engine

Abstract

To provide a sub-chamber ignition plug that allows for sufficient scavenging of the sub-chamber. [Solution] In an engine equipped with a sub-chamber spark plug 20, a sub-chamber C2 is formed by a torch sleeve 30 mounted on the cylinder head and having nozzles 33, 33, ..., 34, and a spark plug 40. The tip portion 32 of the torch sleeve 30 that protrudes from the cylinder head has a tapered shape, more specifically a tapered shape, where the diameter decreases towards the piston, and nozzles 33, 33, ... are provided in this tapered portion.

Description

Technical Field

[0001] The present invention relates to an engine. In particular, the present invention relates to an improvement in an engine provided with a sub-chamber ignition plug.

Background Art

[0002] Conventionally, as disclosed in Patent Document 1 and Patent Document 2 for example, an engine that operates on gaseous fuels such as natural gas and hydrogen and includes a sub-chamber ignition plug is known. This type of engine compresses the fresh air (a mixture of air and gaseous fuel) supplied from the intake port to the main chamber (main combustion chamber) by the upward movement of the piston, allows the compressed fresh air to flow into the sub-chamber of the sub-chamber ignition plug, and generates a flame in the sub-chamber by igniting the sub-chamber ignition plug. Then, the flame generated in the sub-chamber is ejected as a torch flame from the nozzle of the sub-chamber ignition plug into the main chamber, thereby spreading the combustion of the fresh air in the main chamber.

[0003] Patent Document 1 discloses that the torch flame ejected due to the pressure difference with the main chamber communicated by the nozzle of the sub-chamber ignition plug enables rapid combustion of the air-fuel mixture in the main chamber.

[0004] Also, Patent Document 2 discloses that by generating a tumble flow in the sub-chamber and scavenging the residual gas in the sub-chamber, the combustion performance in the sub-chamber is improved.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] In engines equipped with a sub-chamber spark plug, it is required that the sub-chamber be sufficiently scavenged after the combustion stroke. However, in the case disclosed in Patent Document 1, the high-temperature residual combustion gas from the previous cycle in the area surrounded by the ground electrode and insulator is not scavenged and mixed with the fresh air flowing in from the main chamber in the current cycle, and the heat of the residual gas may cause pre-ignition.

[0007] Furthermore, in the invention disclosed in Patent Document 2, it was difficult to effectively scavenge the high-temperature residual combustion gas that had entered the gap between the central electrode insulator of the spark plug, located at the upper back of the sub-chamber, and the metal shell.

[0008] The present invention has been made in view of the above, and its object is to provide a sub-chamber ignition plug that can adequately scavenge the sub-chamber. [Means for solving the problem]

[0009] The present invention provides a solution for achieving the aforementioned objectives, based on an engine equipped with a pre-chamber spark plug. This engine forms a pre-chamber with a torch sleeve mounted on the cylinder head and having a nozzle, and a spark plug, wherein the tip of the torch sleeve protruding from the cylinder head has a tapered shape in which the diameter decreases toward the piston, and the nozzle is provided in the tapered portion.

[0010] This specific design allows for a shorter distance between the nozzle of the torch sleeve and the combustion gas residue area around the tip of the spark plug (e.g., the insulator pocket between the insulator of the spark plug's center electrode and the metal shell), enabling the fresh air flowing from the nozzle into the sub-chamber to reach the combustion gas residue area while maintaining a high flow velocity. Furthermore, the inner diameter of the sub-chamber can be reduced (making the flow of fresh air within the sub-chamber more compact), which allows the fresh air to reach the combustion gas residue area more easily. These effects enable effective scavenging of combustion gases remaining in the residue area, thereby suppressing pre-ignition.

[0011] More specifically, the tapered portion of the torch sleeve is tapered in shape.

[0012] According to this, the distance between the nozzle of the torch sleeve and the combustion gas residue area can be significantly shortened, and the tapered shape can be optimized to effectively scavenge the combustion gases remaining in the combustion gas residue area.

[0013] Furthermore, when viewed from a direction along the central axis of the tapered portion, the central axis of the nozzle is inclined within an angular range of 0° and an upper limit of 60° with respect to the tangential direction to the outer edge of the tapered portion, from the main chamber side to the sub-chamber side of the engine, and when viewed from a direction perpendicular to the central axis of the tapered portion, it is directed towards the vicinity of the spark plug electrode, from the main chamber side to the sub-chamber side.

[0014] According to this, when fresh air flows from the main chamber to the secondary chamber through the nozzle, a swirling flow of fresh air is generated in the secondary chamber, effectively scavenging the residual combustion gas area. Furthermore, if the electrodes of the spark plug and the opening position of the nozzle (the position of the opening facing the secondary chamber) are close together, and if multiple nozzles are provided in the circumferential direction of the secondary chamber, the positions of adjacent nozzles in that circumferential direction will also be close together, thus reducing the variation in the torch flame ejected from each nozzle into the main chamber. In addition, after ignition by the spark plug, the swirling flow generated in the secondary chamber accelerates combustion in that chamber, increasing the penetrating force of the torch flame ejected into the main chamber, which also reduces the variation in the torch flame ejected from each nozzle towards the main chamber. Due to these effects, combustion can be carried out uniformly throughout the main chamber, and engine knocking can be suppressed.

[0015] The direction of the torch flame ejected from the sub-chamber into the main chamber by the nozzle is opposite to the direction of the intake swirl formed in the main chamber by the intake port of the engine.

[0016] In engines that do not have a fuel supply system to the sub-chamber other than the aforementioned nozzles, there is a concern that the combustion speed in the main chamber will be low because the temperature of the torch flame ejected into the main chamber is relatively low, the amount of the torch flame is relatively small, and the penetrating force of the torch flame is relatively small. In this case, if the intake air (mixture) between adjacent torch flames ejected from each of the multiple nozzles can be burned early, the ratio of surface area to volume of the burned area can be reduced, and the temperature near the flame surface can be kept high, thereby maintaining a high combustion speed in the main chamber. In view of this, in this solution, by setting the direction of the torch flame ejected into the main chamber and the direction of the intake air swirl in opposite directions, the torch flame does not develop radially (towards the cylinder wall) but develops circumferentially, and the intake air between adjacent torch flames is burned early, making it possible to maintain a high combustion speed in the main chamber.

[0017] Furthermore, the direction of the torch flame ejected from the sub-chamber into the main chamber by the nozzle may be the same as the direction of the intake swirl formed in the main chamber by the intake port of the engine.

[0018] This solution is effective when the temperature of the torch flame ejected into the main chamber is relatively high, the amount of the torch flame is relatively large, and the penetrating power of the torch flame is relatively large. In other words, by making the direction of the torch flame ejected into the main chamber the same as the direction of the intake swirl, the torch flame can be rapidly diffused over a wide area by utilizing this swirl, thereby making it possible to obtain a high combustion rate in the main chamber.

[0019] Furthermore, the tapered portion of the torch sleeve is positioned to begin from the bottom surface of the cylinder head.

[0020] According to this, the area of ​​the portion of the torch sleeve facing the main chamber can be reduced while obtaining the aforementioned effects. In other words, the heat-receiving area of ​​the torch sleeve from the combustion gas in the main chamber can be reduced. As a result, the temperature rise of the torch sleeve can be suppressed, and the temperature rise of the fresh air in the secondary chamber can be suppressed. [Effects of the Invention]

[0021] In this invention, an engine equipped with a sub-chamber spark plug, in which a sub-chamber is formed by a torch sleeve and a spark plug, has a tapered tip and a nozzle provided at the tapered portion. This shortens the distance between the nozzle of the torch sleeve and the combustion gas residue area around the tip of the spark plug, allowing the fresh air flowing from the nozzle into the sub-chamber to reach the combustion gas residue area while maintaining a high flow velocity. As a result, it becomes possible to effectively scavenge the combustion gases remaining in the combustion gas residue area, thereby suppressing pre-ignition. [Brief explanation of the drawing]

[0022] [Figure 1] It is a schematic diagram near the combustion chamber in the engine according to the embodiment. [Figure 2] Fig. 2(a) is a bottom view of the sub-chamber ignition plug in the embodiment, Fig. 2(b) is a cross-sectional view taken along line B-B in Fig. 2(a), and Fig. 2(c) is a cross-sectional view taken along line C-C in Fig. 2(a). [Figure 3] It is a diagram showing the shape of the sub-chamber of the sub-chamber ignition plug according to the embodiment by a two-dot chain line. [Figure 4] It is a view of the main chamber as seen from the piston side in the embodiment. [Figure 5] Fig. 5(a) is a bottom view of the sub-chamber ignition plug in the modified example, Fig. 5(b) is a cross-sectional view taken along line B-B in Fig. 5(a), and Fig. 5(c) is a cross-sectional view taken along line C-C in Fig. 5(a). [Figure 6] It is a diagram showing the shape of the sub-chamber of the sub-chamber ignition plug according to the modified example by a two-dot chain line. [Figure 7] Fig. 7(a) is a bottom view of the sub-chamber ignition plug in the comparative example, Fig. 7(b) is a cross-sectional view taken along line B-B in Fig. 7(a), and Fig. 7(c) is a cross-sectional view taken along line C-C in Fig. 7(a). [Figure 8] It is a diagram showing the shape of the sub-chamber of the sub-chamber ignition plug according to the comparative example by a two-dot chain line. [Figure 9] It is a diagram showing an example of the shape of the torch flame when the main chamber is viewed from the piston side. Fig. 9(a) shows the case of the embodiment, Fig. 9(b) shows the case of the modified example, and Fig. 9(c) shows the case of the comparative example. [[ID=X]] [Figure 10] It is a diagram showing the result of simulation calculation of the amount of carbon dioxide in the sub-chamber during the period from the intake stroke to the compression stroke of the engine in each of the embodiment, the modified example, and the comparative example.

Mode for Carrying Out the Invention

[0023] Hereinafter, embodiments of the present invention will be described based on the drawings. This embodiment will describe the case where the present invention is applied to a hydrogen engine.

[0024] -Engine Overview- Figure 1 is a schematic diagram of the area near the combustion chamber in the engine 10 according to this embodiment. As shown in Figure 1, the engine 10 is equipped with a sub-chamber spark plug 20. The engine 10 includes a cylinder block 11 that constitutes the cylinder bore, and a cylinder head 15 attached to the upper part of the cylinder block 11. The sub-chamber spark plug 20 is attached to the lower part of the cylinder head 15 in the central part of the cylinder bore. A piston 12 is disposed inside the cylinder block 11 so as to be able to move back and forth, and the space enclosed by the cylinder block 11, piston 12 and cylinder head 15 is the main combustion chamber, or main chamber C1, and a sub-chamber C2 that communicates with the main chamber C1 is provided at the tip of the sub-chamber spark plug 20 (the lower end in Figure 1). The configuration for providing this sub-chamber C2 will be described later.

[0025] When the engine 10 is running, fresh air (intake), a mixture of air and fuel (hydrogen), is introduced into the main chamber C1 through an intake port 13 provided in the cylinder head 15. As the piston 12 rises, the compressed fresh air flows into the sub-chamber C2. In the sub-chamber C2, the sub-chamber spark plug 20 is ignited at a predetermined timing, and a flame is generated by the combustion of the fresh air. This flame is then ejected from the sub-chamber C2 into the main chamber C1 as a torch flame, thereby spreading the combustion of the fresh air in the main chamber C1. This combustion of fresh air in the main chamber C1 pushes down the piston 12, generating the driving force for the engine 10. The exhaust gas after combustion is discharged from the main chamber C1 through an exhaust port 14 provided in the cylinder head 15.

[0026] Immediately after ignition and combustion in the sub-chamber spark plug 20, high-temperature residual combustion gases remain in the sub-chamber C2. When fresh air flows in from the main chamber C1 in the current cycle while high-temperature residual combustion gases from the previous cycle remain in the sub-chamber C2, pre-ignition is more likely to occur if the scavenging of the high-temperature residual combustion gases and the mixing of the high-temperature residual combustion gases with the fresh air do not occur properly with the inflow of fresh air.

[0027] The sub-chamber spark plug 20 according to this embodiment is characterized by its ability to promote the scavenging and mixing of high-temperature residual combustion gases in the sub-chamber C2 when fresh air flows in from the main chamber C1, thereby suppressing pre-ignition. The configuration of the sub-chamber spark plug 20 will be described below.

[0028] -Configuration of the sub-chamber spark plug- Figure 2 shows the main parts of the sub-chamber spark plug 20 in this embodiment, where Figure 2(a) is a bottom view of the sub-chamber spark plug 20, Figure 2(b) is a cross-sectional view along line BB in Figure 2(a), and Figure 2(c) is a cross-sectional view along line CC in Figure 2(a). As shown in Figures 1 and 2, the sub-chamber spark plug 20 is composed of a torch sleeve 30 and a spark plug 40.

[0029] The torch sleeve 30 has a bottomed cylindrical shape and has a space inside for housing the spark plug 40. The spark plug 40 is housed inside the torch sleeve 30. As shown in Figure 1, for example, a female thread 31 is provided on the inner circumferential surface near the tip of the torch sleeve 30, and a male thread 41 is provided on the outer circumferential surface near the tip of the spark plug 40. The male thread 41 of the spark plug 40 is screwed into the female thread 31 of the torch sleeve 30, thereby mounting the spark plug 40 inside the torch sleeve 30. In this state, with the spark plug 40 mounted inside the torch sleeve 30, a space with a predetermined volume is formed between the tip of the torch sleeve 30 and the tip of the spark plug 40, and this space functions as a sub-chamber C2.

[0030] As shown in Figure 1, the spark plug 40 has a configuration in which an insulator 42 is supported by a plug body 43. The plug body 43 is made of a heat-resistant material (for example, a metal such as nickel). As shown in Figures 2(b) and 2(c), a central electrode 44, which is the negative electrode, and a ground electrode 45, which is the positive electrode, are arranged at a predetermined distance apart at the tip of the plug body 43, facing the sub-chamber C2. The central electrode 44 penetrates the insulator 42 and reaches the external terminal 46 (see Figure 1). When a voltage is applied between the central electrode 44 and the ground electrode 45, ignition occurs between these electrodes 44 and 45, and combustion (flame generation) takes place in the sub-chamber C2. The other components of the spark plug 40 are well known, so their explanation is omitted here.

[0031] As shown in Figures 1, 2(b), and 2(c), the tip portion 32 of the torch sleeve 30 has a tapered shape where the diameter gradually decreases towards the piston 12, with the portion protruding from the cylinder head 15 (facing the main chamber C1) being tapered. Multiple nozzles 33, 33, ..., 34 are provided on this tapered portion (tip portion 32). Specifically, the tip portion 32 of the torch sleeve 30 has a tapered shape. In this invention, the tapered shape is not limited to a tapered shape (conical shape), but also includes shapes with curved cross-sections such as spheres and egg shapes.

[0032] More specifically, the tip portion 32 of the torch sleeve 30 has a tapered portion 35 that slopes toward the central axis of the torch sleeve 30 as it approaches the piston 12 (with its inner surface shaped like a mortar), and a bottom plate portion 36 that is continuous with the lower end of the tapered portion 35 and extends in a direction perpendicular to the central axis of the torch sleeve 30. The angle of inclination of the tapered portion 35 is not particularly limited, but in this embodiment, for example, it has an angle of inclination of about 60° with respect to the horizontal. This value is not limited to this and can be set as appropriate.

[0033] The tip 32 of the torch sleeve 30 is provided with nozzles 33, 33, ..., 34. These nozzles 33, 33, ..., 34 are composed of through holes provided in the tapered portion 35 and the bottom plate portion 36, respectively. These nozzles 33, 33, ..., 34 are passages that have the function of allowing fresh air supplied from the intake port 13 to the main chamber C1 to flow into the sub-chamber C2, and the function of ejecting the flame generated in the sub-chamber C2 as a torch flame into the main chamber C1 by igniting the spark plug 40 while fresh air has flowed into the sub-chamber C2.

[0034] More specifically, nozzles 33, 33, ... are provided at equal angular intervals in the circumferential direction at four locations along the tapered section 35, and a nozzle 34 is provided at one location in the center of the bottom plate section 36.

[0035] The nozzle 34 provided in the bottom plate portion 36 penetrates the bottom plate portion 36 in a direction perpendicular to the extending direction of the bottom plate portion 36.

[0036] The nozzles 33, 33, ... provided in the tapered section 35 are shaped such that when fresh air flows from the main chamber C1 to the sub-chamber C2 through the nozzles 33, 33, ... a swirling flow of fresh air is generated in the sub-chamber C2. This shape can be defined by the direction of extension of the central axis of the nozzles 33, 33, ... (see the dashed line in Figure 2(b)). Specifically, the central axis of the nozzles 33, 33, ... extends along the tangential direction to the outer edge of the tip 32 when viewed from a direction along the central axis of the tip 32 (as shown in Figure 2(a)), and points towards the vicinity of the electrodes 44, 45 of the spark plug 40 from the main chamber C1 side to the sub-chamber C2 side when viewed from a direction perpendicular to the central axis of the tip 32 (as shown in Figure 2(b)). The value of the inclination angle is not limited to those described above and can be set appropriately with an upper limit of 60° and a lower limit of 0°.

[0037] Furthermore, in order to improve combustion efficiency and obtain the full performance of the engine 10, the ratio of the volume of the sub-chamber C2 to the total opening area of ​​the nozzles 33, 33, ..., 34 must be within a predetermined range. For this reason, the opening area of ​​each nozzle 33, 33, ..., 34 is designed according to the volume of the sub-chamber C2 to satisfy this condition. In this case, the opening areas of the nozzles 33, 33, ... provided in the tapered section 35 and the opening area of ​​the nozzle 34 provided in the bottom plate section 36 may be the same or may be different from each other.

[0038] As described above, the tip 32 of the torch sleeve 30 is equipped with a tapered portion 35, and multiple nozzles 33, 33, ... are provided in this tapered portion 35, which shortens the distance between these nozzles 33, 33, ... and the combustion gas residual region around the tip of the spark plug 40 (for example, the combustion gas residual region such as the insulator pocket between the insulator of the central electrode 44 of the spark plug 40 and the metal shell) (see distance T1 in Figure 3(a) where the shape of the sub-chamber C2 is shown by a dashed line: in Figure 3(a), only one nozzle 33 out of the multiple nozzles 33, 33, ... is shown as a representative). Therefore, the flow velocity of fresh air flowing from the nozzles 33, 33, ... into the sub-chamber C2 can be maintained at a high level, and the fresh air can reach the combustion gas residual region. In addition, the inner diameter of the sub-chamber C2 can be reduced (making the flow of fresh air in the sub-chamber C2 more compact), which makes it easier for the fresh air to reach the combustion gas residual region. These effects make it possible to effectively scavenge combustion gases remaining in the combustion gas residue area, thereby suppressing pre-ignition.

[0039] Furthermore, as mentioned above, by defining the inclination angle of the central axis of the nozzles 33, 33, ..., the direction of the swirling flow of fresh air flowing through the sub-chamber C2 can be made closer to the transverse vortex direction (swirl flow) rather than the longitudinal vortex direction (tumble flow), as shown by the solid arrows in Figure 3(b). This also allows the fresh air to easily reach the combustion gas residual region. In addition, the electrodes 44, 45 of the spark plug 40 are close to the opening positions of the nozzles 33, 33, ... (the positions of the openings facing the sub-chamber C2), and the positions of adjacent nozzles 33, 33 in the circumferential direction of the sub-chamber C2 are also close, which reduces the variation in the torch flame ejected from each nozzle 33, 33, ... into the main chamber C1. Furthermore, after ignition by the spark plug 40, the swirling flow generated in the sub-chamber C2 accelerates combustion in the sub-chamber C2, increasing the penetrating force of the torch flame ejected into the main chamber C1. This also reduces the variation in the torch flame ejected from each nozzle 33, 33, ... toward the main chamber C1. These effects enable uniform combustion throughout the main chamber C1, thereby suppressing knocking of the engine 10.

[0040] As mentioned above, in this embodiment, the spark plug 40 is housed inside the torch sleeve 30, and the space between the tip of the torch sleeve 30 and the tip of the spark plug 40 forms a sub-chamber C2. The spark plug 40 is attached to the torch sleeve 30 by screwing a male thread 41, provided on the outer circumference near the tip of the spark plug 40, into a female thread 31, provided on the inner circumference near the tip of the torch sleeve 30. Therefore, if electrode wear occurs on the spark plug 40 due to long-term use, the spark plug 40 can be removed from the torch sleeve 30 and a new spark plug 40 can be installed. In other words, it is not necessary to replace the entire sub-chamber spark plug 20. This improves maintainability and reduces running costs. Also, if it is necessary to check the electrode wear status of the spark plug 40, the check can be performed by removing the spark plug 40 from the torch sleeve 30. In other words, it is not necessary to remove the entire sub-chamber spark plug 20 from the engine 10 for checks. Therefore, it is possible to improve maintainability and shorten the time required for maintenance work. In the aforementioned Patent Documents 1 and 2, the entire sub-chamber spark plug has a single integrated structure, and if electrode wear occurs, the entire sub-chamber spark plug must be replaced, resulting in high running costs. Furthermore, these Patent Documents could not meet the demand for checking the electrode wear status. The sub-chamber spark plug 20 according to this embodiment can obtain effects and advantages that could not be obtained with the Patent Documents.

[0041] Furthermore, in this embodiment, the inclination direction of the nozzles 33, 33, ... when viewed from a direction along the central axis of the tip portion 32 is opposite to the direction of the intake air swirl formed in the main chamber C1 by the intake port 13.

[0042] Figure 4 is a view of the main chamber C1 from the piston 12 side in this embodiment. In Figure 4, the direction of the swirl of intake air introduced into the main chamber C1 from each intake port 13, 13 is clockwise in the figure. In contrast, the inclination direction of the nozzles 33, 33, ... (the inclination direction toward the main chamber C1) is in the opposite direction to this intake air swirl, that is, counterclockwise in the figure (see Figure 2(a)).

[0043] In an engine 10 that does not have a fuel supply system to the sub-chamber C2 other than the nozzles, there is a concern that the combustion speed in the main chamber C1 will be low because the temperature of the torch flame ejected into the main chamber C1 is relatively low, the amount of the torch flame is relatively small, and the penetrating force of the torch flame is relatively small. In this case, if the intake air (mixture) between adjacent torch flames ejected from each of the multiple nozzles 33, 33, ... can be combusted early, the ratio of the surface area to the volume of the already burned region can be reduced, and the temperature near the flame surface can be kept high, thereby maintaining a high combustion speed in the main chamber C1. In view of this, in this embodiment, by setting the direction of the torch flame ejected into the main chamber C1 and the direction of the intake swirl in opposite directions, the torch flame is not allowed to develop radially (towards the cylinder wall) but to develop circumferentially, and the intake air between adjacent torch flames is ignited early, thereby making it possible to maintain a high combustion rate in the main chamber C1.

[0044] Furthermore, in this embodiment, the tip 32 of the torch sleeve 30 starts from the bottom surface of the cylinder head 15. This reduces the area of ​​the portion of the torch sleeve 30 that faces the main chamber C1. In other words, the heat-receiving area of ​​the torch sleeve 30 from the combustion gas in the main chamber C1 can be reduced. As a result, the temperature rise of the torch sleeve 30 can be suppressed, the temperature rise of the fresh air in the sub-chamber C2 can be suppressed, and pre-ignition can be suppressed.

[0045] -A modified example of a sub-chamber spark plug- Next, a modified example of the sub-chamber ignition plug 20 will be described. In this modified example, the shape of the tip portion 32 of the torch sleeve 30 differs from that of the previously described embodiment. The other configurations and functions are the same as those of the above embodiment, so here we will mainly describe the differences from the above embodiment.

[0046] Figure 5 shows the main parts of the sub-chamber spark plug 20 in this modified example, where Figure 5(a) is a bottom view of the sub-chamber spark plug 20, Figure 5(b) is a cross-sectional view along line BB in Figure 5(a), and Figure 5(c) is a cross-sectional view along line CC in Figure 5(a).

[0047] As shown in Figures 5(b) and 5(c), the tip portion 32 of the torch sleeve 30 has a tapered shape where the part protruding from the cylinder head 15 (the part facing the main chamber C1) bulges out toward the piston 12, and multiple nozzles 33, 33, ..., 34 are provided on this tapered portion (tip portion 32).

[0048] Specifically, the tip portion 32 of the torch sleeve 30 is configured to include a base plate portion 36 extending in a direction perpendicular to the central axis of the torch sleeve 30, and a tapered portion 37 with a circular arc cross-section that smoothly connects the base plate portion 36 and the side wall 38 of the torch sleeve 30.

[0049] In this modified example as well, nozzles 33, 33, ..., 34 are provided at the tip 32 of the torch sleeve 30. These nozzles 33, 33, ..., 34 are composed of through holes provided in the tapered portion 37 and the bottom plate portion 36, respectively.

[0050] The nozzle 34 provided in the bottom plate portion 36 penetrates the bottom plate portion 36 in a direction perpendicular to the extending direction of the bottom plate portion 36.

[0051] The nozzles 33, 33, ... provided in the tapered section 37 are shaped such that when fresh air flows from the main chamber C1 to the sub-chamber C2 through these nozzles 33, 33, ... a swirling flow of fresh air is generated in the sub-chamber C2. This shape can also be defined by the direction of extension of the central axis of the nozzles 33, 33, .... The direction of extension of the central axis of these nozzles 33, 33, ... is the same as that of the embodiment described above, so its explanation is omitted here.

[0052] This modified version can achieve the same effects as the embodiment described above. In other words, the distance between the nozzles 33, 33, ... of the torch sleeve 30 and the combustion gas residue area around the tip of the spark plug 40 can be shortened (see distance T2 in Figure 6(a), which shows the shape of the sub-chamber C2 with a dashed line: Figure 6(a) also shows only one nozzle 33 out of the multiple nozzles 33, 33, ... as a representative example). As a result, fresh air can easily reach the combustion gas residue area, making it possible to effectively scavenge the combustion gases remaining in the combustion gas residue area and suppress pre-ignition.

[0053] Furthermore, by defining the inclination angle of the central axis of the nozzles 33, 33, ..., as in the previously described embodiment, the direction of the swirling flow of fresh air flowing through the sub-chamber C2 can be made to be close to the direction of a transverse vortex (swirl flow), as shown by the solid arrow in Figure 6(b). This also effectively scavenges the residual combustion gas region and reduces the variation in the torch flame ejected from each nozzle 33, 33, ... into the main chamber C1. In addition, combustion can be carried out uniformly throughout the main chamber C1, and knocking of the engine 10 can be suppressed.

[0054] Furthermore, in this modified example, as shown in Figure 4, the inclination direction of the nozzles 33, 33, ... when viewed from a direction along the central axis of the tip portion 32 is opposite to the direction of the intake air swirl formed in the main chamber C1 by the intake port 13. Therefore, similar to the embodiment described above, it is possible to maintain a high combustion rate in the main chamber C1 by developing the torch flame in the circumferential direction and burning the intake air between adjacent torch flames early.

[0055] Furthermore, in this modified example as well, the tip 32 of the torch sleeve 30 starts from the bottom surface of the cylinder head 15. This suppresses the temperature rise of the torch sleeve 30, which in turn suppresses the temperature rise of the fresh air in the sub-chamber C2, thereby suppressing pre-ignition.

[0056] -Comparison with comparative examples- Next, a comparison will be made between the sub-chamber ignition plug 20 according to the above-described embodiment and the sub-chamber ignition plug 20 according to a modified example, and the sub-chamber ignition plug according to a comparative example in which the tip portion 32 of the torch sleeve 30 does not have a tapered portion 35 or a narrowing portion 37.

[0057] Figure 7 shows the main parts of the sub-chamber spark plug a in the comparative example, where Figure 7(a) is a bottom view of the sub-chamber spark plug a, Figure 7(b) is a cross-sectional view along line BB in Figure 7(a), and Figure 7(c) is a cross-sectional view along line CC in Figure 7(a).

[0058] As shown in Figures 7(b) and 7(c), the sub-chamber ignition plug a in the comparative example does not have a tapered portion 35 like in the embodiment or a tapered portion 37 like in the modified example, and the tip portion c of the torch sleeve b is composed of a side wall d and a bottom plate portion e.

[0059] With the configuration of this comparative example, the distance between the nozzles f,f,… of the torch sleeve b and the combustion gas residual region around the tip of the spark plug g cannot be shortened (see distance T3 in Figure 8(a) where the shape of the sub-chamber C2 is shown by a dashed line), making it difficult to bring fresh air to the combustion gas residual region, and potentially causing pre-ignition due to the inability to scavenge the combustion gases remaining in the combustion gas residual region.

[0060] Furthermore, the direction of the swirling flow of fresh air through the sub-chamber C2 is close to the longitudinal vortex direction (tumble flow), as shown by the solid arrow in Figure 8(b). This makes it difficult to get the fresh air to reach the combustion gas residue region, preventing the scavenging of combustion gases remaining in that region. It also increases the possibility of large variations in the torch flames ejected into the main chamber from each nozzle f,f,.... In addition, it becomes difficult to achieve uniform combustion throughout the main chamber, which may lead to engine knocking.

[0061] In the embodiments and modifications described above, it is possible to eliminate all of these problems.

[0062] The inventors of the present invention conducted simulations to confirm the effects of the above embodiments and modified examples.

[0063] First, a simulation was performed on the shape of the torch flame ejected from the sub-chamber C2 into the main chamber C1. Figure 9 shows the simulation results of the shape of the torch flame when the main chamber C1 is viewed from the piston side, with Figure 9(a) showing the case of the embodiment, Figure 9(b) showing the case of the modified example, and Figure 9(c) showing the case of the comparative example. As is clear from these figures, the torch flame ejected from the sub-chamber C2 into the main chamber C1 is larger in the embodiment and the modified example compared to the comparative example (see flames F1, F2, and F3 in each figure), confirming that efficient combustion is occurring.

[0064] In addition, another simulation was performed to simulate the amount of carbon dioxide in the sub-chamber C2 during the period from the intake stroke to the compression stroke of the engine 10. Figure 10 shows the simulation results of the amount of carbon dioxide in the sub-chamber during the period from the intake stroke to the compression stroke of the engine in each of the embodiments, modified examples, and comparative examples. In Figure 10, BDC is the timing when the piston 12 reaches the intake bottom dead center, and TDC is the timing when the piston 12 reaches the compression top dead center. As is clear from this figure, the amount of carbon dioxide in the sub-chamber is lower in the embodiments and modified examples compared to the comparative examples. In other words, it was confirmed that scavenging in the sub-chamber was being performed effectively.

[0065] -Other Embodiments- Furthermore, the present invention is not limited to the embodiments and modifications described above, and all modifications and applications encompassed within the scope of the claims and equivalents thereof are possible.

[0066] For example, the above embodiments and modifications describe the application of the present invention to a hydrogen engine. However, the present invention is not limited to this and can also be applied to other engines equipped with a sub-chamber spark plug 20.

[0067] Furthermore, the above embodiments and modifications describe the case in which nozzles 33, 33, ... are provided at four locations on the tapered portion 35 or the narrowing portion 37. The number of nozzles 33, 33, ... in the present invention is not limited to this, and may be three or fewer, or five or more. However, as mentioned above, it is necessary to design the opening area of ​​each nozzle 33, 33, ..., 34 such that the ratio of the volume of the sub-chamber C2 to the total opening area of ​​the nozzles 33, 33, ..., 34 is within a predetermined range.

[0068] Furthermore, in the above-described embodiment and its modifications, the inclination direction of the nozzles 33, 33, ... when viewed from a direction along the central axis of the tip portion 32 was opposite to the direction of the intake air swirl formed in the main chamber C1 by the intake port 13. The present invention is not limited to this, and the inclination direction of the nozzles 33, 33, ... when viewed from a direction along the central axis of the tip portion 32 may be the same direction as the intake air swirl formed in the main chamber C1 by the intake port 13. This configuration is effective when the temperature of the torch flame ejected into the main chamber C1 is relatively high, the amount of the torch flame is relatively large, and the penetrating force of the torch flame is relatively large. In other words, by making the direction of the torch flame ejected into the main chamber C1 the same as the direction of the intake air swirl, the torch flame can be rapidly diffused over a wide area by utilizing this swirl, thereby making it possible to obtain a high combustion speed in the main chamber C1. [Industrial applicability]

[0069] The present invention is applicable to engines equipped with a sub-chamber spark plug. [Explanation of Symbols]

[0070] 10 Engines 12 pistons 13 Intake Ports 15 Cylinder head 20 Sub-chamber spark plug 30 Torch Sleeves 32 Tip 33 spout 35 Tapered section 37. Tapered section 40 Spark plugs 44 Center electrode 45 Ground electrode C1 Main room C2 Antechamber

Claims

1. An engine equipped with a pre-chamber spark plug, A torch sleeve, which is mounted on the cylinder head and has a nozzle, and a spark plug form a sub-chamber. The engine is characterized in that the torch sleeve has a tapered shape at the tip that protrudes from the cylinder head, with the diameter decreasing towards the piston, and the nozzle is provided at the tapered portion.

2. In the engine according to claim 1, The engine is characterized in that the tapered portion of the torch sleeve is tapered.

3. In the engine according to claim 1 or 2, The central axis of the aforementioned nozzle is, When viewed from a direction along the central axis of the tapered portion, the tapered portion is inclined within an angular range of up to 60° with respect to the tangential direction to the outer edge of the tapered portion, from the main chamber side of the engine toward the sub-chamber side, An engine characterized in that, when viewed from a direction perpendicular to the central axis of the tapered portion, it is directed from the main chamber side towards the vicinity of the spark plug electrode.

4. In the engine according to claim 3, An engine characterized in that the direction of the torch flame ejected from the sub-chamber into the main chamber by the nozzle is opposite to the direction of the intake swirl formed in the main chamber by the intake port of the engine.

5. In the engine according to claim 3, An engine characterized in that the direction of the torch flame ejected from the sub-chamber into the main chamber by the nozzle is the same direction as the intake swirl formed in the main chamber by the intake port of the engine.

6. In the engine according to claim 1 or 2, The engine is characterized in that the tapered portion of the torch sleeve begins from the bottom surface of the cylinder head.

Images