JP2008151000A - Internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cylinder injection type spark ignition internal combustion engine capable of stratified combustion by restraining generation of an over-lean air-fuel mixture. <P>SOLUTION: A fuel injection valve 55 and a first spark plug 51 are arranged in a ceiling wall central part 22a of a combustion chamber 40, and a second spark plug 52 is arranged in a ceiling wall peripheral edge part 22c. The fuel injection valve 55 respectively injects fuel in the direction turning to an electrode 51a of the first spark plug 51 and the direction turning to a cavity 44 of a piston 30. The cavity 44 of the piston 30 receives and introduces fuel from the fuel injection valve 55 to an electrode 52a of the second spark plug 51 existing in the ceiling wall peripheral edge part 22c. A stratified air-fuel mixture is respectively and separately formed in the vicinity of the first spark plug 51 and the second spark plug 52. Generation of the over-lean air-fuel mixture by diffusion of an outside part of the stratified air-fuel mixture, is restrained by colliding the mutual stratified air-fuel mixtures expanding by igniting. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an in-cylinder spark ignition internal combustion engine, and more particularly to an internal combustion engine capable of stratified combustion.

  In a cylinder-injected spark ignition internal combustion engine, in order to improve fuel efficiency, a layered mixture (hereinafter referred to as a stratified mixture) is formed around the spark discharge part of the spark plug and burned. It is known to perform so-called stratified combustion. Conventionally, an air guide type, a spray guide type, a wall guide type, and the like are known as a method for forming a stratified mixture in the vicinity of a spark plug.

  In the spray guide type, fuel is injected toward the spark discharge portion of the spark plug to form a layered mixture by fuel spray in the spark discharge portion of the spark plug. In addition, the air guide type further utilizes the in-cylinder gas flow such as squish to lead a low penetrating fuel spray to the spark discharge portion of the spark plug, thereby forming a stratified mixture. On the other hand, in the wall guide type, fuel spray having a high penetrating force is guided along the cavity wall on the piston top surface to the spark discharge portion of the spark plug, thereby forming a stratified mixture.

  As an internal combustion engine capable of stratified combustion by forming a stratified mixture in the spark discharge portion of the spark plug as described above, for example, there is one described in Patent Document 1 below. In the technique described in Patent Document 1, fuel is injected toward the cavity of the piston, and the injected fuel is reflected by the cavity wall inclined toward the spark plug to form a stratified mixture at the spark discharge portion of the spark plug. is doing. The squish flow generated in the compression stroke prevents the stratified mixture formed in the spark discharge portion of the spark plug from diffusing.

JP-A-11-182247

  A stratified mixture ignited by a spark plug is ignited by a flame as it propagates from the ignition point and expands by combustion. By this expansion, the outer portion of the stratified gas mixture that has not been ignited is pushed and diffused toward the cylinder wall. In this process of expansion of the stratified mixture, the outer part of the stratified mixture becomes more dilute by diffusing, and a super lean mixture (hereinafter referred to as the flammability limit) exceeding the flame propagation limit (flammable limit). May be referred to as an over lean mixture).

  Such over-lean air-fuel mixture is discharged from the cylinder together with the burned gas without burning. For this reason, when an overlean air-fuel mixture is generated, there arises a problem that unburned hydrocarbon (HC) in the exhaust gas increases. Further, there is a problem that heat generation in the internal combustion engine is reduced and thermal efficiency is lowered by the amount of unburned hydrocarbons.

  The present invention has been made in view of the above, and an object of the present invention is to provide an in-cylinder spark ignition internal combustion engine capable of performing stratified combustion by suppressing the generation of an over-lean mixture as much as possible.

  In order to achieve the above object, an internal combustion engine according to the present invention is an internal combustion engine capable of stratified combustion in a combustion chamber, and includes a first spark plug provided in a central portion of a ceiling wall of the combustion chamber, a combustion chamber A second spark plug provided at the peripheral edge of the ceiling wall, a fuel injection device provided at the center of the ceiling wall of the combustion chamber and capable of directly injecting fuel in two directions in the combustion chamber, and fuel from the fuel injection device And a piston provided with a cavity that can be guided to the spark discharge part of the second spark plug, and the fuel injection device is directed to the spark discharge part of the first spark plug and to the cavity The fuel is injected respectively. A fuel injection valve at the center of the ceiling wall injects fuel toward the spark discharge portion of the first spark plug, also at the center of the ceiling wall, and injects fuel toward the piston cavity. The cavity of the piston receives the fuel from the fuel injection valve and guides it to the spark discharge part of the second spark plug at the peripheral part of the ceiling wall.

  In the internal combustion engine according to the present invention, the cavity wall that defines the shape of the cavity has one edge portion facing the nozzle portion of the fuel injection device, and the other edge portion serving as a spark discharge portion of the second spark plug. It can be the opposite.

  In the internal combustion engine according to the present invention, the second spark plug may be provided at a portion on the exhaust side of the peripheral edge of the ceiling wall of the combustion chamber.

  In the internal combustion engine according to the present invention, the second spark plug may be provided in a portion sandwiched between the outer edge of the intake port and the outer edge of the exhaust port in the periphery of the ceiling wall of the combustion chamber.

  In the internal combustion engine according to the present invention, the fuel injection device may be composed of one fuel injection valve, and fuel is injected into the fuel injection valve toward the spark discharge portion of the first spark plug. The first injection hole and the second injection hole for injecting fuel toward one edge of the cavity wall of the piston can be provided. From the first injection hole and the second injection hole, At the same time, fuel can be injected.

  In the internal combustion engine according to the present invention, the second nozzle hole may have a nozzle hole shape set so that the tip speed of the injected fuel spray is larger than that of the first nozzle hole.

  In the internal combustion engine according to the present invention, the second nozzle hole may have a larger L / D ratio, which is a ratio between the nozzle hole length and the nozzle hole diameter, as compared with the first nozzle hole.

  In the internal combustion engine according to the present invention, a squish flow generating means for generating a squish flow toward the first spark plug is provided on the opposite side of the periphery of the ceiling wall of the combustion chamber to the side where the second spark plug is provided. Can be.

  In the internal combustion engine according to the present invention, the squish flow generating means is a combustion chamber side surface of an intake valve or an exhaust valve and a piston top surface formed so that a portion facing the surface is parallel to the surface. Can be.

  According to the present invention, the fuel injection valve at the center of the ceiling wall injects fuel toward the spark discharge portion of the first spark plug, which is also at the center of the ceiling wall, and injects fuel toward the cavity of the piston. To do. Since the cavity of the piston guides the fuel from the fuel injection valve to the spark discharge part of the second spark plug at the peripheral part of the ceiling wall, the vicinity of the spark discharge part of the first spark plug and the second spark plug A separate stratified mixture can be formed in the vicinity of the spark discharge portion. The stratified mixture is ignited by the first and second spark plugs, and the expanding stratified mixture collides with each other, so that the unburned portion outside the stratified mixture suppresses diffusion, and this outer portion It is possible to suppress the occurrence of an over lean mixture.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art or those that are substantially the same.

  First, the configuration of the internal combustion engine according to the present embodiment will be described with reference to FIGS. FIG. 1 is a cross-sectional view showing a configuration around a cylinder of an internal combustion engine. FIG. 2 is a diagram showing a positional relationship among the fuel injection valve, the spark plug, and the intake / exhaust valve, and is a diagram of the cylinder head viewed from the piston side. FIG. 3 is a view showing the positional relationship between the cavity formed in the piston, the fuel injection valve, and the spark plug, and is a view of the piston top surface as viewed from the cylinder head side. 1 to 3 schematically show only main parts related to the present invention.

  The internal combustion engine according to this embodiment is an in-cylinder injection type gasoline engine in which a fuel injection valve directly injects fuel (gasoline) into a cylinder, and an air-fuel mixture formed in the cylinder is ignited by an ignition plug. It is a spark ignition engine. In the present embodiment, the internal combustion engine 10 is provided with an electronic control device (hereinafter referred to as ECU) (not shown) as means for controlling the fuel injection valve and the spark plug. Hereinafter, one cylinder among the plurality of cylinders of the internal combustion engine will be described.

  As shown in FIG. 1, the internal combustion engine 10 is provided with a cylinder block 12, a cylinder head 20, a piston 30, and a connecting rod and a crankshaft (not shown) as parts of an engine body system in which a cylinder is formed. ing. A cylinder bore 14 is formed in the cylinder block 12, and the piston 30 reciprocates in the cylinder bore 14 along its axis (hereinafter referred to as a bore axis and indicated by a one-dot chain line C).

  In the following description, the direction along the axis C of the cylinder bore 14 is referred to as “bore axial direction”. In the bore axis direction, the direction in which the piston 30 compresses the gas in the cylinder is referred to as “upward”, and is indicated by an arrow U in the drawing. Further, the direction opposite to the upper direction is described as “lower”, and is indicated by an arrow D in the figure. Further, it is a direction orthogonal to the bore axis C, and the radial direction of the cylinder bore 14 is referred to as “bore radial direction” and is indicated by an arrow R in the figure.

  A cylinder head 20 is coupled to the cylinder block 12 so as to face the piston 30 and close the cylinder bore 14. Hereinafter, a plane serving as a mating surface between the cylinder block 12 and the cylinder head 20 is referred to as a “top deck plane” and is indicated by a two-dot chain line T in the drawing. The top deck plane T is orthogonal to the bore axis C.

  A pent roof type combustion chamber 40 is formed in the cylinder head 20. Specifically, the wall surface 22 (hereinafter referred to as a ceiling wall) of the cylinder head 20 that defines the shape of the combustion chamber 40 has a bore radial direction R from the center of the combustion chamber 40, that is, the bore axis C (in the drawing). , Indicated by the symbol IN) or the exhaust side (indicated by the symbol EX in the figure), the distance from the top deck plane T decreases. The ceiling wall 22 is formed on the peripheral edge 40e of the combustion chamber 40 so as to be smoothly continuous with the wall surface 15 of the cylinder bore 14 (hereinafter referred to as a cylinder wall).

  The piston 30 is provided with a plurality of piston rings 37, 38 and 39. When the piston 30 reciprocates, the piston rings 37, 38, 39 are in sliding contact with the cylinder wall 15, thereby maintaining airtightness between the combustion chamber 40 and a crankcase (not shown). The piston ring closest to the cylinder head 20 is referred to as a “top ring”. Above the top ring 37, a clevis volume 43, which is a gap between the cylinder wall 15 and the side wall 30e of the piston 30, is formed.

  The reciprocating motion of the piston 30 is converted into a rotational motion and output from a crankshaft (not shown). The internal combustion engine 10 is provided with a crank angle sensor (not shown) that detects a rotation angle position of the crankshaft (hereinafter referred to as a crank angle), and sends a signal related to the crank angle to the ECU. .

  Further, the piston 30 is formed with a cavity 44 that is a space that is recessed downward D in the bore axis direction. In other words, a curved wall surface 33 (hereinafter referred to as a cavity wall) that defines the shape of the cavity 44 is formed on the top surface 32 of the piston 30. Detailed shapes of the cavity 44 and the cavity wall 33 will be described later.

  The space surrounded by the cylinder wall 15 of the cylinder block 12, the ceiling wall 22 of the cylinder head 20, and the top surface 32 (including the cavity wall 33) of the piston 30 described above is a so-called “cylinder”. The cylinder includes a combustion chamber 40 formed in the cylinder head 20 and a cavity 44 formed in the piston 30.

  Further, as shown in FIG. 1, the cylinder head 20 has an intake port 24 for guiding intake air to the combustion chamber 40 on one side of the bore axis C, and on the other side. Is formed with an exhaust port 26 for exhausting exhaust gas from the combustion chamber 40.

  The cylinder head 20 is provided with an intake valve 25 and an exhaust valve 27 corresponding to the intake port 24 and the exhaust port 26, respectively. The intake valve 25 and the exhaust valve 27 are driven by receiving mechanical power from the crankshaft via a camshaft. The intake valve 25 and the exhaust valve 27 are configured to be openable and closable at a predetermined timing according to the rotation angle position of the crankshaft (hereinafter referred to as the crank angle).

  When the intake valve 25 is opened, the intake port 24 and the combustion chamber 40 communicate with each other, and air from an intake passage (not shown) can be taken into the combustion chamber 40 in the cylinder from the intake port. When the exhaust valve 27 is opened, the exhaust port 26 and the combustion chamber 40 communicate with each other, and the exhaust gas in the combustion chamber 40 in the cylinder can be discharged from the exhaust port 26 to an exhaust passage (not shown).

  As shown in FIG. 2, two intake ports 24 and two exhaust ports 26 are provided, each including a cylinder bore axis C and a virtual plane (one point in the figure) extending in the axial direction of a crankshaft (not shown). They are arranged so as to oppose each other across a chain line L). That is, in each cylinder, the intake port 24 and the exhaust port 26 have a so-called cross flow arrangement.

  In the following description, the side on which the intake port 24 is provided with respect to the plane L including the bore axis C is referred to as the intake side, and is indicated by the symbol IN in the drawing. On the other hand, the side on which the exhaust port 26 is provided with respect to the plane L is referred to as the exhaust side, and is indicated by the symbol EX in the figure.

  As shown in FIG. 1, the cylinder head 20 is provided with two spark plugs 51 and 52 as an ignition device for igniting a stratified mixture (including fuel spray) formed in the cylinder. These first and second spark plugs 51 and 52 have electrodes 51a and 52a as spark discharge portions for generating ignition sparks. The first and second spark plugs 51 and 52 are arranged so that these electrodes 51 a and 52 a protrude into the combustion chamber 40.

  As shown in FIGS. 1 and 2, the first spark plug 51 is provided in the center portion 22 a of the ceiling wall of the combustion chamber 40 formed in the cylinder head 20. Specifically, the first spark plug 51 is disposed on the exhaust side from the plane L including the axis C in the center portion 22 a of the ceiling wall, and the electrode 51 a protrudes toward the center of the combustion chamber 40. .

  On the other hand, the second spark plug 52 is provided on the ceiling wall peripheral part 22 c of the combustion chamber 40 formed in the cylinder head 20. Specifically, the second spark plug 52 is disposed at a portion on the exhaust side of the ceiling wall peripheral portion 22 c, that is, a portion sandwiched between the peripheral edge 22 e of the ceiling wall 22 and the outer edge 26 e of the two exhaust ports 26. The electrode 52a protrudes to the exhaust side of the peripheral edge portion 40c of the combustion chamber 40.

  As shown in FIG. 2, the “ceiling wall central portion” 22 a includes a portion of the ceiling wall 22 of the combustion chamber 40 through which the bore axis C passes, and the outer edge 24 e of the intake port 24 and the outer edge of the exhaust port 26. 26e. On the other hand, the “ceiling wall peripheral portion” 22c is a portion including the peripheral edge 40e of the combustion chamber 40, that is, the peripheral edge 22e of the ceiling wall 22, and the peripheral edge 22e of the ceiling wall 22 and the outer edge 24e of the intake port 24 or the exhaust port 26. This is a portion sandwiched between the outer edge 26e.

  The first and second spark plugs 51 and 52 receive supply of secondary current from an ignition coil (not shown), respectively, and generate sparks at the electrodes 51a and 52a serving as spark discharge portions. The stratified mixture (including fuel spray) formed in the combustion chamber 40 in the cylinder by this ignition spark ignites and starts combustion. The ignition timing at which the first and second spark plugs 51 and 52 generate an ignition spark is controlled by the ECU.

  Further, as shown in FIG. 1, the cylinder head 20 is provided with one fuel injection valve 55 as a fuel injection device that directly injects fuel into the cylinder, that is, the combustion chamber 40. The fuel injection valve 55 is an electromagnetically driven injection valve having a substantially cylindrical shape, and has a nozzle portion 55a provided with a plurality of injection holes. The fuel injection valve 55 is disposed so that the nozzle portion 55 a protrudes into the combustion chamber 40. The fuel injection valve 55 is disposed on the intake side of the center portion 22a of the ceiling wall so as to face the first spark plug 51 with the bore axis C interposed therebetween. The fuel injection valve 55 is disposed with its axis (indicated by a one-dot chain line J in the figure) inclined at a predetermined angle with respect to the bore axis C so that the nozzle portion 55a faces the exhaust side. Yes.

  The fuel injection valve 55 is supplied with fuel at a predetermined fuel pressure from a fuel rail (not shown). The valve opening period during which the fuel injection valve 55 opens and injects fuel, that is, the valve opening timing and the valve opening time length are controlled by an ECU (not shown).

  A plurality of nozzle holes (not shown) are formed in the nozzle portion 55 a of the fuel injection valve 55, and each nozzle hole is exposed to the combustion chamber 40. The fuel injected from these nozzle holes flows in the combustion chamber 40 as a fuel spray lump (cloud). In the flow process, the fuel spray is mixed with the surrounding air to form a layered mixture (hereinafter referred to as a stratified mixture).

  In the fuel injection valve 55 according to the present embodiment, two nozzle holes 63 and 64 (a first nozzle hole 63 and a second nozzle hole 64) are formed in the nozzle portion 55a. Hereinafter, the details of the nozzle hole of the fuel injection valve will be described with reference to FIG. FIG. 4 is a diagram for explaining the relationship between the L / D ratio of the first and second nozzle holes and the fuel spray. FIG. 4A is a view from the nozzle hole (second nozzle) having a large L / D ratio. It is a figure which shows the aspect of injected fuel, (b) is a figure which shows the aspect of the injected fuel from a nozzle hole (1st nozzle hole) with a small L / D ratio.

  As shown in FIG. 4, a first injection hole 63 and a second injection hole 64 having different injection hole shapes are formed in the nozzle portion 55 a of the fuel injection valve 55. In the figure, reference numerals L1 and L2 indicate the nozzle hole length, and reference numerals D1 and D2 indicate the nozzle hole diameter. The nozzle hole length L2 of the second nozzle hole 64 is set to be larger than the nozzle hole length of the first nozzle hole 63. The nozzle hole diameter D2 of the second nozzle hole 64 is set to be smaller than the nozzle hole diameter D1 of the first nozzle hole 63. That is, the L / D ratio, which is the ratio between the nozzle hole length L and the nozzle hole diameter D, is set larger than that of the first nozzle hole 63 in the second nozzle hole 64.

  When the L / D ratio of the injection hole is set to be large, as shown in FIG. 4A, the injection angle β is decreased and the velocity V2 of the injected fuel is increased. Thereby, the fuel spray immediately after injection becomes a long and narrow shape, and the flow velocity also increases. On the other hand, when the L / D ratio of the injection hole is set small, as shown in FIG. 4B, the injection angle α increases and the injected fuel speed V1 decreases. As a result, the fuel spray immediately after the injection has a thick and short shape due to the diffusion of the fuel, and its flow rate is reduced.

  Since the second injection hole 64 has a larger L / D ratio than the first injection hole 63, the spray angle is smaller than that of the first injection hole 63 and the flow rate of the injected fuel spray is high. Can be large. In this way, the flow of the fuel spray from the first injection hole 63 and the L / D ratio of the second injection hole 64 are set larger than the L / D ratio of the first injection hole 63, so that the second The flow rate of the fuel spray injected from the injection hole 64 can be made larger than the flow rate of the fuel spray from the first injection hole 63.

  As a method for changing the flow rate of the fuel spray, there is also a method for changing the flow rate of fuel injected from the nozzle hole. The fuel spray momentum can be increased by setting the internal structure of the fuel injection valve so that the flow rate of fuel injected from the nozzle hole is larger than that of the other nozzle holes. It is good also as what enlarges.

  When the fuel injection valve 55 configured as described above is opened, fuels having different flow speeds are injected from the first injection holes 63 and the second injection holes 64 in different directions, respectively, and the fuels have different flow paths. It is possible to form a spray. These two fuel sprays are each mixed with air in the flow process to form two independent stratified mixtures.

  The fuel injected from the first injection holes 63 forms a first fuel spray lump (hereinafter referred to as a first fuel spray). The first fuel spray flows from the nozzle portion 55 a of the fuel injection valve 55 toward the electrode 51 a of the first spark plug 51. That is, the shape of the first injection hole 63 of the fuel injection valve 55 is set so that the injected first fuel spray is directed toward the first spark plug 51. The first fuel spray flows in the vicinity of the electrode 51a of the first spark plug 51 and is mixed with air to form a first layered mixture (hereinafter referred to as a first stratified mixture). .

  On the other hand, the fuel injected from the second injection holes 64 forms a second fuel spray lump (hereinafter referred to as second fuel spray). The second fuel spray flows from the nozzle portion 55 a of the fuel injection valve 55 toward the cavity 44 of the piston 30. That is, the second injection hole 64 of the fuel injection valve 55 is set so that the injected second fuel spray is directed toward the cavity 44. The second fuel spray is guided to the second spark plug 52 by the cavity 44 and mixed with air to form a second layered mixture (hereinafter referred to as a second stratified mixture).

  In the present embodiment, one nozzle hole has been described as forming one fuel spray lump (cloud), but the method of forming the fuel spray is not limited to this. A single fuel spray lump may be formed by a plurality of nozzle holes.

  In the piston 30, a dish-shaped cavity 44 that receives the second fuel spray from the fuel injection valve 55 is formed from the approximate center of the piston 30 to the exhaust side. As shown in FIG. 3, the cavity wall 33 that defines the shape of the cavity 44 has an edge portion 33 a (hereinafter referred to as a center side edge portion) substantially at the center of the piston 30 facing the nozzle portion 55 a of the fuel injection valve 55. It is formed to do. In addition, the cavity wall 33 has an edge portion 33c (hereinafter referred to as a peripheral edge portion) on the peripheral side of the piston 30 facing the central side edge portion 33a so as to oppose the electrode 52a of the second spark plug 52. Is formed. In other words, the piston 30 is positioned in the cylinder bore 14 so that the peripheral edge 33c faces the exhaust side. As shown in FIG. 1, in the cavity wall 33, the center side edge part 33a and the peripheral side edge part 33c are smoothly continuing.

  The piston 30 can receive the fuel spray flowing from the upper side U to the lower side D at the approximate center of the combustion chamber 40 at the piston central side edge 33 a of the cavity wall 33. In addition, the piston 30 can guide the second fuel spray received at the center side edge portion 33 a to the peripheral edge portion 33 c along the cavity wall 33. That is, the cavity 44 of the piston 30 has a peripheral edge that is the other edge of the fuel spray that has flowed into the cavity 44 from the central edge 33a when moving upward U (when the piston is raised). 33c.

  The piston 30 configured in this manner allows the second fuel spray injected from the fuel injection valve 55 in the central portion 22a of the ceiling wall to be ceiling-suspended by the cavity 44 during the compression stroke of the internal combustion engine 10, that is, when the piston 30 is lifted. It can guide toward the electrode 52a of the second spark plug 52 on the exhaust side of the wall peripheral portion 22c. Thereby, the internal combustion engine 10 can form the second stratified mixture in the vicinity of the electrode 52 a of the second spark plug 52, that is, in the peripheral edge portion 40 c of the combustion chamber 40.

  A squish surface 36 is formed on the intake side of the top surface 32 of the piston 30 in order to generate a squish flow toward the central portion 40a of the combustion chamber 40 (a region through which the bore axis C passes). The squish surface 36 faces the surface 25f of the intake valve 25 on the combustion chamber 40 side (hereinafter referred to as the intake valve surface) and is set to be parallel to the intake valve surface 25f. When the piston 30 moves upward U, the gas between the intake valve surface 25f and the squish surface 36 is compressed, and a squish flow from here toward the central portion 40a of the combustion chamber 40 is generated.

  The ECU receives a signal from the crank angle sensor and detects a rotation angle position of the crankshaft (hereinafter referred to as a crank angle). Based on this crank angle, the rotational speed of the crankshaft of the internal combustion engine 10 (hereinafter referred to as engine rotational speed) is calculated. Further, the ECU receives a signal from an accelerator position sensor (not shown) and detects an output torque required for the internal combustion engine (hereinafter referred to as engine load). Based on the engine speed and the engine load, the ECU determines whether the internal combustion engine 10 performs homogeneous combustion or stratified combustion, and opens the fuel injection valve 55 and the ignition timing of the ignition plug. Is adjusted.

  The internal combustion engine 10 configured as described above performs homogeneous combustion when operating at a high rotational speed or a high load. When performing homogeneous combustion, fuel is injected by the fuel injection valve 55 in the intake stroke, so that the internal combustion engine 10 forms a homogeneous air-fuel mixture in the cylinder from the intake stroke to the compression stroke. The internal combustion engine 10 ignites the first and second spark plugs 51 and 52 simultaneously at an appropriate timing before top dead center. At the time of homogeneous combustion, the internal combustion engine 10 can stabilize the ignition of the mixture and the flame propagation by igniting the in-cylinder mixture with two ignition plugs. Thereby, compared with the internal combustion engine 10 provided with only one spark plug, it can suppress that a fluctuation | variation arises in output torque.

  On the other hand, when operating at a low rotational speed and a low load, the internal combustion engine 10 performs stratified combustion. Hereinafter, the operation when the internal combustion engine 10 according to the present embodiment performs stratified combustion will be described with reference to FIGS. FIG. 5 is a timing chart showing the fuel injection timing and ignition timing during stratified combustion of the internal combustion engine. FIGS. 6-1 to 6-4 are cross-sectional views showing the configuration around the cylinder of the internal combustion engine, and FIG. 6-1 is a view showing the injection angle at the start of fuel injection. FIG. 6B is a diagram illustrating a state where fuel injection is completed and fuel spray is formed. FIG. 6-3 is a diagram illustrating a state in which the fuel spray flows and a stratified mixture is formed in the vicinity of the first and second spark plugs. FIG. 6-4 is a diagram illustrating a state immediately before the stratified mixture ignited by the spark plug expands and the stratified mixtures collide with each other. In FIG. 5, the ignition top dead center (compression top dead center) is indicated by “ITDC”, and the bottom dead center is indicated by “BDC”.

  First, as shown in FIG. 5, the internal combustion engine 10 is controlled by the ECU to open the fuel injection valve 55 at the time T1 of the compression stroke. The fuel injection valve 55 starts fuel injection from the first injection hole 63 and the second injection hole 64 at the same time. As shown in FIG. 5A, the fuel injection valve 55 of the internal combustion engine 10 injects fuel from the first injection hole 63 toward the electrode 51 a of the first spark plug 51 and from the second injection hole 64 to the piston 30. The fuel is injected toward the central side edge 33a of the cavity wall 33 formed in the above.

  In the fuel injection valve 55, the injection angle of fuel injected from the first injection hole 63 (indicated by the angle α in FIG. 6A) is the injection angle of fuel injected from the second injection hole 64 (FIG. 6-1). The angle is wider than the angle β). The time T1, that is, the opening timing of the fuel injection valve 55 is set to be 30 to 50 ° CA before ignition top dead center.

  At time T2, the internal combustion engine 10 is controlled by the ECU to close the fuel injection valve 55. At this time, as shown in FIG. 6B, the fuel injection valve 55 forms a first fuel spray 61 that flows toward the electrode 51a of the first spark plug 51 by the fuel injected from the first injection hole 63. Yes. At the same time, the fuel injection valve 55 forms a second fuel spray 62 that flows toward the cavity 44 of the piston 30 by the fuel injected from the second injection hole 64.

  The second fuel spray 62 injected from the second injection hole 64 has an elongated shape as compared with the first fuel spray 61 injected from the first injection hole 63. The moving speed B of the “tip” of the second fuel spray 62 (hereinafter referred to as the tip speed) is larger than the tip speed A of the first fuel spray 61. Note that the “tip” of the fuel spray means an end on the traveling direction side of the fuel spray moving path.

  The second fuel spray 62 injected from the second injection hole 64 of the fuel injection valve 55 flows toward the cavity 44 at the tip speed B and collides with the central side edge 33 a of the cavity wall 33 of the piston 30. The collided second fuel spray 62 flows along the cavity wall 33 to the other edge 33c on the exhaust side (the flow path is indicated by an arrow G in the figure). Thus, the second fuel spray 62 is guided in the cavity 44 toward the electrode 52 a of the second spark plug 52 by the rising piston 30. On the other hand, the first fuel spray 61 injected from the first injection hole 63 flows toward the exhaust side toward the electrode 51a of the first spark plug 51 by the momentum (penetration force) of the spray itself.

  At the time T3, the first fuel spray 61 is mixed with the surrounding air during the flow, and as shown in FIG. 6-3, the first stratified mixture 71 is formed in the vicinity of the electrode 51a of the first spark plug 51. Is forming. On the other hand, the second fuel spray 62 flowing along the cavity wall 33 is mixed with the surrounding air during the flow, and the second stratification is performed from the peripheral edge 33c of the cavity wall 33 to the electrode 52a of the second spark plug 52. A gas mixture 72 is formed. In FIG. 6C, the outer edges of the first and second stratified mixture 71 and 72 are indicated by broken lines.

  In this way, the internal combustion engine 10 guides the first fuel spray 61 injected from the fuel injection valve 55 to the vicinity of the first spark plug 51 with its penetrating force, that is, with a spray guide, where the first stratification is performed. A gas mixture 71 is formed. In addition, the internal combustion engine 10 guides the second fuel spray 62 injected from the fuel injection valve 55 to the vicinity of the second spark plug 52 along the cavity wall 33, that is, with a wall guide, A two-stratified mixture 72 is formed. Since the portion on the exhaust side of the ceiling wall peripheral portion 22c to which the second fuel spray 62 is guided is a portion having a higher temperature than the intake side, the vaporization of the second fuel spray can be improved.

  At this time T3, the internal combustion engine 10 is controlled by the ECU to ignite the first spark plug 51 and the second spark plug 52 simultaneously. The first and second igniter plugs 51 and 52 are ignited by the sparks generated at the respective electrodes 51a and 52a, and the first and second stratified air-fuel mixtures 71 and 72 are ignited at the center and start to burn. At this time T3, that is, the ignition timing of the first and second spark plugs 51 and 52 is set to be 10 to 20 ° CA before ignition top dead center.

  The first and second stratified air-fuel mixtures 71 and 72 are burned by flame propagation outward from the substantially central portion of the air-fuel mixture. As a result, the first stratified mixture 71 expands from the central portion 40a of the combustion chamber 40 toward the intake side and the exhaust side as shown in FIG. 6-4 (in the drawing, the expansion direction is indicated by the arrows Ei and Ee). ). On the other hand, the second stratified mixture 72 expands from the exhaust side of the peripheral edge portion 40c of the combustion chamber 40 toward the center of the combustion chamber 40 (in the drawing, the expansion direction is indicated by an arrow Ec). In addition, in FIG. 6-4, the outer edge of the 1st and 2nd stratified mixture 71 and 72 is shown with the broken line.

  Then, at the time T4 when the ignition top dead center is 5 to 10 ° CA, the expanding first stratified mixture 71 and the expanded second stratified mixture 72 are, as shown in FIG. Each outer edge (indicated by a broken line in the figure) is just before the collision. At this time point T4, the first stratified gas mixture 71 has a flame propagating to the portion indicated by the alternate long and short dash lines Fi and Fe in the drawing, and the second stratified gas mixture 72 has the flame to the portion indicated by the dashed dotted line Fc in the drawing. Propagating.

  In the first stratified mixture 71, the portions 71i and 71e outside the alternate long and short dash lines Fi and Fe (hereinafter referred to as outer portions) are not yet propagated, and are unburned mixtures. The outer portions 71e and 71i are diffused with the expansion of the first stratified air-fuel mixture 71 and mixed with the surrounding air, so that the outer portions 71e and 71i are leaner than when ignited. Similarly, also in the second stratified mixture 72, a portion 72c outside the alternate long and short dash line Fc (hereinafter referred to as an outer portion) diffuses with the expansion of the second stratified mixture 72, and is leaner than at the time of ignition. It has become a thing.

  At this time T4, in the region between the electrode 51a of the first spark plug 51 and the electrode 52a of the second spark plug 52 in the combustion chamber 40, the first stratified mixture that expands toward the exhaust side of the combustion chamber 40. The outer portion 71e of the 71 (the flow direction is indicated by an arrow Ee) and the outer portion 72c (the flow direction is indicated by an arrow Ec) of the second stratified mixture 72 expanding to the intake side face each other.

  Then, immediately after time T4, the outer portion 71e of the first stratified mixture 71 expanding to the exhaust side and the outer portion 72c of the second stratified mixture 72 expanding to the intake side collide with each other. When the first stratified mixture 71 and the second stratified mixture 72 are pressed against each other, the outer portion 71e on the exhaust side of the first stratified mixture 71 and the outer portion 72c of the second stratified mixture 72 are further diffused. I can't do that. As a result, the outer side portion 71e on the exhaust side of the first stratified gas mixture 71 and the outer side portion 72c of the second stratified gas mixture 72 are excessively diluted, and an overlean gas mixture is prevented from being generated in these portions 71e and 72c. can do.

  Further, at time T4, a squish flow (indicated by arrow S in the drawing) is generated between the squish surface 36 of the rising piston 30 and the intake valve 25f from the intake side to the center of the combustion chamber 40. ing. In the region between the nozzle portion 55a of the fuel injection valve 55 and the intake valve 25 in the combustion chamber 40, the outer portion 71i of the first stratified mixture 71 that expands toward the intake side of the combustion chamber 40 (the flow direction is indicated by the arrow Ei) And the squish flow S face each other.

  Then, immediately after time T4, the first stratified mixture 71 expanding to the intake side and the squish flow S from the intake side toward the center are pressed against each other, so that the outer portion 71i on the intake side of the first stratified mixture 71 becomes , Can no longer diffuse. As a result, it is possible to prevent the outer portion 71i on the intake side of the first stratified mixture 71 from being excessively diluted and generating an over-lean mixture. Further, by generating the squish flow S in the intake side region of the combustion chamber 40, the outer portion 71i of the first stratified mixture 71 expanding to the intake side is prevented from escaping into the clevis volume 43 on the intake side. is doing.

  As described above, in this embodiment, the fuel injection valve 55 is provided on the intake side of the ceiling wall central portion 22a of the combustion chamber 40, and the first spark plug 51 is provided on the exhaust side of the ceiling wall central portion 22a. Further, a second spark plug 52 is provided on the ceiling wall peripheral portion 22c. The fuel injection valve 55 injects fuel in a direction toward the electrode 51 a of the first spark plug 51 and in a direction toward the cavity 44 of the piston 30. The cavity 44 of the piston 30 receives the fuel from the fuel injection valve 55 and guides it to the electrode 52 a of the second spark plug 52. That is, the internal combustion engine 10 guides the fuel injected from the fuel injection valve 55 in the central portion 22a of the ceiling wall to the vicinity of the first spark plug 51 in the central portion 22a of the ceiling wall with the spray guide and A wall guide is used in the vicinity of the second spark plug 52 at the wall peripheral edge 22c.

  Thereby, separate stratified air-fuel mixtures 71 and 72 can be formed in the vicinity of the first spark plug 51 and in the vicinity of the second spark plug 52, respectively. By igniting the stratified mixture 71 and 72 and colliding the expanding stratified mixture 71 and 72 with each other, unburned portions (outer portions) 71e and 72c outside the stratified mixture 71 and 72 are diffused. It is possible to suppress the occurrence of over lean air-fuel mixture in the outer portions 71e and 72c.

  Further, in the present embodiment, the cavity wall 33 of the piston 30 has the piston central side edge 33 a facing the nozzle part 55 a of the fuel injection valve 55, and the piston peripheral edge 33 c is the electrode of the second spark plug 52. It faces 52a. For this reason, when the piston 30 is positioned near the top dead center, the fuel (second fuel spray) from the combustion injection valve 55 is received by the central side edge portion 33 a, and the received fuel is run along the cavity wall 33. It can be made to flow along the peripheral edge 33c which is the other edge. Thereby, it becomes possible to guide the fuel from the fuel injection valve 55 in the central portion 22a of the ceiling wall to the vicinity of the second spark plug 52.

  In the present embodiment, the second spark plug 52 is provided on the exhaust side of the ceiling wall peripheral portion 22c. Since the exhaust side of the ceiling wall peripheral portion 22c is a portion having a higher temperature than the intake side, the fuel introduced to the vicinity of the second spark plug 52, that is, the second fuel spray can be vaporized well. . Further, by providing the second spark plug 52 on the exhaust side of the ceiling wall peripheral portion 22c, the flow path cross-sectional area of the intake port 24 can be ensured as much as possible on the intake side of the ceiling wall peripheral portion 22c.

  In this embodiment, the fuel injection device is composed of one fuel injection valve 55, and fuel is injected into the fuel injection valve 55 toward the spark discharge part (electrode) 51 a of the first spark plug 51. The first injection hole 63 and the second injection hole 64 for injecting the fuel toward the central side edge 33a of the cavity wall 33 of the piston 30 are provided, and the first injection hole 63 and the second injection hole 64 are provided. The fuel was injected at the same time. By simply forming nozzle holes with different nozzle hole diameters and nozzle hole lengths in the nozzle portion of one fuel injector, two stratified mixtures are formed in the combustion chamber without using a fuel injector with a special structure. A fuel injection device for an internal combustion engine can be realized.

  Further, in the present embodiment, means for generating a squish flow toward the first spark plug 51 (squish flow generation) on the opposite side of the ceiling wall peripheral portion 22c of the combustion chamber 40 from the side where the second spark plug 52 is provided. As a means, a squish surface 36 is formed on the surface 25f of the intake valve 25 on the combustion chamber 40 side and the portion of the top surface 32 of the piston 30 facing the surface 25f so as to be parallel to the surface 25f. . When the piston 30 rises, a squish flow S from here to the center of the combustion chamber 40 can be generated between the squish surface 36 and the intake valve surface 25f, and is ignited and expanded by the first spark plug 51. The first stratified gas mixture 71 can be sandwiched between the squish flow S and the second stratified gas mixture that is ignited by the second spark plug 52 and expands. Thereby, it can suppress effectively that the outer parts 71i and 71e of the 1st stratified mixture 71 diffuse, and an over lean mixture is produced.

  The internal combustion engine according to this embodiment will be described with reference to FIGS. FIG. 7 is a view showing the positional relationship among the fuel injection valve, the spark plug, and the intake / exhaust valve, and is a view of the cylinder head as viewed from the piston side. FIG. 8 is a view showing the positional relationship between the cavity formed in the piston, the fuel injection valve, and the spark plug, and is a view of the piston top surface from the cylinder head side. In addition, about the structure which is common in Example 1, the same code | symbol is attached | subjected and description is abbreviate | omitted.

  As shown in FIG. 7, in the present embodiment, the second spark plug 52B that ignites the second stratified mixture on the ceiling wall 22B of the cylinder head 20 is connected to the outer edge 24e of the intake port 24 in the ceiling wall peripheral portion 22c. It is disposed at a portion sandwiched between the outer edge 26e of the exhaust port 26 and the peripheral edge 22e of the ceiling wall 22B.

  Along with the arrangement of the second spark plug 52B on the ceiling wall 22B, as shown in FIG. 8, a cavity 44B is formed in the piston 30B from the approximate center of the piston 30B to one side along the plane L. ing. That is, the cavity wall 33B that defines the shape of the cavity 44B is formed such that the edge 33Ba (hereinafter referred to as the center side edge) of the piston 30B is opposed to the nozzle 55a of the fuel injection valve 55. . The other edge 33Bc (hereinafter referred to as a peripheral edge) on the peripheral edge of the piston 30B is formed to face the electrode 52Ba of the second spark plug 52B. In the cavity wall 33B, the center side edge 33Ba and the peripheral edge 33Bc (hereinafter referred to as peripheral edge) are opposed and smoothly continuous.

  The cavity 44B of the piston 30B can receive the fuel spray flowing from the upper U to the lower D in the substantially central portion 40a of the combustion chamber 40 at the central side edge portion 33Ba, and in addition, at the central side edge portion 33Ba. The received fuel can be guided along the cavity wall 33B to the peripheral edge 33Bc on the other side.

  Thus, by constituting the ceiling wall 22B and the piston 30B of the cylinder head 20, the second fuel spray injected from the fuel injection valve 55 during the compression stroke of the internal combustion engine, that is, when the piston 30B is raised, The portion 22c can be guided toward the electrode 52Ba of the second spark plug 52B at a portion sandwiched between the outer edge 24e of the intake port 24 and the outer edge 26e of the exhaust port 26. As a result, the internal combustion engine can form the second stratified mixture 72 near the electrode 52Ba of the second spark plug 52B, that is, at the peripheral edge portion 40c of the combustion chamber 40.

  As described above, in the present embodiment, the second spark plug 52B is provided at a portion of the ceiling wall peripheral portion 22c of the combustion chamber 40 sandwiched between the outer edge 24e of the intake port 24 and the outer edge 26e of the exhaust port 26. Therefore, compared to the case where the second spark plug 52 is provided at a portion between the outer edges 26e of the two exhaust ports 26, the thermal load received by the second spark plug 52B can be reduced, and the exhaust port 26 Two stratified air-fuel mixtures can be formed in the combustion chamber 40 by ensuring the cross-sectional area of the flow path as much as possible. By igniting and colliding these two stratified mixtures, it is possible to suppress the generation of an over-lean mixture generated in the outer portion of the expanding stratified mixture.

  In each of the above-described embodiments, the second spark plug (52; 52B) includes the outer edge 24e of the intake port 24 and the exhaust port 26 of the ceiling wall peripheral portion 22c or the exhaust wall portion of the ceiling wall peripheral portion 22c. However, the portion where the second spark plug is provided is not limited to this. It may be a part spaced apart from the first spark plug 51 of the ceiling wall central part 22a so that a separate air-fuel mixture can be formed. For example, a second spark plug may be provided on the intake side of the ceiling wall peripheral part 22c. good.

  In each of the above-described embodiments, the first spark plug 51 and the second spark plug (52; 52B) ignite at the same time. However, it is also possible to set a time difference between the ignition timings of these two spark plugs. good. The first stratified mixture, which is ignited by the first spark plug 51 and expands, and the second stratified mixture, which is ignited and expanded by the second spark plug (52; 52B), collide with each other, and the outer portions of these stratified mixtures are collided. The ignition timing may be such that the diffusion of (unburned portion) can be effectively suppressed. For example, after the second spark plug (52; 52B) is ignited, the first spark plug 51 is ignited after a predetermined time has elapsed. It is good to do.

  Further, in each of the above-described embodiments, as the fuel injection device, two fuel sprays 61 and 62 having different flow paths are formed by injecting fuel in two directions with one fuel injection valve 55. However, the method of forming fuel sprays with different flow paths is not limited to this. It is only necessary to form separate fuel sprays toward the electrode 51a of the first spark plug 51 and the cavity (44; 44B) of the piston 30. It is good also as a structure which provides a some fuel injection valve and forms fuel spray for every fuel injection valve. For example, a fuel injection valve that injects fuel toward the first spark plug 51 and a fuel injection valve that injects fuel toward the cavity (44; 44B) of the piston 30 are separately provided in the central portion 22a of the ceiling wall. It is also preferable to provide it. If the fuel injection device is configured in this way, it becomes easy to inject fuel from each injection hole at different times, and the fuel injection toward the cavity (44; 44B) is injected into the first spark plug 51. Compared to, it can be done earlier. Thereby, it is possible to more easily realize the stratified mixture simultaneously in the vicinity of the first spark plug 51 and in the vicinity of the second spark plug (52; 52B).

  Further, in each of the embodiments described above, fuel penetration force (spray) is applied from the fuel injection valve 55 on the intake side of the center portion 22a of the ceiling wall of the combustion chamber 40 to the electrode 51a of the first spark plug 51 on the exhaust side. The guide is used to guide the fuel, but the method of guiding the fuel spray is not limited to this. Combustion is generated by forming a squish area on the top surface 32 of the piston 30 and the ceiling wall 22 of the combustion chamber 40 to generate a squish flow from the fuel injection valve 55 toward the first spark plug 51 by raising the piston 30. The fuel spray from the nozzle portion 55 a of the injection valve 55 may be guided to the electrode 51 a of the first spark plug 51. In addition, a spray guide and an air guide may be combined to guide fuel spray from the nozzle portion 55a of the fuel injection valve 55 to the periphery of the electrode 51a of the first spark plug 51.

  As described above, the internal combustion engine according to the present invention is useful for an in-cylinder spark ignition engine capable of stratified combustion in a combustion chamber, and is particularly suitable for a gasoline engine mounted as a prime mover in an automobile.

It is sectional drawing which shows the structure of the cylinder periphery of an internal combustion engine. It is a figure which shows the arrangement | positioning relationship of the fuel injection valve which concerns on Example 1, an ignition plug, and an intake / exhaust valve, and is the figure which looked at the cylinder head from the piston side. It is a figure which shows the arrangement | positioning relationship of the cavity formed in the piston which concerns on Example 1, a fuel injection valve, and a spark plug, and is the figure which looked at the piston top surface from the cylinder head side. It is a figure explaining the relationship between L / D ratio of the nozzle hole of the fuel injection valve which concerns on Example 1, and fuel spray. 3 is a timing chart showing fuel injection timing and ignition timing during stratified combustion of the internal combustion engine according to the first embodiment. FIG. 3 is a cross-sectional view illustrating a configuration around a cylinder of the internal combustion engine according to the first embodiment, and is a diagram illustrating an injection angle at the start of fuel injection (time point T1). It is sectional drawing which shows the structure of the cylinder periphery of the internal combustion engine which concerns on Example 1, and is a figure which shows the state (time T2) in which fuel injection was completed and fuel spray was formed. FIG. 3 is a cross-sectional view showing a configuration around a cylinder of the internal combustion engine according to the first embodiment, showing a state (time point T3) in which a fuel spray flows and a stratified mixture is formed in the vicinity of the first and second spark plugs, respectively. FIG. FIG. 3 is a cross-sectional view illustrating a configuration around a cylinder of the internal combustion engine according to the first embodiment, and illustrates a state (time T4) immediately before the stratified mixture ignited by the spark plug expands and collides with the stratified mixture. is there. It is a figure which shows the arrangement | positioning relationship of the fuel injection valve which concerns on Example 2, an ignition plug, and an intake / exhaust valve, and is the figure which looked at the cylinder head from the piston side. It is a figure which shows the arrangement | positioning relationship of the cavity formed in the piston which concerns on Example 2, a fuel injection valve, and a spark plug, and is the figure which looked at the piston top surface from the cylinder head side.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Internal combustion engine 12 Cylinder block 15 Cylinder wall 20 Cylinder head 22, 22B Ceiling wall 22a Ceiling wall center part 22c Ceiling wall peripheral part 24 Intake port 24e Outer edge of intake port 25 Intake valve 25f Intake valve surface 26 Exhaust port 26e Outer edge of exhaust port 27 Exhaust valve 30, 30B Piston 32 Top surface 33, 33B Cavity wall 33a, 33Ba Central side edge 33c, 33Bc Peripheral side edge 36 Squish surface 40 Combustion chamber 44, 44B Cavity 51 First spark plug 52 Second spark plug 51a , 52a, 52Ba Electrode (spark discharge part)
55 Fuel Injection Valve 55a Nozzle Unit 61 First Fuel Spray 62 Second Fuel Spray 63 First Injection Hole 64 Second Injection Hole 71 First Stratified Mixture 72 Second Stratified Mixture C Cylinder Bore Core L Planar EX Exhaust Side IN Intake Side S Squish flow

Claims (9)

An internal combustion engine capable of stratified combustion in a combustion chamber,
A first spark plug provided in the center of the ceiling wall of the combustion chamber;
A second spark plug provided at the periphery of the ceiling wall of the combustion chamber;
A fuel injection device provided at the center of the ceiling wall of the combustion chamber and capable of directly injecting fuel in two directions in the combustion chamber;
A piston provided with a cavity capable of receiving fuel from the fuel injection device and guiding the fuel to a spark discharge portion of the second spark plug;
With
An internal combustion engine, wherein the fuel injection device injects fuel in a direction toward the spark discharge portion of the first spark plug and in a direction toward the cavity. The internal combustion engine according to claim 1,
The cavity wall that defines the shape of the cavity is characterized in that one edge portion faces the nozzle portion of the fuel injection device and the other edge portion faces the spark discharge portion of the second spark plug. Internal combustion engine. An internal combustion engine according to claim 2,
The internal combustion engine, wherein the second spark plug is provided at a portion on the exhaust side of the peripheral portion of the ceiling wall of the combustion chamber. An internal combustion engine according to claim 2,
The internal combustion engine, wherein the second spark plug is provided in a portion sandwiched between an outer edge of the intake port and an outer edge of the exhaust port in the peripheral edge of the ceiling wall of the combustion chamber. The internal combustion engine according to any one of claims 2 to 4,
The fuel injection device is composed of one fuel injection valve,
The fuel injection valve is provided with a first injection hole for injecting fuel toward the spark discharge portion of the first spark plug and a second injection hole for injecting fuel toward one edge of the cavity wall of the piston. And
An internal combustion engine in which fuel is simultaneously injected from the first nozzle hole and the second nozzle hole. An internal combustion engine according to claim 5,
An internal combustion engine characterized in that the second nozzle hole has a nozzle hole shape set so that the tip speed of the injected fuel spray is larger than that of the first nozzle hole. The internal combustion engine according to claim 6,
The internal combustion engine, wherein the second nozzle hole has an L / D ratio that is a ratio between the nozzle hole length and the nozzle hole diameter set larger than that of the first nozzle hole. The internal combustion engine according to any one of claims 1 to 7,
An internal combustion engine characterized in that squish flow generating means for generating a squish flow toward the first spark plug is provided on the opposite side of the peripheral edge of the ceiling wall of the combustion chamber to the side where the second spark plug is provided. . An internal combustion engine according to claim 8,
The squish flow generating means is a combustion chamber side surface of an intake valve or an exhaust valve, and a piston top surface formed so that a portion facing the surface is parallel to the surface.

Images