder block 2. In this embodiment, two intake valves 8 and two exhaust valves 10 are arranged in one cylinder 21. The internal combustion engine 1 of this embodiment will be described using an example in which the cylinders 21 are arranged in a vertical direction.

[0012] The internal combustion engine 1 also includes a swirl flow generating means. In this embodiment, the swirl flow generating means is two intake valves 8. In this embodiment, the lift heights of the two intake valves 8 are different, thereby generating a swirl flow in which the intake air swirls along a plane perpendicular to the sliding direction of the piston 6 (in this embodiment, the up-and-down direction). The internal combustion engine 1 of this embodiment will be described using an example in which the swirl flow swirls counterclockwise (see S in FIG. 3). Note that the swirl flow generating means may also be one in which the shape of the intake port of the cylinder head 4 or the like is formed so as to generate a swirl flow. Alternatively, a valve that generates a swirl flow may be provided.

[0013] The piston 6 has a cavity 61 on its top surface. When the piston 6 is at top dead center, the cavity 61 forms a combustion chamber between the piston 6 and the cylinder head 4. Therefore, it is preferable that the air-fuel mixture supplied to the cavity 61 is as homogeneous as possible. In the case of the direct injection diesel engine of this embodiment, it is preferable that the spray of fuel injected into the cavity 61 is diffused to form a homogeneous air-fuel mixture.

[0014] As shown in FIG. 2 , the cavity 61 has a first surface 62, a second surface 63, a groove 64, a vertical surface 65, and an outer peripheral wall 66. The first surface 62 is located in the center of the top surface of the piston 6. The second surface 63 is located around the first surface 62. The second surface 63 is located closer to the cylinder head 4 than the first surface 62. In this embodiment, the second surface 63 is located higher than the first surface 62. An outer peripheral wall 66 extending toward the cylinder head 4 is located around the second surface 63. A plurality of valve recesses 66a recessed toward the second surface are arranged at intervals in the circumferential direction on the outer peripheral wall 66 to avoid interference with the intake valve 8 and the exhaust valve 10.

[0015] A plurality of grooves 64 are provided on the second surface 63. The plurality of grooves 64 are recessed from the second surface 63 toward the first surface 62. The depth of the plurality of grooves 64 is shallower than the height between the first surface 62 and the second surface 63, and a vertical surface 65 extends between a bottom surface 64a of the groove 64 and the first surface 62.

[0016] The plurality of grooves 64 are formed radially on the second surface 63. As shown in FIG. 3, in this embodiment, four of the plurality of grooves 64 are formed radially. Therefore, the four grooves 64 are arranged every 90 degrees. In this embodiment, the width of the grooves 64 increases toward the periphery of the top surface of the piston 6. In other words, the grooves 64 are narrow at the inlet on the first surface 62 side and widen toward the periphery of the top surface. This makes it easy to adjust the amount of spray remaining on the first surface 62 and the amount of spray that reaches the periphery of the top surface.

[0017] As shown in FIG. 4, the second surface 63 is formed so that the upstream side in the swirling direction of the swirl flow is higher toward the cylinder head 4 than the downstream side in the swirling direction of the swirl flow. This causes the swirl flow to be pushed against the side wall 64b of the groove 64 and become turbulent. As a result, the spray supplied to the groove 64 is more likely to be diffused by the swirl flow, promoting mixing with the intake air and improving combustion. Furthermore, the turbulence of the swirl flow reduces the flow velocity of the mixture containing the spray supplied to the groove 64 and the heat transfer coefficient. This reduces cooling loss. Furthermore, the spray supplied to the groove 64 is more likely to be diffused by the swirl flow, promoting mixing with the intake air. This allows the internal combustion engine 1 to reduce the amount of fuel that adheres to the top surface of the piston 6.

[0018] Furthermore, the depth of the grooves 64 in this embodiment is shallower on the outer periphery side of the piston 6 than on the first surface 62 side. This makes it easier for the spray that passes through the grooves 64 to be diffused by a swirl flow formed between the outer periphery side of the grooves 64 and the outer periphery wall 66.

[0019] The vertical surface 65 extends from the first surface 62 toward the cylinder head 4 and is connected to the bottom surface 64 a of the groove portion 64 or the second surface 63 .

[0020] 1, the fuel injection valve 12 injects fuel toward a combustion chamber. In this embodiment, the fuel injection valve 12 injects fuel into a cavity 61. The fuel injection valve 12 of this embodiment is connected to a fuel injection device such as a high-pressure pump or a common rail, and injects high-pressure fuel to form a spray in the cavity 61.

[0021] The fuel injection valve 12 injects fuel toward the vertical surface 65. As shown in FIG. 3 , in this embodiment, the fuel injection valve 12 injects fuel in eight directions. Four of the eight fuel injection valves 12 inject fuel toward the direction in which the grooves 64 are located (an example of a first direction). Four of the eight fuel injection valves 12 inject fuel toward the direction in which the second surface 63 is located (an example of a second direction). In other words, the fuel injection valve 12 forms sprays (see F in FIG. 3 ) in the direction in which the grooves 64 are located and in the direction in which the second surface 63 is located, which is different from the direction in which the grooves 64 are located. The sprays in the direction in which the grooves 64 are located and the sprays in the direction in which the second surface 63 is located are adjacent to each other. That is, the fuel injection valve 12 in this embodiment has eight injection ports, and the eight injection ports are arranged so that the injection ports aimed at the grooves 64 and the injection ports aimed at the second surface 63 are alternately arranged. The second surface 63 and the groove 64 may be formed to match the injection port of the fuel injection valve 12.

[0022] In the internal combustion engine 1 configured as described above, when fuel is injected from the fuel injector 12, four of the eight sprays enter the grooves 64 and are supplied to the outer peripheral wall 66. The spray that has reached the outer peripheral wall 66 is diffused by a swirl flow. Meanwhile, four of the eight sprays hit the vertical surface 65 connecting the second surface 63 and the first surface 62, where they are split by the vertical surface 65. One of the sprays is pushed back toward the first surface 62, while the other is supplied along the second surface 63 to the outer peripheral wall 66. This causes the spray to be diffused to the center of the top surface of the piston 6. In this way, the shape of the cavity 61 of the internal combustion engine 1 allows the fuel to be uniformly diffused both to the center of the top surface and around the top surface. As a result, the air-fuel mixture becomes homogeneous, improving combustion.

[0023] Second Embodiment Next, a second embodiment of the present disclosure will be described with reference to Fig. 5. In the second embodiment, only the differences from the first embodiment will be described.

[0024] 5, a cavity 261 in the second embodiment has a first surface 262, a second surface 263, grooves 264, a vertical surface 265, and an outer peripheral wall 266. The second embodiment differs from the first embodiment in the number of grooves 264 in the cavity 261. The other configurations are the same as those in the first embodiment, and therefore will not be described.

[0025] In the second embodiment, eight grooves 264 are formed. The eight sprays are supplied to all eight grooves 264. As a result, the flow of the spray injected from the fuel injector 12 remains near the center of the top surface where the first surface 262 is located. On the other hand, as the number of grooves 264 increases, the unevenness on the outer periphery of the top surface increases, disrupting the flow of the mixture on the outer periphery of the top surface. When the flow of the spray mixture is disrupted, the flow velocity of the mixture decreases, and the heat transfer coefficient decreases. As a result, cooling loss can be reduced in this internal combustion engine 1.

[0026] <Third embodiment> Next, a third embodiment of the present disclosure will be described with reference to Fig. 6. In the third embodiment, only the differences from the first embodiment will be described.

[0027] 6, a cavity 361 in the third embodiment has a first surface 362, a second surface 363, a groove portion 364, a vertical surface 365, and an outer peripheral wall 366. The third embodiment differs from the first embodiment in that the width of the groove portion 364 of the cavity 361 narrows toward the periphery of the top surface of the piston 6. The other configurations are the same as those in the first embodiment, and therefore will not be described.

[0028] In this way, because the width of the groove 364 narrows toward the periphery of the top surface of the piston 6, the flow velocity of the spray increases toward the outer circumferential wall 366. The spray with increased flow velocity forms a strong upward flow along the outer circumferential wall 366 and swirls in the vertical direction. This promotes mixing of the spray with the intake air. Furthermore, because the spray forms a strong upward flow, flames heading toward the cylinder 21, which has a low wall temperature, can be suppressed. This reduces cooling loss in the internal combustion engine 1. Furthermore, as the spray approaches the outer periphery of the top surface, it hits the side wall 364b of the groove 364 and is divided into upper and lower parts, promoting diffusion of the spray toward the second surface 363. This makes it possible to utilize the wide space around the groove 364 to promote mixing of the spray and the intake air.

[0029] As described above, according to the present disclosure, it is possible to provide an internal combustion engine 1 in which the spray is likely to diffuse uniformly.

[0030] <Other embodiments> Although the present embodiment has been described above, the present disclosure is not limited to the above embodiment, and various modifications are possible within the scope of the gist of the invention. In particular, the multiple modifications described in this specification can be arbitrarily combined as necessary.

[0031] (a) For example, in the first embodiment described above, an example of the cavity 61 was described in which the depth of the groove portion 64 was shallower on the outer periphery of the piston 6 than on the first surface 62 side. However, the present disclosure is not limited to this. The depth of the groove portion 64 may be uniform from the outer periphery of the piston 6 to the spray inlet on the first surface 62 side. The combustion chamber space between the second surface 63 and the cylinder head 4 becomes wider toward the outer periphery of the top surface of the piston 6. Therefore, by making the depth of the groove portion 64 uniform from the outer periphery of the piston 6 to the spray inlet on the first surface 62 side, the swirl flow is more likely to hit the side wall 64b and become turbulent as the space widens toward the outer periphery. Therefore, the turbulence caused by the swirl flow can be more strongly formed toward the periphery of the top surface. As a result, the spray can be more diffused toward the periphery of the top surface. In this case, a groove narrower than the groove portion 64 of the first embodiment may be used. In this way, the influence of turbulence caused by the swirl flow can be adjusted by adjusting the width of the groove portion 64. The depth of the groove 64 may be deeper on the outer periphery side of the piston 6 than on the first surface 62 side. In this way, by making the depth of the groove 64 deeper on the outer periphery side of the piston 6 than on the first surface 62 side, the influence of turbulence due to the swirl flow may be adjusted.

[0032] (b) In the first embodiment described above, an example has been described in which the second surface 63 is formed higher on the upstream side in the swirling direction of the swirl flow toward the cylinder head 4 than on the downstream side in the swirling direction of the swirl flow, but the present disclosure is not limited to this. The height of the second surface 63 may be the same on the downstream side in the swirling direction of the swirl flow and on the upstream side in the swirling direction of the swirl flow. [Explanation of symbols]

[0033] 1: Internal combustion engine 2: Cylinder block 4: Cylinder head 6: Piston 8: Intake valve 10: Exhaust valve 12: Fuel injection valve 21: Cylinder 61,261,361:Cavity 62,262,362: 1st page 63,263,363:Second side 64,264,364: Groove 65,265,365:Vertical surface

Claims

1. A cylinder head, a cavity formed in a top surface of the piston, forming a combustion chamber between the piston and the cylinder head; a fuel injection valve provided in a central portion of the cylinder and configured to inject fuel into a plurality of locations within the cavity; Equipped with The cavity has a first surface disposed at a center portion of a top surface of the piston, a second surface disposed around the first surface and disposed closer to the cylinder head than the first surface, and a plurality of grooves provided in the second surface and recessed toward the first surface, the fuel injection valve injects fuel toward the plurality of groove portions, The depth of the groove is shallower than the height from the first surface to the second surface. Internal combustion engine.

2. the cavity has a vertical surface that extends from the first surface toward the cylinder head and is connected to the groove portion or the second surface, The fuel injection valve injects fuel toward the vertical surface.

2. The internal combustion engine according to claim 1.

3. the fuel injection valve injects the fuel to form a spray in a first direction and a second direction different from the first direction, The spray in the first direction is formed toward the groove portion, The spray in the second direction is formed toward the second surface, The spray in the first direction and the spray in the second direction are formed adjacent to each other.

3. An internal combustion engine according to claim 1 or 2.

4. a swirl flow generating means for generating, in the combustion chamber, a swirl flow that swirls along a plane perpendicular to the sliding direction of the piston, the second surface is formed so that an upstream side in the swirling direction of the swirl flow is higher toward the cylinder head than a downstream side in the swirling direction of the swirl flow. An internal combustion engine according to any one of claims 1 to 3.

5. The width of the groove increases toward the outer periphery of the top surface.

5. An internal combustion engine according to any one of claims 1 to 4.

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