JP2005090244A - Cylinder injection type spark ignition internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To set a compression ratio of an internal combustion engine as high as possible, and to enable stratified charge combustion also with respect to wider fluctuation of a fuel injection flow rate from a fuel injection valve, in a cylinder injection type spark ignition internal combustion engine. <P>SOLUTION: The cylinder injection type spark ignition internal combustion engine 10 is equipped with the fuel injection valve 1 provided in an intake valve 6 side of a cylinder head 11 and injecting fuel in a central direction of a combustion chamber 9, a first ignition plug 2 provided in an approximate center of the combustion chamber 9, and a second ignition plug 3 provided in a portion of the cylinder head 11 opposing to the fuel injection valve 1. A hump part 8a corresponding to a shape of an inner wall face of the cylinder head 11 is provided for a top part of a piston 8, and a first cavity 8b and a second cavity 8c are provided on the hump part 8a opposing to the first ignition plug 2 and the hump part 8a opposing to the second ignition plug 3, respectively. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a spark ignition internal combustion engine including a fuel injection valve that directly injects fuel into a combustion chamber.

  Conventionally, in a cylinder injection spark ignition internal combustion engine, stratified combustion is performed by locally forming an air-fuel mixture in the vicinity of a spark plug for the purpose of improving fuel consumption. For example, by providing a cavity at the center top of a piston, a technique for locally forming an air-fuel mixture in the vicinity of a spark plug by concentrating injected fuel in the cavity is disclosed (for example, Patent Document 1). reference.).

In addition, when a cavity is provided at the center top of the piston, depending on the fuel injection flow rate from the fuel injection valve, it may be difficult to reliably collect the fuel in the cavity, which makes it difficult to realize stratified combustion. Therefore, a technique has been disclosed in which a plurality of spark plugs are provided instead of providing the cavity, and the spark plug that ignites the air-fuel mixture is switched according to the fuel injection flow rate from the fuel injection valve (for example, (See Patent Document 2).
Japanese Patent Laid-Open No. 2-16984 JP-A-10-169446 JP 2000-179441 A JP-A-4-365828

  When stratified combustion is performed in an in-cylinder spark-ignition internal combustion engine, it is necessary to locally collect the fuel injected from the fuel injection valve around the spark plug, and if the fuel diffuses into the combustion chamber, stratified combustion There is a possibility that the fuel efficiency cannot be sufficiently improved by performing the above.

  Further, the degree of formation of the stratified mixture in the combustion chamber varies depending on the injection flow rate of the fuel injected from the fuel injection valve. That is, the time from the fuel injection to the formation of the air-fuel ratio suitable for stratified combustion differs between when the injection flow rate is low and when the injection flow rate is high. Specifically, as the fuel injection flow rate increases, the time from fuel injection to formation of an air-fuel ratio mixture suitable for stratified combustion becomes longer, and generally, the injected fuel is injected into the fuel chamber within the combustion chamber. Move further away from the valve. Therefore, in a cylinder injection spark ignition internal combustion engine having only one fuel spark plug, there is a possibility that efficient stratified combustion becomes difficult.

  Furthermore, in order to improve the fuel consumption of the internal combustion engine by stratified combustion, it is preferable to set the compression ratio of the internal combustion engine as high as possible.

  In the present invention, in view of the above-described problems, the compression ratio of the internal combustion engine is set as high as possible in the direct injection spark ignition internal combustion engine, and also for a wider variation in the fuel injection flow rate from the fuel injection valve. An object of the present invention is to provide an in-cylinder injection spark ignition internal combustion engine capable of stratified combustion.

  In order to solve the above-described problems, the present invention focuses on the shape of the piston top portion facing the fuel injection valve and the spark plug in the cylinder injection type spark ignition internal combustion engine. This is because the compression ratio of the internal combustion engine can be increased by the shape of the piston top, and the fuel injected from the fuel injection valve can be concentrated in the vicinity of the spark plug.

  Accordingly, the present invention first provides a fuel injection valve that is provided on the intake valve side of the cylinder head and injects fuel toward the center of the combustion chamber, and is provided substantially in the center of the combustion chamber. In-cylinder injection spark ignition internal combustion engine comprising: a first ignition plug that ignites; and a second ignition plug that is provided in a portion of the cylinder head facing the fuel injection valve and ignites an air-fuel mixture in the combustion chamber. In the engine, a hill corresponding to the shape of the inner wall surface of the cylinder head is provided at the top of the piston, and the first cavity and the second spark plug are provided in the hill facing the first spark plug. A second cavity is provided in the opposing hill-shaped part.

  In the cylinder injection spark ignition internal combustion engine configured as described above, the volume of the combustion chamber when the position of the piston becomes top dead center is reduced by providing a hill-shaped portion at the top of the piston, Thus, the compression ratio of the internal combustion engine can be increased.

  In addition, by providing a first spark plug substantially at the center of the combustion chamber and a second spark plug in the portion of the cylinder head facing the fuel injection valve, the fuel injection valve, the first spark plug, The two spark plugs are positioned approximately in a straight line. Even when the fuel injection flow rate from the fuel injection valve increases and an air-fuel ratio stratified mixture suitable for stratified combustion is formed at a position away from the fuel injection valve, the first spark plug and the second spark plug Thus, it becomes possible to ignite the stratified mixture more reliably. Furthermore, by providing a cavity in the hill-shaped part facing each of the first spark plug and the second underline, the stratified mixture to be ignited by each of the first spark plug and the second spark plug is more reliably ensured. It is possible to concentrate in the vicinity of each spark plug.

  As a result, the compression ratio of the internal combustion engine is set as high as possible in the cylinder injection spark ignition internal combustion engine, and the fuel injection flow rate from the fuel injection valve is stratified in a wider range from the low injection flow rate to the high injection flow rate. Combustion is possible.

  Further, in addition to the in-cylinder injection spark ignition internal combustion engine, the following in-cylinder injection spark ignition internal combustion engine is also useful. That is, a fuel injection valve that is provided on the intake valve side of the cylinder head and injects fuel toward the center of the combustion chamber, and a first ignition that is provided substantially in the center of the combustion chamber and ignites the air-fuel mixture in the combustion chamber In a direct injection spark ignition internal combustion engine, comprising: a stopper; and a second ignition stopper provided at a portion of the cylinder head facing the fuel injection valve and igniting an air-fuel mixture in the combustion chamber. Provided with a hill-shaped portion corresponding to the shape of the inner wall surface of the cylinder head, and communicated from the hill-shaped portion facing the fuel injection valve to the hill-shaped portion facing the second spark plug. And an air-fuel mixture forming groove opened on the first spark plug side.

  A difference from the above-described in-cylinder spark-ignition internal combustion engine is that an air-fuel mixture forming groove is provided in the hill-shaped portion instead of a cavity. By providing the air-fuel mixture forming groove, the air-fuel mixture injected from the fuel injection valve is present in a limited region surrounded by the air-fuel mixture forming groove and the inner wall surface of the cylinder head. The air-fuel mixture is prevented from diffusing into the combustion chamber. Further, since the air-fuel mixture is guided to the position where the first spark plug and the second spark plug are provided by the air-fuel mixture formation groove, more efficient stratified combustion is possible.

In addition, the cross-sectional area of the air-fuel mixture forming groove increases as it proceeds from the fuel injection valve side to the second spark plug side, that is, the air-fuel mixture forming groove extends from the fuel injection valve side to the second spark plug side. By becoming the shape which spreads toward the end, the injected fuel becomes easy to flow in the direction of the first spark plug and the second spark plug. As a result, even when the fuel injection flow rate from the fuel injection valve increases, it becomes possible to form an air-fuel ratio suitable for stratified combustion in the vicinity of the second spark plug, that is, an air-fuel ratio that is not excessive in stratified combustion. .

  As a result, the compression ratio of the internal combustion engine is set as high as possible in the cylinder injection spark ignition internal combustion engine, and the fuel injection flow rate from the fuel injection valve is stratified in a wider range from the low injection flow rate to the high injection flow rate. Combustion is possible.

  Here, in the above-described in-cylinder injection spark ignition internal combustion engine, the installation position of the fuel injection valve is a portion of the cylinder head below the intake valve, and the installation position of the second spark plug is the cylinder head, The part below the exhaust valve.

  Thus, by installing the fuel injection valve and the second spark plug, the combustion gas generated in the combustion chamber, particularly the combustion gas generated by ignition by the second spark plug, is quickly discharged outside the combustion chamber. It becomes possible to do. In addition, the fuel injected by the fuel injection valve and the fresh air sucked into the combustion chamber by opening the intake valve are mixed more quickly, and an air-fuel ratio mixture suitable for stratified combustion is more reliably formed. The

  Furthermore, an opening between the combustion chamber and the exhaust port is provided in the horizontal direction, and an inner wall surface of the cylinder head provided with the second spark plug is provided in a direction perpendicular to the opening. As a result, the air-fuel mixture is more reliably ignited by the second spark plug, and the combustion gas generated by the combustion of the fuel can be quickly discharged outside the combustion chamber.

  The second spark plug may be constituted by a plurality of spark plugs. Thereby, ignition to the air-fuel mixture by the second spark plug is more reliably performed.

  Here, depending on the fuel injection flow rate from the fuel injection valve, the time from the fuel injection until the air-fuel ratio mixture suitable for stratified combustion is formed varies, and the position where the mixture is formed in the combustion chamber also varies. This is done as described above. Therefore, when the fuel injection flow rate from the fuel injection valve is less than or equal to a predetermined reference injection flow rate, the air-fuel mixture formed in the combustion chamber is ignited by the first spark plug, and fuel injection from the fuel injection valve is performed. When the flow rate exceeds the predetermined reference injection flow rate, the air-fuel mixture formed in the combustion chamber is also ignited by the second spark plug.

  When the fuel injection flow rate from the fuel injection valve is relatively small, the time from the fuel injection until the air-fuel ratio mixture suitable for stratified combustion is formed is relatively short, and the air-fuel mixture is formed in the combustion chamber. The position is near the center of the combustion chamber. On the other hand, when the fuel injection flow rate from the fuel injection valve is relatively large, the time from the fuel injection to the formation of the air-fuel ratio suitable for stratified combustion is relatively long. It is formed near the inner wall of the cylinder head facing the valve, that is, near the second spark plug.

  Therefore, by using different spark plugs that ignite the air-fuel mixture according to the fuel injection flow rate from the fuel injection valve, more efficient stratified combustion becomes possible. Therefore, the predetermined reference injection flow rate is a threshold value of the fuel injection flow rate from the fuel injection valve for properly using the spark plug that ignites the air-fuel mixture in order to perform more efficient stratified combustion.

Further, when the fuel injection flow rate from the fuel injection valve exceeds the predetermined reference injection flow rate, it is useful to perform the fuel injection from the fuel injection valve in two steps. When the fuel injection flow rate is relatively large, an air-fuel mixture having a certain concentration exists also between the first spark plug and the second spark plug. In such a case, even if ignition is performed with the first spark plug and the second spark plug, the air-fuel mixture between the first spark plug and the second spark plug may not be burned sufficiently, so stratified combustion Is difficult to perform efficiently. Therefore, by dividing the fuel injection into two times, the fuel injected earlier can be concentrated in the vicinity of the second spark plug, and the fuel injected later can be concentrated in the vicinity of the first spark plug. As a result, the injected fuel can be more reliably burned by stratified combustion.

  In the in-cylinder spark ignition internal combustion engine, the compression ratio of the internal combustion engine is set as high as possible, and stratified combustion is possible even with a wider variation in the fuel injection flow rate from the fuel injection valve.

  Here, an embodiment of a direct injection spark ignition internal combustion engine according to the present invention will be described based on the drawings.

  FIG. 1 is a longitudinal sectional view of one cylinder of a four-cycle gasoline engine (hereinafter simply referred to as “internal combustion engine”) 10 as an in-cylinder injection spark ignition internal combustion engine. FIG. 2 is a top view of the combustion chamber 9 of the internal combustion engine 10 shown in FIG. 1 as viewed from the cylinder head 11 side.

  The internal combustion engine 10 includes a piston 8 that reciprocally slides in the axial direction in a cylinder including a cylinder head 11 and a cylinder block 12. An intake port 4 and an exhaust port 5 are provided on the cylinder head 11 side, and the communication between the combustion chamber 9 and the intake port 4 and the exhaust port 5 is performed by opening the intake valve 6 and the exhaust valve 7. Done. Also, the opening between the intake port 4 and the combustion chamber 9 is indicated by a dotted line in FIG. 2 as the opening 4a, and the opening between the exhaust port 5 and the combustion chamber 9 is indicated as an opening 5a.

  The fuel injection valve 1 is provided in the cylinder head 11 below the intake valve 6, and the fuel injection valve 1 is a valve that injects fuel toward the center of the combustion chamber 9. A first spark plug 2 is provided at a position sandwiched between the intake-side opening 4 a and the exhaust-side opening 5 a, and substantially in the center of the combustion chamber 9. Further, a second spark plug 3 is provided in the cylinder head 11 facing the fuel injection valve 1 across the center of the combustion chamber 9. Here, as shown in FIG. 1 and FIG. 2, the fuel injection valve 1, the first spark plug 2, and the second spark plug 3 are positioned substantially in a straight line. The exhaust-side opening 5a is provided in a horizontal direction perpendicular to the axial direction of the cylinder, and the inner wall of the cylinder head 11 provided with the second spark plug 3 is in the axial direction of the cylinder. It is provided in the vertical direction that is parallel.

  Here, as shown in FIG. 1, the top portion of the piston 8 is provided with a hill-shaped portion 8 a having a shape along the inner wall surface of the cylinder head 11 forming the combustion chamber 9. FIG. 1 is a view when the piston 8 is located near the top dead center. Therefore, when the piston 8 is located near the top dead center, the hill-shaped portion 8a reduces the distance between the inner wall surface of the cylinder head 11 and the top surface of the piston, thereby reducing the volume of the combustion chamber 9. As a result, the compression ratio of the internal combustion engine 10 increases.

  Further, in the hill-shaped portion 8, a first cavity 8 b that opens to the first spark plug 2 side is provided at a portion facing the first spark plug 2, and a second ignition is performed at a portion facing the second spark plug 3. A first cavity 8c that opens to the stopper 3 side is provided. The first cavity 8b and the second cavity 8c are independent cavities in the hill-shaped portion 8a.

In the internal combustion engine 10 configured as described above, the compression ratio of the internal combustion engine 10 can be increased by the hill-shaped portion 8 a of the piston 8, and the air-fuel mixture formed by the fuel injected from the fuel injection valve 1. By concentrating the gas in the first cavity 8b or the second cavity 8c, it becomes possible to form a stratified mixture near the first spark plug 2 or the second spark plug 3. And it becomes possible to aim at the improvement of the fuel consumption of the internal combustion engine 10 by performing stratified combustion. In addition, since the inner wall of the cylinder head 11 provided with the second spark plug 3 is in the vertical direction, the air-fuel mixture flowing from the direction of the fuel injection valve 1 can be more reliably ignited. In addition, since the exhaust-side opening 5a is provided in a horizontal direction perpendicular to the axial direction of the cylinder, the combustion gas generated in the combustion chamber 9, particularly the ignition of the second spark plug 3 It becomes possible to discharge the combustion gas generated by the above to the combustion chamber 9 more easily.

  The flow rate of the fuel injected from the fuel injection valve 1 varies depending on the operation region such as the engine speed of the internal combustion engine 10 and the engine load, and accordingly, the time required for fuel injection also varies. Therefore, the state of the air-fuel mixture formed in the combustion chamber 9 varies depending on the operating region of the internal combustion engine 10, and the conditions for efficient stratified combustion vary. Therefore, stratified combustion control for performing more efficient stratified combustion in accordance with the operating region of the internal combustion engine 10 will be described with reference to FIGS. 3 and 4. The stratified combustion control is executed by an ECU (not shown) which is an electronic control unit.

  FIG. 3 is a control flowchart for executing the stratified combustion control. FIG. 4 is a diagram in which the operating region of the internal combustion engine 10 is classified into four regions (R1, R2, R3, R4) corresponding to stratified combustion. The horizontal axis indicates the engine speed of the internal combustion engine 10 and is calculated from a detection signal from a crank position sensor or the like (not shown). The vertical axis indicates the engine load of the compression ignition internal combustion engine 10 and is calculated from a detection signal from an accelerator opening sensor (not shown). Here, as shown in FIG. 4, the four regions R1, R2, R3, and R4 indicate the engine speed (V1, V2, V3, V4) and the engine load (T1, T2, T3, T4) of the internal combustion engine 10, respectively. Determined by. Here, the relationship between the engine rotation speeds (V1, V2, V3, V4) is V1 <V2 <V3 <V4. The relationship between the engine loads (T1, T2, T3, T4) is T1 <T2 <T3 <T4. Based on the operation region of the internal combustion engine 10 shown in FIG. 4, the stratified combustion control shown in FIG. 3 will be described below.

  First, in S101, it is determined whether or not stratified combustion is possible in the internal combustion engine 10. Specifically, from the signals of the crank position sensor and the accelerator opening sensor, the operating region of the internal combustion engine 10 is one of the regions other than R4 that is an operating region where stratified combustion is impossible, that is, any of the regions R1, R2, and R3. It is determined whether or not it belongs to the area. When the operating region of the internal combustion engine 10 belongs to the region R4, it is difficult to perform stratified combustion because the engine load and engine speed of the internal combustion engine 10 are excessive. If it is determined that the stratified charge combustion is possible in the internal combustion engine 10, the process proceeds to S102, and if it is determined that the stratified charge combustion is not possible in the internal combustion engine 10, the process proceeds to S108.

  In S102, the injection flow rate Q of the fuel injected from the fuel injection valve 1 is calculated from the engine load of the internal combustion engine 10 and the engine speed. As the engine load increases or the engine speed increases, the fuel injection flow rate Q also increases. When the process of S102 ends, the process proceeds to S103.

  In S103, it is determined whether or not the fuel injection flow rate Q calculated in S102 is a small injection flow rate. In other words, it is determined whether or not the operating range of the internal combustion engine 10 belongs to R1. If it is determined that the fuel injection flow rate Q is a small injection flow rate, the process proceeds to S104, and if it is determined that the fuel injection flow rate Q is not a small injection flow rate, the process proceeds to S105.

In S104, the fuel is injected from the fuel injection valve 1, and the stratified mixture formed by the fuel is ignited. At this time, since the fuel has a small injection flow rate, the fuel injection timing is when the piston 8 is relatively close to the top dead center of the compression stroke. Therefore, the fuel injected from the fuel injection valve 1 is mixed with fresh air flowing into the combustion chamber 9 from the intake port 4. However, since the fuel injection flow rate is small, the air-fuel mixture can only reach a position near the center of the combustion chamber 9. Not reach. Accordingly, the air-fuel mixture is concentrated in the first cavity 8b, and when the piston 8 reaches the vicinity of the top dead center, a stratified air-fuel mixture is formed around the first spark plug 2. In this case, stratified combustion is more reliably performed by igniting the stratified mixture by the first spark plug 2. When the process of S104 ends, this control ends.

  In S105, it is determined whether or not the fuel injection flow rate Q calculated in S102 is a medium injection flow rate. In other words, it is determined whether or not the operating range of the internal combustion engine 10 belongs to R2. If it is determined that the fuel injection flow rate Q is a medium injection flow rate, the process proceeds to S106, and if it is determined that the fuel injection flow rate Q is not a medium injection flow rate, the fuel injection flow rate Q is a large injection flow rate, that is, an internal combustion engine. This means that the ten operation areas belong to the area R3, and the process proceeds to S107.

  In S106, fuel is injected from the fuel injection valve 1 and ignition is performed on the stratified mixture formed by the fuel. At this time, since the injection flow rate of the fuel is medium, the fuel injection timing is a point in time when the piston 8 is relatively far from the top dead center of the compression stroke in the compression stroke. Therefore, the fuel injected from the fuel injection valve 1 is mixed with fresh air flowing into the combustion chamber 9 from the intake port 4. However, since the fuel injection flow rate is medium, the air-fuel mixture faces the fuel injection valve 1. It reaches the vicinity of the second spark plug 3 at the position. Therefore, when the piston 8 reaches the vicinity of the top dead center, the air-fuel mixture is concentrated in the first cavity 8b and the second cavity 8c, and stratified and mixed around the first spark plug 2 and the second spark plug 3 Qi is formed. In this case, the stratified combustion is more reliably performed by igniting the stratified mixture by the first spark plug 2 and the second spark plug 3. When the process of S106 ends, this control ends.

  In S107, as described above, since the fuel injection flow rate Q calculated in S102 is a large injection flow rate, the fuel injection timing is further increased from the top dead center of the compression stroke of the piston 8 as compared with the above-described middle case. It's time to leave. Here, since the fuel injection flow rate Q is large, the number of fuel injections is divided into two. Thus, when the piston 8 reaches the top dead center of the compression stroke, the fuel injected first reaches the vicinity of the second spark plug 3 mainly because the injection distance in the combustion chamber 9 becomes long. Further, the last injected fuel has a short injection distance in the combustion chamber, and therefore mainly reaches only near the center of the combustion chamber 9.

  Therefore, when the piston 8 reaches the vicinity of the top dead center, the air-fuel mixture is efficiently concentrated in the first cavity 8b and the second cavity 8c, and further in the space between the first cavity 8b and the second cavity 8c. The remaining air-fuel mixture, in other words, the amount of air-fuel mixture not formed as a stratified air-fuel mixture around the spark plug can be reduced as much as possible. And, by igniting the stratified mixture by the first spark plug 2 and the second spark plug 3, stratified combustion is more reliably performed. When the process of S107 ends, this control ends.

  In S108, since the operation region of the internal combustion engine 10 belongs to R4 and stratified combustion is not possible, homogeneous combustion is performed. In the homogeneous combustion, fuel is injected into the combustion chamber 9 in the intake stroke to form a more homogeneous mixture in the combustion chamber 9 and ignited by the first spark plug 2 and the second spark plug 3. When the process of S108 ends, this control ends.

  According to the present control, the compression ratio of the internal combustion engine 10 is set as high as possible by providing the hill portion 8a in the piston 8, and the fuel from the fuel injection valve 1 is set by the first cavity 8b and the second cavity 8c. Even when the injection flow rate varies from a small injection flow rate to a large injection flow rate, the stratified mixture can be concentrated around the first spark plug 2 or the second spark plug 3 and stratified combustion can be executed more reliably. Become. That is, stratified combustion is possible even with a wide variation in the fuel injection flow rate from the fuel injection valve 1.

  FIG. 5 and FIG. 5 show another embodiment of the direct injection spark ignition internal combustion engine that increases the compression ratio of the internal combustion engine and enables stratified combustion even when the fuel injection flow rate from the fuel injection valve varies widely. 6 will be described. FIG. 5 is a longitudinal sectional view of one cylinder of the internal combustion engine 10. FIG. 6 is a top view of the combustion chamber 9 of the internal combustion engine 10 shown in FIG. 5 as viewed from the cylinder head 11 side. In addition, about the component same as the internal combustion engine 10 shown in FIG. 1 and FIG. 2, the description is abbreviate | omitted by attaching | subjecting the same reference number.

  The internal combustion engine 10 according to the present embodiment differs from the internal combustion engine 10 shown in FIGS. 1 and 2 in the number of second spark plugs 3 and the shape of a hill-shaped portion 8 a provided on the top of the piston 8. . In the internal combustion engine 10 in the present embodiment, the second spark plug 3 is composed of two spark plugs, second spark plugs 3a and 3b. Further, an air-fuel mixture forming groove 8d is provided instead of the first cavity 8b and the second cavity 8c. The air-fuel mixture forming groove 8d is a groove extending from a portion of the hill-shaped portion 8a facing the fuel injection valve 1 to a portion of the hill-shaped portion 8a facing the second spark plugs 3a and 3b. Opened to the stopper 2 side. Further, the cross-sectional area of the air-fuel mixture forming groove 8d gradually becomes wider from the fuel injection valve 1 toward the second spark plugs 3a and 3b. Therefore, as shown in FIG. 6, the fuel injector 1 has a divergent shape from the fuel injection valve 1 toward the second spark plugs 3a and 3b. By forming the mixture formation groove 8d in such a shape, when performing stratified combustion, the mixture formed by the fuel injected from the fuel injection valve 1 and the fresh air flows in the mixture formation groove 8d. Can be made smoother.

  In the internal combustion engine 10 configured as described above, the fuel injected from the fuel injection valve 1 for performing stratified combustion is mixed with fresh air flowing into the combustion chamber 9 from the intake port 4, and then the mixture formation groove It reaches the position of the first spark plug 2 or the second spark plugs 3a, 3b along the shape of 8d. Therefore, the air-fuel mixture for stratified combustion is concentrated around the first spark plug 2 or the second spark plugs 3a and 3b without widely diffusing into the combustion chamber 9, enabling more efficient stratified combustion. It becomes.

  Here, also in the internal combustion engine 10 according to the present embodiment, the stratified combustion control shown in FIG. 4 can be executed. That is, when the operating region of the internal combustion engine 10 belongs to an operating region in which stratified combustion is possible and the fuel injection flow rate from the fuel injection valve 1 is small, the first spark plug 2 When the stratified mixture is ignited and the fuel injection flow rate from the fuel injection valve 1 is medium, the stratified mixture is ignited by the first spark plug 2 and the second spark plugs 3a and 3b. Further, when the fuel injection flow rate from the fuel injection valve 1 is large, the number of times of fuel injection from the fuel injection valve 1 is divided into two, and the first ignition plug 2 and the second ignition plugs 3a, 3b. To ignite the stratified mixture.

  In this way, the compression ratio of the internal combustion engine 10 is set as high as possible, and the first ignition is performed even when the fuel injection flow rate from the fuel injection valve 1 varies from the small injection flow rate to the large injection flow rate. It is possible to concentrate the stratified mixture around the plug 2 or the second spark plugs 3a and 3b, and to perform stratified combustion more reliably. That is, stratified combustion is possible even with a wide variation in the fuel injection flow rate from the fuel injection valve 1.

  As shown in the present embodiment, by providing two spark plugs of the second spark plugs 3a and 3b as the second spark plug 3, the air-fuel mixture flowing along the air-fuel mixture forming groove 8d having a divergent shape is formed. Thus, ignition can be performed more reliably. The number of second spark plugs is not limited to two, and may be one or more.

1 is a longitudinal sectional view of one cylinder in a direct injection spark ignition internal combustion engine according to an embodiment of the present invention. In the cylinder injection type spark ignition internal combustion engine which concerns on embodiment of this invention, it is a top view of the piston top part seen from the cylinder head side. 3 is a control flowchart for executing stratified combustion control in the direct injection spark ignition internal combustion engine according to the embodiment of the present invention. In the direct injection spark ignition internal combustion engine according to the embodiment of the present invention, the operation region of the internal combustion engine is classified into four regions corresponding to stratified combustion. FIG. 3 is a second longitudinal sectional view of one cylinder in the direct injection spark ignition internal combustion engine according to the embodiment of the present invention. FIG. 6 is a second top view of the piston top as viewed from the cylinder head side in the direct injection spark ignition internal combustion engine according to the embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 .... Fuel injection valve 2 .... First spark plug 3 .... Second spark plug 3a ... Second spark plug 3b ... Second spark plug 4 .... Intake port 4a ... Opening 5 ... Exhaust port 5a ... Opening 6 ... Intake valve 7 ... Exhaust valve 8 ... Piston 8a ... Hill-shaped Part 8b ··· First cavity 8c ··· Second cavity 8d · · · Mixture formation groove 9 · · · Combustion chamber 10 · · · Internal combustion engine 11 · · · Cylinder head 12 ··· ··Cylinder block

Claims (8)

A fuel injection valve that is provided on the intake valve side of the cylinder head and injects fuel toward the center of the combustion chamber;
A first spark plug that is provided substantially in the center of the combustion chamber and ignites an air-fuel mixture in the combustion chamber;
In a cylinder injection spark ignition internal combustion engine comprising: a second spark plug provided in a portion of the cylinder head facing the fuel injection valve and igniting an air-fuel mixture in the combustion chamber;
A hill-shaped portion corresponding to the shape of the inner wall surface of the cylinder head is provided at the top of the piston, and the hill-shaped portion facing the first spark plug is opposed to the first cavity and the second spark plug. A cylinder injection type spark ignition internal combustion engine characterized in that a second cavity is provided in a hill-shaped portion. A fuel injection valve that is provided on the intake valve side of the cylinder head and injects fuel toward the center of the combustion chamber;
A first spark plug that is provided substantially in the center of the combustion chamber and ignites an air-fuel mixture in the combustion chamber;
In a cylinder injection spark ignition internal combustion engine comprising: a second spark plug provided in a portion of the cylinder head facing the fuel injection valve and igniting an air-fuel mixture in the combustion chamber;
A hill-shaped portion corresponding to the shape of the inner wall surface of the cylinder head is provided at the top of the piston, and the hill-shaped portion facing the second spark plug from the hill-shaped portion facing the fuel injection valve. An in-cylinder injection spark ignition internal combustion engine characterized in that an air-fuel mixture forming groove is provided which communicates with a portion and opens on the first spark plug side. 3. The direct injection spark ignition internal combustion engine according to claim 2, wherein a cross-sectional area of the air-fuel mixture forming groove increases as the fuel injection valve side advances toward the second spark plug side. The fuel injection valve is provided in a portion of the cylinder head below the intake valve,
The in-cylinder spark-ignition internal combustion engine according to any one of claims 1 to 3, wherein the second spark plug is provided in a portion of the cylinder head below the exhaust valve. Openings between the combustion chamber and the exhaust port are provided in a horizontal direction,
The in-cylinder injection spark ignition internal combustion engine according to claim 4, wherein an inner wall surface of the cylinder head provided with the second ignition plug is provided in a direction perpendicular to the opening. The in-cylinder injection spark ignition internal combustion engine according to any one of claims 1 to 3, wherein the second spark plug is constituted by a plurality of spark plugs. When the fuel injection flow rate from the fuel injection valve is equal to or less than a predetermined reference injection flow rate, the first spark plug ignites the air-fuel mixture formed in the combustion chamber,
2. The air-fuel mixture formed in the combustion chamber is also ignited by the second spark plug when the fuel injection flow rate from the fuel injection valve exceeds the predetermined reference injection flow rate. The in-cylinder injection spark ignition internal combustion engine according to claim 6. The cylinder according to claim 7, wherein when the fuel injection flow rate from the fuel injection valve exceeds the predetermined reference injection flow rate, fuel injection from the fuel injection valve is performed in two steps. Internal injection spark ignition internal combustion engine.

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