JP2006299851A - Internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an internal combustion engine capable of executing stable stratified spark ignition operation in a light load operation area. <P>SOLUTION: The internal combustion engine is formed so that a combustion chamber 25 is divided into two spaces consisting of a higher part combustion chamber 25a and lower part combustion chamber 25b which are independent from each other when a piston 22 is on a top dead center position side from a predetermined position, and equipped with a fuel injection valve37 and an ignition plug 35 arranged so as to face the lower part combustion chamber. In the internal combustion engine, fuel is injected by a fuel injection valve at the latter half of a compression stroke so as to form a stratified mixture in the lower part combustion chamber, whereby more fuel can be collected in an area near the ignition plug. As a result, the stable stratified spark ignition operation can be executed in a light load operation area so that fuel consumption can be improved. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an internal combustion engine that operates in a spark ignition system in which an air-fuel mixture including air and fuel is formed in a combustion chamber, and the air-fuel mixture is ignited by a spark generated by an ignition plug and burned.

Conventionally, the stratified mixture has been made so that the spatial distribution density (fuel density) of the fuel contained in the mixture supplied for combustion in the combustion chamber of the internal combustion engine is higher in the region near the spark plug than in other regions. There is known an internal combustion engine that performs an operation by a stratified spark ignition system (stratified spark ignition operation) that is formed and ignited by a spark generated by a spark plug and burned (spark ignition combustion). (See Patent Document 1).
JP 2000-104550 A

  In this conventional internal combustion engine, by performing a stratified spark ignition operation, the amount of fuel that is discharged unburned is changed to form a homogeneous mixture with a uniform fuel density and a uniform fuel density. Can be reduced as compared with the case of performing the operation by the homogeneous spark ignition system (homogeneous spark ignition operation) in which spark ignition is performed. Therefore, according to this internal combustion engine, more of the fuel contained in the air-fuel mixture can be burned, so that the fuel consumption rate (fuel consumption) can be improved.

  However, when the load of the internal combustion engine is an extremely light load (during extremely light load operation), the amount of fuel contained in the mixture supplied for combustion is small. For this reason, the fuel density in the vicinity of the spark plug decreases when the spark plug generates a spark. As a result, even if the spark plug generates sparks, the air-fuel mixture may not be properly ignited, and there has been a problem that stable stratified spark ignition operation cannot be performed in the extremely light load operation region.

  The present invention has been made to address the above-described problems, and one of its purposes is to provide an internal combustion engine capable of performing a stratified spark ignition operation stably in a light load operation region. is there. In order to achieve the above object, an internal combustion engine according to the present invention includes a cylinder block in which a cylinder bore is formed, a cylinder head disposed on the cylinder block, a piston that reciprocates within the cylinder bore, and at least a wall surface of the cylinder bore. A fuel injection means for injecting fuel into a combustion chamber constituted by the lower surface of the cylinder head and the top surface of the piston, a spark ignition means for generating a spark in the combustion chamber, and introducing air into the combustion chamber Then, an air-fuel mixture containing the introduced air and the fuel injected by the fuel injection means is formed in the same combustion chamber, and the air-fuel mixture thus formed is ignited and burned by the spark generated by the spark ignition means. Spark ignition operation execution means for performing operation by a spark ignition system.

  The combustion chamber is divided into two spaces consisting of a first space and a second space that are independent from each other when the piston is on the top dead center position side from a predetermined position, and the piston is at the top dead center position. The first space volume ratio, which is the ratio of the volume of the first space when the piston is at the predetermined position to the volume of the first space, is the second space when the piston is at the top dead center position. The second space volume ratio, which is the ratio of the volume of the second space when the piston is at the predetermined position, is larger than the second space volume ratio.

The fuel injection means is arranged to face the first space.
The spark ignition means is arranged to face the first space.
The spark ignition operation execution means is configured to cause the fuel density, which is a spatial distribution density of fuel contained in the air-fuel mixture in the first space, to be higher in the area near the spark ignition means than in other areas. A stratified spark ignition operation is performed in which the fuel is injected by the injection means to form a stratified mixture, and the stratified mixture is ignited by a spark generated by the spark ignition means and burned. Including means.

  According to this, when the piston is at the top dead center position side from the predetermined position, the combustion chamber is divided into two spaces composed of the first space and the second space that are independent from each other. Thereby, in the period when the combustion chamber is divided, the region in which the fuel in the first space can diffuse becomes narrower than in the case where the combustion chamber is not divided into two spaces. On the other hand, the fuel injection means and the spark ignition means are arranged so as to face the first space. Further, the stratified spark ignition operation execution means injects fuel by the fuel injection means so as to form a stratified mixture in the first space.

  As described above, more fuel can be collected in a region near the spark ignition means. As a result, for example, in the light load operation region where the amount of fuel contained in the air-fuel mixture supplied for combustion is small, the region where the operation by the stratified spark ignition method (stratified spark ignition operation) can be expanded, and the fuel efficiency is improved. Can be.

  Furthermore, the ratio of the volume of the first space when the piston is at the predetermined position to the volume of the first space when the piston is at the top dead center position (first space volume ratio) is It is larger than the ratio of the volume of the second space when the piston is in the predetermined position to the volume of the second space at the point position (second space volume ratio).

  Therefore, when the piston moves from the predetermined position to the top dead center position, the gas in the first space is compressed more than the gas in the second space. For this reason, the temperature of the gas in the first space is higher than the temperature of the gas in the second space. As a result, the air-fuel mixture can be reliably burned in the first space even in the extremely light load operation region.

  In this case, it is preferable that the stratified spark ignition operation execution means injects the fuel by the fuel injection means in the latter half of the compression stroke.

  According to this, during the stratified spark ignition operation, fuel is injected in the latter half of the compression stroke. This shortens the time from the time when the fuel is injected (fuel injection timing) to the time when the spark ignition means generates a spark (spark ignition timing). That is, the fuel contained in the formed stratified mixture is diffused, so that the stratified mixture can be ignited before the fuel density of the stratified mixture becomes spatially uniform. As a result, the stratified spark ignition operation can be performed more reliably even in an extremely light load operation region where the amount of fuel contained in the air-fuel mixture provided for combustion is small.

In this case, air is introduced into the combustion chamber, and an air-fuel mixture including the introduced air, fuel injected by the fuel injection means, and combustion gas is formed in the combustion chamber, and the air-fuel mixture formed is compressed. Self-ignition operation execution means for performing operation by a premixed compression self-ignition method in which self-ignition is performed in the first space and the second space to burn
When the load of the internal combustion engine is a high load equal to or higher than a predetermined high load threshold, the self-ignition operation execution means is operated to operate the internal combustion engine, and the load of the internal combustion engine is a light load smaller than the high load threshold. When there is, operation switching means for operating the internal combustion engine by the stratified spark ignition operation execution means of the spark ignition operation execution means,
Is preferably provided.

  According to this, in the high load operation region, by performing the operation by the premixed compression self-ignition method (self-ignition operation), it is possible to improve the fuel efficiency and reduce the amount of NOx generated by the combustion. Can be reduced. Furthermore, as described above, since the first space volume ratio is larger than the second space volume ratio, the temperature of the gas in the first space is higher than the temperature of the gas in the second space. Accordingly, the air-fuel mixture is self-ignited first in the first space, and then the air-fuel mixture is self-ignited in the second space. As a result, in a high-load operation region where the amount of fuel provided for combustion is large and the sound generated with combustion tends to be excessive, the sound generated with the heat energy generated by combustion is This can be reduced compared to the case of self-ignition and combustion.

  On the other hand, in the light load operation region, since the amount of fuel contained in the air-fuel mixture provided for combustion is small, the air-fuel mixture may not self-ignite. Therefore, in the light load operation region as described above, the air-fuel mixture can be reliably burned by performing the stratified spark ignition operation instead of the self-ignition operation.

In this case, the spark ignition operation execution means forms a homogeneous mixture by injecting the fuel by the fuel injection means in the first half of the compression stroke so that the fuel density in the first space is spatially uniform. And homogeneous spark ignition operation executing means for performing an operation by a homogeneous spark ignition system for igniting and burning the homogeneous mixture formed by the spark generated by the spark ignition means,
When the load of the internal combustion engine is an extremely high load equal to or greater than a predetermined extremely high load threshold greater than the high load threshold, the operation switching means is operated by the homogeneous spark ignition operation executing means of the spark ignition operation executing means. It is preferable to perform the operation.

  In the extremely high load operation region, since the amount of fuel contained in the air-fuel mixture supplied for combustion is large, when the self-ignition operation is performed, the sound generated with combustion may become excessive. Therefore, as in the above configuration, in the extremely high load operation region, by performing operation by the homogeneous spark ignition method (homogeneous spark ignition operation) instead of the self-ignition operation, noise generated with combustion is reduced. Can do.

  Further, during the homogeneous spark ignition operation, fuel is injected in the first half of the compression stroke. Thereby, the injected fuel is sufficiently diffused in the first space within the compression stroke period. As a result, a homogeneous air-fuel mixture having a spatially uniform fuel density is formed, so that unburned components contained in the combustion gas can be reduced and knocking can be prevented from occurring.

  In addition, during the homogeneous spark ignition operation, the air-fuel mixture in the first space that is compressed to a greater degree burns. Thereby, since an equal volume can be improved, a fuel consumption can be improved.

Further, the spark ignition operation execution means has the first fuel density in which the fuel density in the first space is spatially uniform, and the fuel density in the second space is spatially uniform. The fuel is injected by the fuel injection means so as to have a second fuel density lower than the fuel density of the fuel to form a homogeneous mixture in each of the first space and the second space. The homogeneous mixture formed in this way is ignited by the spark generated by the spark ignition means and burned, and the homogeneous mixture formed in the second space is generated by combustion in the first space. Including self-ignition-induced homogeneous spark ignition operation execution means for performing an operation by a self-ignition-induced homogeneous spark ignition method for self-ignition by compression and burning.
When the load of the internal combustion engine is a high load equal to or higher than a predetermined high load threshold, the internal combustion engine is operated by the self-ignition induced homogeneous spark ignition operation execution means of the spark ignition operation execution means, and the load of the internal combustion engine It is preferable to provide an operation switching means for causing the internal combustion engine to be operated by the stratified spark ignition operation executing means of the spark ignition operation executing means when is a light load smaller than the high load threshold.

  According to this, in the high load operation region, the homogeneous air-fuel mixture in the first space whose fuel density is the first fuel density is ignited by the spark and burned. Thereafter, when the piston moves from the predetermined position to the bottom dead center position side, the first space and the second space communicate with each other. At this time, the high-temperature and high-pressure combustion gas generated in the first space expands, so that the homogeneous air-fuel mixture in the second space whose fuel density is the second fuel density lower than the first fuel density. Compressed and heated. Thereby, the homogeneous air-fuel mixture in the second space is self-ignited and burned. As a result, the amount of NOx generated with combustion can be reduced as compared with the case where all fuels are burned by the homogeneous spark ignition system.

  Furthermore, another internal combustion engine according to the present invention includes a cylinder block in which a cylinder bore is formed, a cylinder head disposed at an upper portion of the cylinder block, a piston that reciprocates in the cylinder bore, at least a wall surface of the cylinder bore, Fuel injection means for injecting fuel into a combustion chamber constituted by the lower surface of the cylinder head and the top surface of the piston, spark ignition means for generating sparks in the combustion chamber, and air introduced into the combustion chamber A spark ignition method is performed in which an air-fuel mixture including the introduced air and the fuel injected by the fuel injection means is formed, and the air-fuel mixture formed is ignited by the spark generated by the spark ignition means and burned. Spark ignition operation execution means.

  The combustion chamber is divided into two spaces consisting of a first space and a second space that are independent from each other when the piston is on the top dead center position side from a predetermined position, and the piston is at the top dead center position. The first space volume ratio, which is the ratio of the volume of the first space when the piston is at the predetermined position to the volume of the first space, is the second space when the piston is at the top dead center position. The second space volume ratio, which is the ratio of the volume of the second space when the piston is at the predetermined position, is larger than the second space volume ratio.

The fuel injection means is disposed so as to face the second space.
The spark ignition means is arranged to face the second space.
The spark ignition operation execution means has a first uniform fuel density in which the fuel density, which is a spatial distribution density of fuel contained in the air-fuel mixture in the second space, is spatially uniform, and in the first space. The fuel is injected by the fuel injection means so that the fuel density becomes a second fuel density lower than the first fuel density, which is spatially uniform, in each of the first space and the second space. A homogeneous mixture is formed, and the homogeneous mixture formed in the second space is ignited by the spark generated by the spark ignition means and burned, and the homogeneous mixture formed in the first space is The piston is configured to be self-ignited and combusted by being compressed.

  As described above, since the first space volume ratio is larger than the second space volume ratio, the temperature of the air-fuel mixture in the first space is generated in the second space through the communication between the first space and the second space. Even if the gas mixture is not compressed and heated by the combustion gas, the mixture is compressed by the piston so that the temperature becomes sufficiently high.

  Therefore, as in the above configuration, the air-fuel mixture in the second space is burned by the homogeneous spark ignition method, and the air-fuel mixture in the first space is self-ignited and burned by compression of the piston, so that all the fuel is burned. The amount of NOx produced with combustion can be reduced compared with the case where combustion is performed by the homogeneous spark ignition system. Furthermore, the timing at which the air-fuel mixture in the first space is self-ignited and the timing at which the air-fuel mixture in the second space is ignited by a spark (before the piston is connected to the first space and the second space). The timing can be close to each other (when it is on the top dead center position side from the predetermined position). As a result, the equal volume can be improved, and the fuel efficiency can be improved.

  Further, another internal combustion engine according to the present invention includes a cylinder block in which a cylinder bore is formed, a cylinder head disposed at an upper portion of the cylinder block, a piston that reciprocates in the cylinder bore, at least a wall surface of the cylinder bore, Fuel injection means for injecting fuel into a combustion chamber constituted by the lower surface of the cylinder head and the top surface of the piston, spark ignition means for generating sparks in the combustion chamber, and air introduced into the combustion chamber A spark ignition method is performed in which an air-fuel mixture including the introduced air and the fuel injected by the fuel injection means is formed, and the air-fuel mixture formed is ignited by the spark generated by the spark ignition means and burned. Spark ignition operation execution means.

  The combustion chamber is divided into two spaces consisting of a first space and a second space that are independent from each other when the piston is on the top dead center position side from a predetermined position, and the piston is at the top dead center position. The first space volume ratio, which is the ratio of the volume of the first space when the piston is at the predetermined position to the volume of the first space, is the second space when the piston is at the top dead center position. The second space volume ratio, which is the ratio of the volume of the second space when the piston is at the predetermined position, is larger than the second space volume ratio.

  The spark ignition means includes first spark ignition means arranged so as to face the first space, and second spark ignition means arranged so as to face the second space.

  The spark ignition operation execution means causes the fuel injection means to distribute the fuel so that the fuel density in the second space is spatially uniform and the fuel density in the first space is spatially uniform. The second spark ignition means is injected to form a homogeneous mixture in each of the first space and the second space, and the homogeneous mixture formed in the second space is at a first spark ignition timing. Is ignited and burned by the sparks generated, and the first spark ignition is performed at the second spark ignition timing retarded from the first spark ignition timing with respect to the homogeneous mixture formed in the first space. The means is configured to be ignited and burned by the generated spark.

  Generally, in an internal combustion engine in which a spark ignition operation is performed, the generated heat energy generated per unit time by combustion is maximized by a spark so that the piston is maximized at a predetermined timing near the top dead center position. By determining the ignition timing (spark ignition timing), high thermal efficiency is achieved. By the way, the more the air-fuel mixture is compressed, the faster the flame propagates, so the time from the spark ignition timing to the timing at which the generated thermal energy becomes maximum (maximum thermal energy timing) is shortened.

  Accordingly, when the spark ignition timing is set to be equal to each other in the two spaces, the first space that is compressed to be larger and the second space that is compressed to be smaller, the maximum thermal energy timing in each of the two spaces is Since the timings are different from each other, there is a problem that the thermal efficiency is lowered.

  On the other hand, according to the above configuration, after the second spark ignition means generates a spark in the second space to be compressed smaller, the first spark ignition means generates the spark in the first space to be compressed more greatly. appear. Accordingly, the maximum thermal energy timing in each of the two spaces can be set to the predetermined timing that is close to each other. As a result, the thermal efficiency can be improved and the maximum output of the internal combustion engine can be improved.

In this case, air is introduced into the combustion chamber, and an air-fuel mixture including the introduced air, fuel injected by the fuel injection means, and combustion gas is formed in the combustion chamber, and the air-fuel mixture formed is compressed. Self-ignition operation execution means for performing operation by a premixed compression self-ignition method in which self-ignition is performed in the first space and the second space to burn
When the load of the internal combustion engine is smaller than a predetermined load threshold, the self-ignition operation execution means is operated to perform the operation of the internal combustion engine, and the load of the internal combustion engine is a load equal to or higher than the predetermined load threshold Operation switching means for operating the internal combustion engine by the spark ignition operation execution means;
Is preferably provided.

  According to this, in the high-load operation region, by performing the self-ignition operation, it is possible to improve the fuel efficiency and reduce the amount of NOx generated with combustion. Furthermore, as described above, since the first space volume ratio is larger than the second space volume ratio, the temperature of the air-fuel mixture in the first space becomes higher than the temperature of the air-fuel mixture in the second space. Accordingly, the air-fuel mixture is self-ignited first in the first space, and then the air-fuel mixture is self-ignited in the second space. As a result, in a high-load operation region where the amount of fuel provided for combustion is large and the sound generated with combustion tends to be excessive, the sound generated with the heat energy generated by combustion is This can be reduced compared to the case of self-ignition and combustion.

  On the other hand, in the extremely high load operation region, the amount of fuel used for combustion is larger than in the high load operation region. For this reason, when self-ignition operation is performed, the sound generated with combustion may become excessive. Therefore, in the extremely high load operation region as described above, excessive spark generation can be prevented by performing a spark ignition operation with a longer combustion period instead of the self-ignition operation.

(First embodiment)
Embodiments of an internal combustion engine according to the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of an internal combustion engine 10 according to the first embodiment. The internal combustion engine 10 is a multi-cylinder (4-cylinder) internal combustion engine that can be operated by switching between a 4-cycle spark ignition system and a 4-cycle premixed compression self-ignition system. FIG. 1 shows only a cross section of a specific cylinder, but the other cylinders have the same configuration.

  The internal combustion engine 10 supplies air to the cylinder block portion 20 including a cylinder block, a cylinder block lower case, an oil pan, and the like, a cylinder head portion 30 fixed on the cylinder block portion 20, and the cylinder block portion 20. The intake system 40 and the exhaust system 50 for releasing the exhaust gas from the cylinder block unit 20 to the outside are included.

  The cylinder block portion 20 includes a hollow cylindrical cylinder (cylinder bore) 21 having a central axis, a substantially columnar piston 22, a connecting rod 23, and a crankshaft 24. The piston 22 reciprocates in the cylinder 21, and the reciprocating motion of the piston 22 is transmitted to the crankshaft 24 through the connecting rod 23, whereby the crankshaft 24 rotates. A bore wall surface of the cylinder 21 (wall surface of the cylinder bore), a top surface of the piston 22 (piston head), and a lower surface of the cylinder head portion 30 form a combustion chamber 25.

  As shown in FIG. 2, the top surface of the piston 22 has a long distance in the central axis direction of the cylinder 21 from the reference position (for example, crank pin position or lower end portion) of the piston 22 to the top surface of the piston 22. It consists of a high-part upper surface 22a and a piston low-part upper surface 22b having a short distance.

  The upper surface 22a of the piston high portion is configured to coincide with one of two semicircles obtained by dividing the circle formed by the top surface of the piston 22 into two in a front view. The piston lower part upper surface 22b is configured to coincide with the other of the two semicircles in a front view. Between the piston upper portion upper surface 22a and the piston lower portion upper surface 22b, there is a piston top vertical wall surface 22c constituting a plane orthogonal to the plane orthogonal to the central axis of the cylinder 21 and including the central axis. Is formed.

  A piston high portion ring groove is formed in the side surface of the piston 22 and the piston top vertical wall surface 22c at a position in the vicinity of the piston high portion upper surface 22a. A piston high portion ring 22a1 is mounted in the piston high portion ring groove. The piston high portion ring 22a1 is made of a resin mainly composed of carbon. As will be described later, the piston high portion ring 22a1 increases the airtightness of each space during the period in which the combustion chamber 25 is divided into two spaces. Further, the piston high portion ring 22a1 prevents the central axis of the piston 22 from being inclined with respect to the central axis of the cylinder 21 (swing of the piston 22) during the same period.

  Further, three ring grooves are formed on the side surface of the piston 22 at a position in the vicinity of the lower piston upper surface 22b between the lower piston upper surface 22b and the lower end of the piston 22. Piston rings 22d are mounted in these ring grooves, respectively.

  The piston ring 22d is made of steel or cast iron. The piston ring 22d enhances the airtightness of the combustion chamber 25 and scrapes down an excess oil film formed on the bore wall surface of the cylinder 21 downward.

  Referring again to FIG. 1, the cylinder head unit 30 serves as an intake port 31 that communicates with the combustion chamber 25, an intake valve 32 that opens and closes the intake port 31, and an intake valve drive unit that drives the intake valve 32. An intake valve drive mechanism 32a, an exhaust port 33 communicating with the combustion chamber 25, an exhaust valve 34 for opening and closing the exhaust port 33, an exhaust valve drive mechanism 34a as an exhaust valve drive means for driving the exhaust valve 34, an ignition plug 35, an ignition plug An igniter 36 including an ignition coil that generates a high voltage to be applied to 35 and a fuel injection valve (fuel injection means) 37 that directly injects fuel into the combustion chamber 25 are provided. The intake valve drive mechanism 32a and the exhaust valve drive mechanism 34a are connected to a drive circuit 38.

  As shown in FIG. 2, the lower surface of the cylinder head portion 30 is the same as the lower surface 30a of the cylinder head that has a long distance in the central axis direction of the cylinder 21 from the reference position of the piston 22 to the lower surface of the cylinder head portion 30. The cylinder head lower portion lower surface 30b has a short distance.

  The cylinder head high portion lower surface 30a is obtained by dividing a circle formed by a cross section of the cylinder 21 by a plane orthogonal to the central axis of the cylinder 21 into two parts by a plane including the piston top vertical wall surface 22c in a front view. It corresponds to one of the two semicircles facing the piston upper surface 22a. The cylinder head lower portion lower surface 30b matches the other of the two semicircles in a front view.

  The cylinder head lower portion lower surface 30b is formed so as to form a plane existing in the plane formed by the piston high portion upper surface 22a when the rotation angle (crank angle) of the crankshaft 24 is BTDC 90 °. BTDC is a crank angle with the top dead center (TDC) as the origin and the direction opposite to the rotation direction of the crankshaft 24 taken positively. In the present specification, the position of the piston 22 when the crank angle is BTDC 90 ° is referred to as a combustion chamber divided piston position.

  In the cylinder head high portion lower surface 30a, the distance L1 between the cylinder head high portion lower surface 30a and the cylinder head lower portion lower surface 30b is larger than the distance L2 between the piston high portion upper surface 22a and the piston lower portion upper surface 22b. It is formed as follows.

  Between the cylinder head high portion lower surface 30a and the cylinder head lower portion lower surface 30b, a cylinder head vertical wall surface 30c that forms a plane parallel to the piston top vertical wall surface 22c and includes the central axis of the cylinder 21. Is formed.

  Here, refer to FIG. 3 for the change of the combustion chamber 25 (the space formed by the bore wall surface of the cylinder 21, the top surface of the piston 22 and the lower surface of the cylinder head 30) with respect to the change of the crank angle (movement of the piston 22). While adding explanation.

  When the crank angle is BTDC 180 ° (when the piston 22 is at the bottom dead center position BDC), as shown in FIG. 3A, the bore wall surface of the cylinder 21, the piston upper surface 22a, and the piston lower surface Combustion chamber 25 as one independent space is constituted by 22b, piston top vertical wall surface 22c, cylinder head high portion lower surface 30a, cylinder head low portion lower surface 30b and cylinder head vertical wall surface 30c.

  On the other hand, when the crank angle is BTDC 90 ° (when the piston 22 is at the combustion chamber split piston position), as shown in FIG. 3B, the bore wall surface of the cylinder 21, the piston upper portion upper surface 22a, The cylinder head high portion lower surface 30a and the cylinder head vertical wall surface 30c constitute a high combustion chamber 25a (second space) as one independent space. Further, a lower combustion chamber 25b (first space) as an independent space is formed by the bore wall surface of the cylinder 21, the piston lower portion upper surface 22b, the cylinder head lower portion lower surface 30b, and the piston top vertical wall surface 22c. Is configured.

  As described above, when the piston 22 is located at the top dead center position side (cylinder head portion 30 side) from the combustion chamber division piston position which is a predetermined position, the piston top vertical wall surface 22c and the cylinder head vertical wall surface 30c are mutually connected. By facing each other, a high combustion chamber 25a (second space) and a low combustion chamber 25b (first space) are formed as two independent spaces.

  By the way, the volume VH0 of the high combustion chamber 25a and the volume VL0 of the low combustion chamber 25b when the piston 22 is at the combustion chamber division piston position are the respective spaces in the state where the combustion chamber 25 is divided into two spaces. The maximum volume at.

  Further, when the crank angle is BTDC 0 ° (when the piston 22 is at the top dead center position TDC), as shown in FIG. 3C, the volume VH1 of the high combustion chamber 25a and the low combustion chamber 25b. The volume VL1 is the minimum volume in each space.

  With the above-described configuration, in this example, the lower combustion chamber 25b when the piston 22 is at the combustion chamber split piston position with respect to the volume VL1 of the lower combustion chamber 25b when the piston 22 is at the top dead center position. The lower combustion chamber volume ratio (first space volume ratio) VL0 / VL1, which is the ratio of the volume VL0, is the same as that of the piston 22 relative to the volume VH1 of the higher combustion chamber 25a when the piston 22 is at the top dead center position. It is larger than the high combustion chamber volume ratio (second space volume ratio) VH0 / VH1, which is the ratio of the volume VH0 of the high combustion chamber 25a at the combustion chamber division piston position.

  Therefore, when the gas in the combustion chamber 25 is compressed as the piston 22 moves from the combustion chamber division piston position to the top dead center position, the gas in the low combustion chamber 25b is larger than the gas in the high combustion chamber 25a. Compressed to a higher temperature.

  The intake port 31 is formed to open at two locations in the cylinder head lower portion lower surface 30b as shown in FIG. 4 when the lower surface of the cylinder head portion 30 is viewed from the combustion chamber 25 side. Accordingly, the cylinder head portion 30 is provided with two intake valves 32. Each intake valve 32 opens and closes the opening of each intake port 31. When the opening of the intake port 31 is opened by the intake valve 32, the intake port 31 communicates with the combustion chamber 25 (in the period when the combustion chamber 25 is divided into two spaces, the lower combustion chamber 25b). When closed by the valve 32, the combustion chamber 25 is shut off.

  The exhaust port 33 is formed so as to open at two locations in the cylinder head high portion lower surface 30a. Accordingly, the cylinder head portion 30 is provided with two exhaust valves 34. Each exhaust valve 34 opens and closes the opening of each exhaust port 33. When the opening of the exhaust port 33 is opened by the exhaust valve 34, the exhaust port 33 communicates with the combustion chamber 25 (in the period when the combustion chamber 25 is divided into two spaces, the higher combustion chamber 25a), and the opening is exhausted. When closed by the valve 34, the combustion chamber 25 is shut off.

  The spark plug 35 is disposed in the cylinder head portion 30 at a position between the two intake ports 31 (therefore, the two intake valves 32). The spark plug 35 includes a tip portion that generates a spark (ignition spark), and the tip portion serves as a combustion chamber 25 (in the period when the combustion chamber 25 is divided into two spaces, the lower combustion chamber 25b). It has come to be exposed.

  As shown in FIGS. 1, 2 and 4, the fuel injection valve 37 is a side wall surface of the combustion chamber 25 on the side of the lower surface 30b of the cylinder head lower portion, and is orthogonal to the plane formed by the cylinder head vertical wall surface 30c. And it is arrange | positioned in the position on the straight line which passes the center axis line of the cylinder 21. As shown in FIG. The fuel injection valve 37 includes a front end portion that injects fuel toward substantially the center of the combustion chamber 25, and the front end portion is the combustion chamber 25 (in the period in which the combustion chamber 25 is divided into two spaces, the lower portion). It is exposed to the combustion chamber 25b). The fuel in the fuel tank (not shown) is supplied to the fuel injection valve 37 by a fuel pressure adjusting means (not shown) and a fuel pump.

  With such a configuration, when fuel is injected from the fuel injection valve 37, if the position of the piston 22 is on the top dead center position side, the injected fuel is blocked by the piston top vertical wall surface 22c, and the upper surface of the piston high portion It becomes difficult to reach the space above 22a. In other words, the amount of fuel that reaches the space above the piston upper surface 22a increases as the position of the piston 22 at the fuel injection timing (fuel injection timing) is closer to the bottom dead center position.

  Referring again to FIG. 1, the intake system 40 includes an intake manifold 41 that communicates with the intake port 31, a surge tank 42 that communicates with the intake manifold 41, and one end connected to the surge tank 42. An intake duct 43 that forms an intake passage with the tank 42; an air filter 44 that is disposed in the intake duct 43 in order from the other end of the intake duct 43 to the downstream (surge tank 42); a compressor 91a of the supercharger 91; An intercooler 45 and a throttle valve 46 are provided.

  The intercooler 45 is water-cooled and cools the air passing through the intake duct 43. The intercooler 45 discharges heat of the cooling water in the intercooler 45 to the atmosphere by a radiator and a circulation pump (not shown).

  The throttle valve 46 is rotatably supported by the intake duct 43 and is driven by a throttle valve actuator 46a so that the opening cross-sectional area of the intake passage is variable.

  The exhaust system 50 includes an exhaust pipe 51 including an exhaust manifold that communicates with the exhaust port 33 and forms an exhaust passage together with the exhaust port 33, a turbine 91b of a supercharger 91 disposed in the exhaust pipe 51, and a downstream of the turbine 91b. The exhaust pipe 51 is provided with a catalyst device 52.

  With such an arrangement, the turbine 91b of the supercharger 91 is rotated by the energy of the exhaust gas. Further, the turbine 91b is connected to the compressor 91a of the intake system 40 via a shaft. Thus, the compressor 91a of the intake system 40 rotates integrally with the turbine 91b to compress the air in the intake passage. That is, the supercharger 91 supercharges air to the internal combustion engine 10 using the energy of the exhaust gas.

  On the other hand, this system includes an electric control device 70. The electric control device 70 is a microcomputer including a CPU, a ROM, a RAM, an interface, and the like (all not shown). A crank position sensor 61 that detects an engine rotational speed NE from a rotational speed of the crankshaft 24 and an accelerator opening sensor 62 that detects an accelerator pedal operation amount Accp (not shown) are connected to the electric control device 70. . The electric control device 70 inputs each detection signal from these sensors. Furthermore, the electric control device 70 is connected to the igniter 36, the fuel injection valve 37, the drive circuit 38, and the throttle valve actuator 46a of each cylinder. The electric control device 70 sends drive signals to these.

  As shown in FIG. 5, the internal combustion engine 10 constitutes a part of a stratified spark ignition operation execution means F11, a self-ignition operation execution means F12, and a part of a spark ignition operation execution means that constitute a part of the spark ignition operation execution means. Including homogeneous spark ignition operation execution means F13 and operation switching means G11. The functions of these means are achieved by the CPU of the electric control device 70 executing a predetermined program. Therefore, hereinafter, various operations by the CPU will be described as being performed by the respective means.

  The operation switching means G11 stores the operation region map shown in FIG. 6 in the ROM of the electric control device 70. The operation region map is a map that defines the relationship between the load of the internal combustion engine 10 and the engine rotation speed (rotation speed) NE and the operation method.

  In this operation region map, a stratified spark ignition method, a premixed compression auto-ignition method, and a homogeneous spark ignition method are designated as operation methods. In this operation region map, the stratified spark ignition operation region A, which is the operation region in which the stratified spark ignition method is designated, is a load region that is smaller than a predetermined high load threshold in the entire operation region.

  Furthermore, the self-ignition operation region B, which is an operation region in which the premixed compression self-ignition method is designated, is a region of a load that is equal to or higher than the high load threshold (a region on the higher load side than the stratified spark ignition operation region A). Thus, the load region is smaller than a predetermined extremely high load threshold value that is larger than the high load threshold value. In addition, the homogeneous spark ignition operation region C, which is an operation region in which the homogeneous spark ignition method is specified, is a load region (region on the higher load side than the self-ignition operation region B) of the above-mentioned extremely high load threshold. .

  The operation switching means G11 determines an operation method based on the operation region map, the load of the internal combustion engine 10 and the engine rotation speed NE, and performs the operation using the determined operation method. The load of the internal combustion engine 10 may be the required torque Tqtgt determined based on the accelerator pedal operation amount Accp and the engine rotational speed NE, or simply the accelerator pedal operation amount Accp.

(When the internal combustion engine 10 is operated in the stratified spark ignition operation region A)
When the internal combustion engine 10 is operated in the stratified spark ignition operation region A (during stratified spark ignition operation), the operation switching means G11 selects the stratified spark ignition operation execution means F11 according to the operation region map. Thereby, the internal combustion engine 10 is operated by the stratified spark ignition operation execution means F11.

  The stratified spark ignition operation execution means F11 performs fuel from the fuel injection valve 37 in the lower combustion chamber 25b so that the spatial distribution density (fuel density) of fuel is higher in the region near the spark plug 35 than in other regions. Is injected to form a stratified mixture, and the formed stratified mixture is ignited by a spark generated by the spark plug 35 and burned. More specifically, the stratified spark ignition operation execution means F11 operates the intake valve drive mechanism 32a, the exhaust valve drive mechanism 34a, the ignition plug 35, and the fuel injection valve 37, respectively, as shown in FIG. The engine 10 is operated.

  First, the stratified spark ignition operation execution means F11 drives the exhaust valve drive mechanism 34a to open the exhaust valve 34 at the spark ignition exhaust valve opening timing EO corresponding to the load of the internal combustion engine 10 (( See 1).). Thereby, exhaust of the combustion gas produced | generated by the combustion in the last combustion cycle starts. Next, the stratified spark ignition operation execution means F11 drives the exhaust valve drive mechanism 34a to close the exhaust valve 34 at the spark ignition exhaust valve closing timing EC corresponding to the load of the internal combustion engine 10 (( See 2).). Thereby, exhaust ends.

  Thereafter, the stratified spark ignition operation execution means F11 drives the intake valve drive mechanism 32a to open the intake valve 32 at the spark ignition intake valve opening timing IO corresponding to the load of the internal combustion engine 10 (( See 3).). Thereby, inhalation is started. Thus, the negative overlap period which is a period from the time when exhaust ends to the time when intake starts is provided. During stratified spark ignition operation, the combustion gas to be included in the air-fuel mixture is not required as in the self-ignition operation described later, so the negative overlap period is set to be shorter than the same period during self-ignition operation. The

  Then, the stratified spark ignition operation execution means F11 drives the intake valve drive mechanism 32a to close the intake valve 32 at the spark ignition intake valve closing timing IC corresponding to the load of the internal combustion engine 10 (( See 4).). The spark ignition intake valve closing timing IC is set to be on the more retarded side than the self-ignition intake valve closing timing IC, which will be described later, in order to avoid knocking that tends to occur when the air-fuel mixture is greatly compressed. Is done. As a result, the intake air is finished and the compression of the air introduced into the combustion chamber 25 is started.

  Thereafter, at the timing when the crank angle becomes BTDC 90 ° (the position of the piston 22 becomes the combustion chamber division piston position), the combustion chamber 25 is divided into two spaces consisting of a high combustion chamber 25a and a low combustion chamber 25b. The

  Next, the stratified spark ignition operation execution means F11 opens the fuel injection valve 37, so that the second half of the compression stroke in which the crank angle becomes BTDC 45 ° (at least the spark ignition intake valve closing timing IC and the piston 22 The fuel is injected at θinj (timing indicated by a one-dot broken line marked with A in FIG. 7) at a timing that is retarded from the timing intermediate between the timing at which the position becomes the top dead center position ((5) reference.). The amount of fuel injected at this time is based on the load of the internal combustion engine 10 and the engine speed NE so that the air-fuel ratio of the air-fuel mixture in the lower combustion chamber 25b becomes a lean air-fuel ratio (lean air-fuel ratio). It is an amount determined.

  At this time, as described above, the combustion chamber 25 is divided into two spaces including a high combustion chamber 25a and a low combustion chamber 25b. Therefore, as shown in FIG. 8A, the injected fuel stays in the vicinity of the piston top vertical wall surface 22c. Thus, more fuel can be collected in the region near the spark plug 35 than in the case where the combustion chamber 25 is not divided into two spaces. As a result, the region where the stratified spark ignition operation can be performed in the light load operation region where the amount of fuel contained in the air-fuel mixture supplied for combustion is small can be expanded, and the fuel efficiency can be improved.

  After that, when the crank angle becomes BTDC 30 °, as shown in FIG. 8B, a stratified mixture is formed in the lower combustion chamber 25b in the region near the spark plug 35 as compared with the other regions. Is done.

  Then, the stratified spark ignition operation execution means F11 generates a spark from the tip of the spark plug 35 at the spark ignition timing θig at which the position of the piston 22 is in the vicinity of the top dead center position, and enters the lower combustion chamber 25b. The stratified mixture is ignited by sparks (by spark ignition) and combusted (see (6)). At this time, the stratified spark ignition operation execution means F11 determines the spark ignition timing θig based on the load of the internal combustion engine 10 and the engine speed NE.

  Thus, the air-fuel mixture can be reliably burned in the lower combustion chamber 25b (first space) where the gas temperature becomes higher. Furthermore, since the time between the fuel injection timing θinj in the latter half of the compression stroke and the spark ignition timing θig is extremely short, the fuel density of the stratified mixture becomes spatial due to the diffusion of the fuel contained in the formed stratified mixture. The homogenous mixture can be ignited before it becomes uniform. As a result, the stratified spark ignition operation can be performed more reliably even in an extremely light load operation region where the amount of fuel contained in the air-fuel mixture provided for combustion is small.

Thereafter, gas expansion accompanying combustion by spark ignition begins.
In this way, in the stratified spark ignition operation region A, the internal combustion engine 10 is stratified spark ignition operated.

(When the internal combustion engine 10 is operated in the self-ignition operation region B)
On the other hand, when the internal combustion engine 10 is operated in the self-ignition operation region B (at the time of self-ignition operation), the operation switching means G11 selects the self-ignition operation execution means F12 according to the operation region map. Thereby, the internal combustion engine 10 is operated by the self-ignition operation execution means F12.

  The self-ignition operation execution means F12 combusts the homogeneous mixture containing the air introduced into the combustion chamber 25 and the fuel and the combustion gas injected from the fuel injection valve 37 so that the fuel density is spatially uniform. The homogeneous mixture formed in the chamber 25 is compressed by the piston 22 and is ignited and combusted in the high combustion chamber 25a and the low combustion chamber 25b. More specifically, the self-ignition operation execution means F12 operates the internal combustion engine 10 by operating the intake valve drive mechanism 32a, the exhaust valve drive mechanism 34a, and the fuel injection valve 37, respectively, as shown in FIG. Do.

  First, the self-ignition operation execution means F12 opens the exhaust valve 34 at the self-ignition exhaust valve opening timing EO corresponding to the load of the internal combustion engine 10 by driving the exhaust valve drive mechanism 34a ((1 ). Thereby, exhaust of the combustion gas produced | generated by the combustion in the last combustion cycle starts. Next, the self-ignition operation execution means F12 drives the exhaust valve drive mechanism 34a to close the exhaust valve 34 at the self-ignition exhaust valve closing timing EC corresponding to the load of the internal combustion engine 10 ((2 ). Thereby, exhaust ends.

  Thereafter, the self-ignition operation execution means F12 drives the intake valve drive mechanism 32a to open the intake valve 32 at the self-ignition intake valve opening timing IO corresponding to the load of the internal combustion engine 10 ((3 ). Thereby, inhalation is started. During self-ignition operation, the combustion gas to be included in the air-fuel mixture requires more combustion gas than during stratified spark ignition operation, so the negative overlap period is set longer than the same period during stratified spark ignition operation. The For this reason, the self-ignition intake valve opening timing IO is set to be retarded from the spark ignition intake valve opening timing IO. As a result, a larger amount of combustion gas remains in the combustion chamber 25 than in the stratified spark ignition operation.

  Next, the self-ignition operation execution means F12 drives the intake valve drive mechanism 32a to close the intake valve 32 at the self-ignition intake valve closing timing IC corresponding to the load of the internal combustion engine 10 (( See 4).). As a result, the intake air is finished, and the compression of the gas composed of air and combustion gas is started.

  Then, the self-ignition operation execution means F12 opens the fuel injection valve 37 so that the first half of the compression stroke in which the crank angle becomes BTDC 135 ° (at least the positions of the self-ignition intake valve closing timing IC and the piston 22 are The fuel is injected at a timing θinj that is an advance side from the timing intermediate between the timing of the top dead center position (see (5)). The amount of fuel injected at this time is based on the load of the internal combustion engine 10 and the engine speed NE so that the air-fuel ratio of the air-fuel mixture in the combustion chamber 25 becomes a very lean air-fuel ratio (ultra-lean air-fuel ratio). It is an amount determined.

  At this time, the distance between the upper end portion of the piston top vertical wall surface 22c and the lower end portion of the cylinder head vertical wall surface 30c is relatively large. Therefore, as shown in FIG. 10A, substantially half of the injected fuel stays in the space above the piston lower surface 22b by being blocked by the piston top vertical wall surface 22c. On the other hand, the remaining approximately half of the injected fuel reaches the space above the piston upper surface 22a.

  Thereafter, as shown in FIG. 10B, at the timing when the crank angle becomes BTDC 90 ° (the position of the piston 22 becomes the combustion chamber split piston position), the combustion chamber 25 is separated from the high combustion chamber 25a and the low combustion chamber 25a. It is divided into two spaces consisting of partial combustion chambers 25b. Thereby, in the high combustion chamber 25a and the low combustion chamber 25b, an air-fuel mixture (air-fuel mixture in which the air-fuel ratio is an ultra lean air-fuel ratio) having a spatially uniform fuel density and substantially the same fuel density. Each is formed.

  When the piston 22 approaches the top dead center position, the air-fuel mixture in the lower combustion chamber 25b, which is compressed to a greater extent, quickly reaches a high temperature state, and is thus ignited earlier than the air-fuel mixture in the high combustion chamber 25a. . Thereafter, when the piston 22 further approaches the top dead center position, the air-fuel mixture is self-ignited in the high combustion chamber 25a.

  A curve C1 indicated by a solid line in FIG. 11 shows a change in generated heat energy with respect to the crank angle when such an operation is performed. The generated heat energy is heat energy generated per unit time by combustion of the air-fuel mixture. As shown by this curve C1, the generated heat energy has two peaks at different crank angles: a peak due to combustion in the low combustion chamber 25b and a peak due to combustion in the high combustion chamber 25a. It changes to have each.

  As a result, the magnitude of the impact force per unit time caused by the thermal energy generated by the combustion of the piston 22, the cylinder block portion 20, the cylinder head portion 30, and the like constituting the combustion chamber 25 is determined in the combustion chamber 25. This is smaller than when the air-fuel mixture is self-ignited and burned at a time (within a very short period of time) (see the curve C2 shown by the broken line in FIG. 11). As a result, it is possible to reduce noise generated with the same impact that tends to be excessive in the high-load operation region.

Thereafter, gas expansion accompanying combustion by self-ignition begins.
In this way, in the self-ignition operation region B, the internal combustion engine 10 is self-ignited. Thereby, while being able to make a fuel consumption favorable, the quantity of NOx produced | generated with combustion can be reduced.

(When the internal combustion engine 10 is operated in the homogeneous spark ignition operation region C)
When the internal combustion engine 10 is operated in the homogeneous spark ignition operation region C (during homogeneous spark ignition operation), the operation switching means G11 selects the homogeneous spark ignition operation execution means F13 according to the operation region map. Thereby, the internal combustion engine 10 is operated by the homogeneous spark ignition operation execution means F13.

  The homogeneous spark ignition operation execution means F13 injects the fuel from the fuel injection valve 37 so that the spatial distribution density (fuel density) of the fuel is spatially uniform in the lower combustion chamber 25b, thereby generating a homogeneous mixture. The homogeneous mixture thus formed is ignited and burned by the spark generated by the spark plug 35. The homogeneous spark ignition operation execution means F13 differs from the stratified spark ignition operation execution means F11 only in that the timing at which fuel is injected is advanced. Therefore, the following description will focus on such differences.

  The homogeneous spark ignition operation execution means F13 closes the intake valve 32, thereby completing the intake stroke and starting the compression of the air, and the first half of the compression stroke in which the crank angle becomes BTDC 100 ° (at least the spark). Timing of the intake intake valve closing timing IC and the timing at which the position of the piston 22 is advanced between the timing at which the position of the piston 22 is at the top dead center position (timing indicated by the one-dot broken line with C in FIG. 7) At θinj, the fuel injection valve 37 is opened to inject fuel (see (5)). The amount of fuel injected at this time is an amount determined based on the load of the internal combustion engine 10 and the engine speed NE so that the air-fuel ratio of the air-fuel mixture in the lower combustion chamber 25b is the stoichiometric air-fuel ratio.

  At this time, the upper end portion of the piston top vertical wall surface 22c substantially reaches the lower end portion of the cylinder head vertical wall surface 30c. Therefore, as shown in FIG. 12A, the injected fuel stays in the space above the piston lower portion upper surface 22b by being blocked by the piston top vertical wall surface 22c.

  Thereafter, at the timing when the crank angle becomes BTDC 90 ° (the position of the piston 22 becomes the combustion chamber division piston position), the combustion chamber 25 is divided into two spaces consisting of a high combustion chamber 25a and a low combustion chamber 25b. The

  Next, when the crank angle reaches BTDC 30 °, as shown in FIG. 12B, a homogeneous mixture having a uniform fuel density in the mixture is formed in the lower combustion chamber 25b. . Thus, the injected fuel is sufficiently diffused in the lower combustion chamber 25b during the compression stroke. As a result, unburned components contained in the combustion gas can be reduced and knocking can be prevented from occurring.

  Then, the homogeneous spark ignition operation execution means F13 generates a spark from the tip of the spark plug 35 at the spark ignition timing θig at which the position of the piston 22 is in the vicinity of the top dead center position, and enters the lower combustion chamber 25b. Then, the air-fuel mixture is ignited by sparks (by spark ignition) and burned (see (6)). At this time, the homogeneous spark ignition operation execution means F13 determines the spark ignition timing θig based on the load of the internal combustion engine 10 and the engine speed NE.

  In this way, the air-fuel mixture in the lower combustion chamber 25b (first space) that is compressed more is combusted. Thereby, since the air-fuel mixture burns under a substantially high compression ratio, the isovolume can be improved. As a result, fuel consumption can be improved.

  In this manner, in the homogeneous spark ignition operation region C, the internal combustion engine 10 is subjected to the homogeneous spark ignition operation. As a result, it is possible to prevent the generation of excessive noise compared to the case where the self-ignition operation is performed.

  As described above, in the first embodiment of the internal combustion engine according to the present invention, when the piston is on the top dead center position side with respect to the combustion chamber division piston position, the high combustion chamber 25a and the low combustion chamber 25 are separated from each other. It is configured to be divided into two spaces consisting of partial combustion chambers 25b. Thereby, in the period when the combustion chamber 25 is divided | segmented, the area | region which can diffuse the fuel in the low part combustion chamber 25b becomes narrow compared with the case where a combustion chamber is not divided | segmented into two spaces.

  Furthermore, the first embodiment includes a fuel injection valve 37 and a spark plug 35 disposed so as to face the low combustion chamber 25b, and fuel is injected by the fuel injection valve 37 in the latter half of the compression stroke. A stratified mixture is formed in the combustion chamber 25b. As described above, more fuel can be collected in the region near the spark plug 35. As a result, the region where the stratified spark ignition operation can be performed in the light load operation region where the amount of fuel contained in the air-fuel mixture supplied for combustion is small can be expanded, and the fuel efficiency can be improved.

  In addition, in the first embodiment, the lower combustion chamber 25b when the piston 22 is at the same combustion chamber divided piston position with respect to the volume VL1 of the lower combustion chamber 25b when the piston 22 is at the top dead center position. The ratio of the volume VL0 (first space volume ratio) VL0 / VL1 is determined when the piston 22 is at the combustion chamber divided piston position with respect to the volume VH1 of the high combustion chamber 25a when the piston 22 is at the top dead center position. It is configured to be larger than the ratio of the volume VH0 (second space volume ratio) VH0 / VH1 of the high combustion chamber 25a.

  Thereby, the temperature of the air-fuel mixture in the lower combustion chamber 25b becomes higher than the temperature of the air-fuel mixture in the higher combustion chamber 25a. As a result, the air-fuel mixture can be reliably burned in the lower combustion chamber 25b even in the extremely light load operation region.

(Second Embodiment)
Next, an internal combustion engine according to a second embodiment of the present invention will be described. The internal combustion engine according to the second embodiment is different from the internal combustion engine according to the first embodiment in that self-ignition induced homogeneous spark ignition operation is performed in a high load operation region and an extremely high load operation region. Hereinafter, this difference will be mainly described.

  As shown in FIG. 13, the internal combustion engine 10 includes a stratified spark ignition operation execution means F21 that constitutes a part of the spark ignition operation execution means, and a self-ignition induced homogeneous spark ignition that constitutes a part of the spark ignition operation execution means. It includes means such as operation execution means F22 and operation switching means G21. The functions of these means are achieved by the CPU of the electric control device 70 executing a predetermined program. Therefore, hereinafter, various operations by the CPU will be described as being performed by the respective means.

  The operation switching means G21 stores the operation region map shown in FIG. 14 in the ROM of the electric control device 70. The operation region map is a map that defines the relationship between the load of the internal combustion engine 10 and the engine rotation speed (rotation speed) NE and the operation method.

  In this operation region map, a stratified spark ignition method and a self-ignition induced homogeneous spark ignition method are designated as operation methods. In this operation region map, the stratified spark ignition operation region A, which is the operation region in which the stratified spark ignition method is designated, is a load region that is smaller than a predetermined high load threshold in the entire operation region. Further, the self-ignition-induced homogeneous spark ignition operation region B, which is an operation region in which the self-ignition-induced homogeneous spark ignition method is designated, is a region of a load that is higher than the high load threshold value (a higher load side than the stratified spark ignition operation region A). Area).

  The operation switching means G21 determines an operation method based on the operation region map, the load of the internal combustion engine 10 and the engine rotational speed NE, and performs operation according to the determined operation method. The load of the internal combustion engine 10 may be the required torque Tqtgt determined based on the accelerator pedal operation amount Accp and the engine rotational speed NE, or simply the accelerator pedal operation amount Accp.

(When the internal combustion engine 10 is operated in the stratified spark ignition operation region A)
When the internal combustion engine 10 is operated in the stratified spark ignition operation region A (during stratified spark ignition operation), the operation switching means G21 selects the stratified spark ignition operation execution means F21 according to the operation region map. Thereby, the internal combustion engine 10 is operated by the stratified spark ignition operation execution means F21.

  The stratified spark ignition operation executing means F21 is the same as the stratified spark ignition operation executing means F11 included in the internal combustion engine according to the first embodiment. Therefore, the stratified spark ignition operation execution means F21 operates the internal combustion engine 10 by operating the intake valve drive mechanism 32a, the exhaust valve drive mechanism 34a, the ignition plug 35, and the fuel injection valve 37, respectively, as shown in FIG. Do. Thereby, in the stratified spark ignition operation region A, the internal combustion engine 10 is stratified spark ignition operated.

(When the internal combustion engine 10 is operated in the self-ignition induced homogeneous spark ignition operation region B)
On the other hand, when the internal combustion engine 10 is operated in the self-ignition induced homogeneous spark ignition operation region B (at the time of self-ignition induced homogeneous spark ignition operation), the operation switching means G21 executes the self-ignition induced homogeneous spark ignition operation according to the operation region map. The means F22 is selected. Thereby, the internal combustion engine 10 is operated by the self-ignition induced homogeneous spark ignition operation execution means F22.

  The self-ignition induced homogeneous spark ignition operation execution means F22 has a first uniform fuel density in the low combustion chamber 25b and a uniform fuel density in the high combustion chamber 25a. The fuel is injected from the fuel injection valve 37 so that the second fuel density is lower than the first fuel density, and a homogeneous mixture is formed in each of the high combustion chamber 25a and the low combustion chamber 25b. Further, the self-ignition induced homogeneous spark ignition operation execution means F22 ignites and burns the homogeneous air-fuel mixture formed in the lower combustion chamber 25b by the spark generated by the spark plug 35, and also the same high combustion chamber 25a. The combustion gas generated by the combustion in the lower combustion chamber 25b is compressed to be self-ignited and combusted.

  The self-ignition induced homogeneous spark ignition operation execution means F22 is different from the homogeneous spark ignition operation execution means F13 included in the internal combustion engine according to the first embodiment only in that the timing for injecting fuel is advanced. Therefore, more specific description will be given below centering on such differences.

  The self-ignition induced homogeneous spark ignition operation execution means F22 closes the intake valve 32, thereby completing the intake air and starting the compression of the air, and the timing at which the crank angle becomes BTDC 110 ° (FIG. 15). The fuel is injected by opening the fuel injection valve 37 (see timing (5)) at θinj (timing indicated by a one-dot broken line with B). The amount of fuel injected at this time is such that the air-fuel ratio in the lower combustion chamber 25b is the stoichiometric air-fuel ratio and the air-fuel ratio in the higher combustion chamber 25a is very lean. The amount is determined based on the load of the internal combustion engine 10 and the engine speed NE.

  At this time, the distance between the upper end portion of the piston top vertical wall surface 22c and the lower end portion of the cylinder head vertical wall surface 30c is considerably small. Accordingly, as shown in FIG. 16A, most of the injected fuel stays in the space above the piston lower portion upper surface 22b by being blocked by the piston top vertical wall surface 22c. The remaining small amount of fuel reaches the space above the piston upper surface 22a.

  Thereafter, as shown in FIG. 16B, at the timing when the crank angle becomes BTDC 90 ° (the position of the piston 22 becomes the combustion chamber split piston position), the combustion chamber 25 is separated from the high combustion chamber 25a and the low combustion chamber 25a. It is divided into two spaces consisting of partial combustion chambers 25b. As a result, in the lower combustion chamber 25b, a homogeneous mixture (homogeneous mixture whose air-fuel ratio is the stoichiometric air-fuel ratio) having the first fuel density in which the fuel density is spatially uniform is formed, and high In the partial combustion chamber 25a, a homogeneous mixture (homogeneous mixture in which the air-fuel ratio is an ultra lean air-fuel ratio) having a second fuel density lower than the first fuel density in which the fuel density is spatially uniform is formed. Is done.

  Then, the self-ignition induced homogeneous spark ignition operation execution means F22 generates a spark from the tip of the spark plug 35 at the spark ignition timing θig where the position of the piston 22 is in the vicinity of the top dead center position, and the low part combustion The homogeneous air-fuel mixture in the chamber 25b is ignited by sparks (by spark ignition) and combusted (see (6)). At this time, the self-ignition induced homogeneous spark ignition operation execution means F22 determines the spark ignition timing θig based on the load of the internal combustion engine 10 and the engine speed NE.

  Next, when the piston 22 moves from the combustion chamber division piston position to the bottom dead center position side, the high combustion chamber 25a and the low combustion chamber 25b communicate with each other. At this time, the high-temperature and high-pressure combustion gas generated in the low combustion chamber 25b expands, so that the fuel density in the high combustion chamber 25a having the second fuel density lower than the first fuel density is increased. The homogeneous mixture is compressed and heated. Thereby, the homogeneous mixture in the high combustion chamber 25a is self-ignited and burned. As a result, the amount of NOx generated with combustion can be reduced as compared with the case where all fuels are burned by the homogeneous spark ignition system.

  In this way, in the self-ignition induced homogeneous spark ignition operation region B, the internal combustion engine 10 is subjected to self-ignition induced homogeneous spark ignition operation.

  As described above, the second embodiment of the internal combustion engine according to the present invention performs the self-ignition-induced homogeneous spark ignition operation in the high load operation region and the extremely high load operation region. As a result, the amount of NOx generated with combustion can be reduced as compared with the case where all fuels are burned by the homogeneous spark ignition system.

(Third embodiment)
Next, an internal combustion engine according to a third embodiment of the present invention will be described. The internal combustion engine according to the third embodiment is arranged so that the fuel injection valve as the fuel injection means and the spark plug as the spark ignition means face the high combustion chamber 25a, and the high load operation region and the extremely high load operation. This is different from the internal combustion engine according to the first embodiment in that self-ignition spontaneous homogeneous spark ignition operation is performed in the region. Hereinafter, this difference will be mainly described.

  As shown in FIG. 17, the internal combustion engine includes an ignition plug 101 as a spark ignition means that replaces the ignition plug 35 and a fuel injection valve 102 as a fuel injection means that replaces the fuel injection valve 37.

  As shown in FIG. 18 when the lower surface of the cylinder head portion 30 is viewed from the combustion chamber 25 side, the spark plug 101 has a cylinder head portion at a position between the two exhaust ports 33 (accordingly, the two exhaust valves 34). 30. The spark plug 101 includes a tip portion that generates sparks (ignition sparks), and the tip portion serves as a combustion chamber 25 (in the period in which the combustion chamber 25 is divided into two spaces, the upper combustion chamber 25a). It has come to be exposed.

  As shown in FIGS. 17 and 18, the fuel injection valve 102 is a side wall surface of the combustion chamber 25 on the cylinder head high portion lower surface 30a side, which is perpendicular to the plane formed by the cylinder head vertical wall surface 30c, and It is disposed at a position on a straight line passing through the central axis of the cylinder 21. The fuel injection valve 102 includes a front end portion that injects fuel toward substantially the center of the combustion chamber 25, and the front end portion is a high portion in the combustion chamber 25 (in the period in which the combustion chamber 25 is divided into two spaces). It is exposed to the combustion chamber 25a). The fuel in the fuel tank (not shown) is supplied to the fuel injection valve 102 by a fuel pressure adjusting means (not shown) and a fuel pump.

  With such a configuration, when fuel is injected from the fuel injection valve 102, if the position of the piston 22 is on the top dead center position side, the injected fuel is caused by the piston upper surface 22a and the cylinder head vertical wall surface 30c. It is blocked and it becomes difficult to reach the space above the lower piston upper surface 22b. In other words, the amount of fuel that reaches the space above the lower piston upper surface 22b increases as the position of the piston 22 at the fuel injection timing (fuel injection timing) is closer to the bottom dead center position.

  As shown in FIG. 19, the internal combustion engine 10 includes a stratified spark ignition operation execution means F31 that constitutes a part of the spark ignition operation execution means, and a self-ignition spontaneous homogeneous spark ignition that constitutes a part of the spark ignition operation execution means. It includes means such as operation execution means F32 and operation switching means G31. The functions of these means are achieved by the CPU of the electric control device 70 executing a predetermined program. Therefore, hereinafter, various operations by the CPU will be described as being performed by the respective means.

  The operation switching means G31 stores the operation region map shown in FIG. 20 in the ROM of the electric control device 70. The operation region map is a map that defines the relationship between the load of the internal combustion engine 10 and the engine rotation speed (rotation speed) NE and the operation method.

  In this operation region map, a stratified spark ignition method and a self-ignition spontaneous homogeneous spark ignition method are designated as operation methods. In this operation region map, the stratified spark ignition operation region A, which is the operation region in which the stratified spark ignition method is designated, is a load region that is smaller than a predetermined high load threshold in the entire operation region. Furthermore, the self-ignition spontaneous homogeneous spark ignition operation region B, which is an operation region in which the self-ignition spontaneous homogeneous spark ignition method is designated, is a region of a load higher than the above-mentioned high load threshold (the higher load side than the stratified spark ignition operation region A). Area).

  The operation switching means G31 determines an operation method based on the operation region map, the load of the internal combustion engine 10 and the engine rotational speed NE, and performs the operation using the determined operation method. The load of the internal combustion engine 10 may be the required torque Tqtgt determined based on the accelerator pedal operation amount Accp and the engine rotational speed NE, or simply the accelerator pedal operation amount Accp.

(When the internal combustion engine 10 is operated in the stratified spark ignition operation region A)
When the internal combustion engine 10 is operated in the stratified spark ignition operation region A (during stratified spark ignition operation), the operation switching means G31 selects the stratified spark ignition operation execution means F31 according to the operation region map. Thereby, the internal combustion engine 10 is operated by the stratified spark ignition operation execution means F31.

  The stratified spark ignition operation execution means F31 performs fuel from the fuel injection valve 102 in the high combustion chamber 25a so that the fuel spatial distribution density (fuel density) is higher in the region near the spark plug 101 than in other regions. Is injected to form a stratified mixture, and the formed stratified mixture is ignited by a spark generated by the spark plug 101 and burned. More specifically, the stratified spark ignition operation execution means F31 operates the intake valve drive mechanism 32a, the exhaust valve drive mechanism 34a, the spark plug 101, and the fuel injection valve 102, respectively, as shown in FIG. The engine 10 is operated.

  The stratified spark ignition operation execution means F31 opens and closes each of the exhaust valve 34 and the intake valve 32 in the same manner as the stratified spark ignition operation execution means F11 included in the internal combustion engine according to the first embodiment ((1 ) To (4).)

  Thereafter, the intake valve 32 is closed by the stratified spark ignition operation execution means F31, and after the intake is completed and the compression of the air is started, the crank angle becomes BTDC 90 ° (the position of the piston 22 is The combustion chamber 25 is divided into two spaces consisting of a high combustion chamber 25a and a low combustion chamber 25b at the timing (which is the combustion chamber division piston position).

  Next, the stratified spark ignition operation execution means F31 opens the fuel injection valve 102, thereby indicating the latter half of the compression stroke at which the crank angle becomes BTDC 45 ° (indicated by the one-dot broken line with A in FIG. 21). The fuel is injected at θinj (see (5)). The amount of fuel injected at this time is based on the load of the internal combustion engine 10 and the engine speed NE so that the air-fuel ratio of the air-fuel mixture in the high combustion chamber 25a becomes a lean air-fuel ratio (lean air-fuel ratio). It is an amount determined.

  At this time, as described above, the combustion chamber 25 is divided into two spaces including a high combustion chamber 25a and a low combustion chamber 25b. Therefore, the injected fuel stays in the vicinity of the cylinder head vertical wall surface 30c as shown in FIG. Thus, more fuel can be collected in the region near the spark plug 101 than in the case where the combustion chamber 25 is not divided into two spaces. As a result, the region where the stratified spark ignition operation can be performed in the light load operation region where the amount of fuel contained in the air-fuel mixture supplied for combustion is small can be expanded, and the fuel efficiency can be improved.

  Thereafter, when the crank angle reaches BTDC 30 °, as shown in FIG. 22B, a stratified mixture is formed in the high combustion chamber 25a in the region near the spark plug 101 in the vicinity of the spark plug 101. Is done.

  Then, the stratified spark ignition operation execution means F31 generates a spark from the tip of the spark plug 101 at the spark ignition timing θig at which the position of the piston 22 is close to the top dead center position, and enters the high combustion chamber 25a. Then, the homogeneous air-fuel mixture is ignited by sparks (by spark ignition) and burned (see (6)). At this time, the stratified spark ignition operation execution means F31 determines the spark ignition timing θig based on the load of the internal combustion engine 10 and the engine speed NE.

  As described above, since the time from the fuel injection timing θinj to the spark ignition timing θig is extremely short, the fuel density of the stratified mixture becomes spatially uniform by the diffusion of the fuel contained in the formed stratified mixture. The stratified mixture can be ignited before becoming As a result, the stratified spark ignition operation can be performed more reliably even in an extremely light load operation region where the amount of fuel contained in the air-fuel mixture provided for combustion is small.

Thereafter, gas expansion accompanying combustion by spark ignition begins.
In this way, in the stratified spark ignition operation region A, the internal combustion engine 10 is stratified spark ignition operated.

(When the internal combustion engine 10 is operated in the self-ignition spontaneous homogeneous spark ignition operation region B)
On the other hand, when the internal combustion engine 10 is operated in the self-ignition spontaneous homogeneous spark ignition operation region B (at the time of self-ignition spontaneous homogeneous spark ignition operation), the operation switching means G31 executes the self-ignition spontaneous homogeneous spark ignition operation according to the operation region map. The means F32 is selected. As a result, the internal combustion engine 10 is operated by the self-ignition spontaneous homogeneous spark ignition operation execution means F32.

  In the self-ignition spontaneous homogeneous spark ignition operation execution means F32, the fuel density in the high combustion chamber 25a becomes the first fuel density that is spatially uniform, and the fuel density in the low combustion chamber 25b is spatially uniform. The fuel is injected from the fuel injection valve 102 so that the second fuel density is lower than the first fuel density, and a homogeneous mixture is formed in each of the high combustion chamber 25a and the low combustion chamber 25b. Further, the self-ignition spontaneous homogeneous spark ignition operation execution means F32 ignites and burns the homogeneous air-fuel mixture formed in the high combustion chamber 25a by the spark generated by the spark plug 101, and the low combustion chamber. The piston 22 compresses the homogeneous air-fuel mixture formed at 25b and causes it to self-ignite and burn.

  The self-ignition spontaneous homogeneous spark ignition operation execution means F32 differs from the stratified spark ignition operation execution means F31 only in that the timing at which fuel is injected is advanced. Therefore, more specific description will be given below centering on such differences.

  The self-ignition spontaneous homogeneous spark ignition operation execution means F32 closes the intake valve 32 to complete the intake and start the compression of the air, and the timing when the crank angle becomes BTDC 100 ° (in FIG. 21). The fuel is injected by opening the fuel injection valve 102 at the timing (θinj) indicated by a one-dot broken line marked with B (see (5)). The amount of fuel injected at this time is such that the air-fuel ratio of the air-fuel mixture in the lower combustion chamber 25b is an extremely lean air-fuel ratio (ultra-lean air-fuel ratio) and the air-fuel ratio of the air-fuel mixture in the higher combustion chamber 25a Is an amount that is determined based on the load of the internal combustion engine 10 and the engine speed NE so as to be the stoichiometric air-fuel ratio.

  At this time, the upper end portion of the piston top vertical wall surface 22c substantially reaches the lower end portion of the cylinder head vertical wall surface 30c. Therefore, most of the injected fuel is blocked by the piston high portion upper surface 22a and the cylinder head vertical wall surface 30c as shown in FIG. Stay. The remaining small amount of fuel reaches the space above the piston lower surface 22b.

  Thereafter, as shown in FIG. 23B, at the timing when the crank angle becomes BTDC 90 ° (the position of the piston 22 becomes the combustion chamber split piston position), the combustion chamber 25 is separated from the high combustion chamber 25a and the low combustion chamber 25a. It is divided into two spaces consisting of partial combustion chambers 25b. As a result, in the high combustion chamber 25a, a homogeneous mixture (homogeneous mixture whose air-fuel ratio is the stoichiometric air-fuel ratio) that is the first fuel density in which the fuel density is spatially uniform is formed, and low In the partial combustion chamber 25b, a homogeneous mixture (homogeneous mixture in which the air-fuel ratio is an ultra lean air-fuel ratio) having a second fuel density lower than the first fuel density in which the fuel density is spatially uniform is formed. Is done.

  Then, the self-ignition spontaneous homogeneous spark ignition operation execution means F32 generates a spark from the tip of the spark plug 101 at the spark ignition timing θig immediately before the piston 22 reaches the top dead center position, and the inside of the high combustion chamber 25a The homogeneous mixture is ignited by sparks (by spark ignition) and burned (see (6)). At this time, the self-ignition spontaneous homogeneous spark ignition operation execution means F32 determines the spark ignition timing θig based on the load of the internal combustion engine 10 and the engine speed NE.

  Thereafter, when the piston 22 approaches the top dead center position, the air-fuel mixture is self-ignited in the lower combustion chamber 25b. Thus, the temperature of the air-fuel mixture in the lower combustion chamber 25b that is compressed to a greater degree is the combustion gas generated in the higher combustion chamber 25a by the communication between the higher combustion chamber 25a and the lower combustion chamber 25b. Even if the air-fuel mixture is not compressed and heated by the pressure, the piston 22 compresses the air-fuel mixture and the temperature becomes sufficiently high. Accordingly, the air-fuel mixture is self-ignited in the lower combustion chamber 25b during the period in which the combustion chamber 25 is divided.

  Thereby, compared with the case where all the fuels are burned by the homogeneous spark ignition method, the amount of NOx produced with combustion can be reduced. Furthermore, the timing at which the air-fuel mixture in the lower combustion chamber 25b is self-ignited and the timing at which the air-fuel mixture in the high combustion chamber 25a is ignited by sparks are expressed as follows: Can be close to each other (when the piston 22 is at the top dead center position side of the combustion chamber division piston position) before the communication is established. As a result, the equal volume can be improved, and the fuel efficiency can be improved.

  In this way, in the self-ignition spontaneous homogeneous spark ignition operation region B, the internal combustion engine 10 is subjected to self-ignition spontaneous homogeneous spark ignition operation.

  As described above, the third embodiment of the internal combustion engine according to the present invention includes the ignition plug 101 and the fuel injection valve 102 disposed so as to face the high combustion chamber 25a, as well as the high load operation region and the extreme height. Self-ignition spontaneous homogeneous spark ignition operation is performed in the load operation area.

  As a result, the amount of NOx generated with combustion can be reduced as compared with the case where all fuels are burned by the homogeneous spark ignition system. Furthermore, since the ignition timings in the high combustion chamber 25a and the low combustion chamber 25b can be close to each other, the equal volume can be improved and the fuel consumption can be improved.

(Fourth embodiment)
Next, an internal combustion engine according to a fourth embodiment of the present invention will be described. The internal combustion engine according to the fourth embodiment includes, as spark ignition means, a first ignition plug disposed so as to face the low combustion chamber 25b and a second ignition disposed so as to face the high combustion chamber 25a. The internal combustion engine according to the first embodiment is different from the first embodiment in that the two spark plugs including the plug are provided and the two-chamber homogeneous spark ignition operation is performed in the extremely high load operation region. Hereinafter, this difference will be mainly described.

  As shown in FIG. 24, the internal combustion engine includes a first spark plug 111 as a first spark ignition means instead of the spark plug 35, and a second spark plug 112 as a second spark ignition means. .

  The first spark plug 111 has a cylinder at a position between the two intake ports 31 (and thus the two intake valves 32) as shown in FIG. 25 when the lower surface of the cylinder head portion 30 is viewed from the combustion chamber 25 side. The head unit 30 is disposed. The first spark plug 111 includes a tip portion that generates a spark (ignition spark), and the tip portion is in the combustion chamber 25 (in the period in which the combustion chamber 25 is divided into two spaces, the lower combustion chamber 25b). ) Is exposed.

  The second spark plug 112 is disposed in the cylinder head portion 30 at a position between the two exhaust ports 33 (therefore, the two exhaust valves 34). The second spark plug 112 includes a tip portion that generates a spark (ignition spark), and the tip portion is in the combustion chamber 25 (in the period in which the combustion chamber 25 is divided into two spaces, the high combustion chamber 25a). ) Is exposed.

  As shown in FIG. 26, the internal combustion engine 10 constitutes a part of a stratified spark ignition operation execution means F41, a self-ignition operation execution means F42, and a part of the spark ignition operation execution means that constitute a part of the spark ignition operation execution means. The two-chamber homogeneous spark ignition operation execution means F43 and the operation switching means G41 are included. The functions of these means are achieved by the CPU of the electric control device 70 executing a predetermined program. Therefore, hereinafter, various operations by the CPU will be described as being performed by the respective means.

  The operation switching means G41 stores the operation region map shown in FIG. 27 in the ROM of the electric control device 70. The operation region map is a map that defines the relationship between the load of the internal combustion engine 10 and the engine rotation speed (rotation speed) NE and the operation method.

  In this operation region map, a stratified spark ignition method, a premixed compression auto-ignition method, and a two-chamber homogeneous spark ignition method are designated as operation methods. In this operation region map, the stratified spark ignition operation region A, which is the operation region in which the stratified spark ignition method is designated, is a load region that is smaller than a predetermined high load threshold in the entire operation region.

  Furthermore, the self-ignition operation region B, which is an operation region in which the premixed compression self-ignition method is designated, is a region of a load that is equal to or higher than the high load threshold (a region on the higher load side than the stratified spark ignition operation region A). Thus, the load region is smaller than a predetermined extremely high load threshold value that is larger than the high load threshold value. In addition, the two-chamber homogeneous spark ignition operation region C, which is an operation region in which the two-chamber homogeneous spark ignition system is designated, is a load region that is equal to or higher than the above-mentioned extremely high load threshold (on the higher load side than the self-ignition operation region B). Area).

  The operation switching means G41 determines an operation method based on the operation region map, the load of the internal combustion engine 10 and the engine rotational speed NE, and performs operation according to the determined operation method. The load of the internal combustion engine 10 may be the required torque Tqtgt determined based on the accelerator pedal operation amount Accp and the engine rotational speed NE, or simply the accelerator pedal operation amount Accp.

(When the internal combustion engine 10 is operated in the stratified spark ignition operation region A)
When the internal combustion engine 10 is operated in the stratified spark ignition operation region A (during stratified spark ignition operation), the operation switching means G41 selects the stratified spark ignition operation execution means F41 according to the operation region map. Thereby, the internal combustion engine 10 is operated by the stratified spark ignition operation execution means F41.

  The stratified spark ignition operation execution means F41 is the same as the stratified spark ignition operation execution means F11 included in the internal combustion engine according to the first embodiment. Therefore, the stratified spark ignition operation execution means F41 operates the intake valve drive mechanism 32a, the exhaust valve drive mechanism 34a, the first spark plug 111 instead of the spark plug 35, and the fuel injection valve 37, respectively, as shown in FIG. The internal combustion engine 10 is operated. Thereby, in the stratified spark ignition operation region A, the internal combustion engine 10 is stratified spark ignition operated.

(When the internal combustion engine 10 is operated in the self-ignition operation region B)
Further, when the internal combustion engine 10 is operated in the self-ignition operation region B (at the time of self-ignition operation), the operation switching means G41 selects the self-ignition operation execution means F42 according to the operation region map. Thereby, the internal combustion engine 10 is operated by the self-ignition operation executing means F42.

  The self-ignition operation executing means F42 is the same as the self-ignition operation executing means F12 included in the internal combustion engine according to the first embodiment. Therefore, the self-ignition operation execution means F42 operates the internal combustion engine 10 by operating the intake valve drive mechanism 32a, the exhaust valve drive mechanism 34a, and the fuel injection valve 37, respectively, as shown in FIG. Thereby, in the self-ignition operation region B, the internal combustion engine 10 is self-ignited.

(When the internal combustion engine 10 is operated in the two-chamber homogeneous spark ignition operation region C)
On the other hand, when the internal combustion engine 10 is operated in the two-chamber homogeneous spark ignition operation region C (during the two-chamber homogeneous spark ignition operation), the operation switching means G41 causes the two-chamber homogeneous spark ignition operation executing means F43 to follow the operation region map. select. Thereby, the internal combustion engine 10 is operated by the two-chamber homogeneous spark ignition operation execution means F43.

  The both-chamber homogeneous spark ignition operation execution means F43 is a fuel injection valve so that the fuel density in the high combustion chamber 25a is spatially uniform and the fuel density in the low combustion chamber 25b is spatially uniform. The fuel is injected from 37, and a homogeneous mixture is formed in each of the high combustion chamber 25a and the low combustion chamber 25b. Furthermore, the both-chamber homogeneous spark ignition operation execution means F43 ignites and burns the homogeneous air-fuel mixture formed in the upper combustion chamber 25a with the spark generated by the second spark plug 112 at the first spark ignition timing. In addition, the homogeneous air-fuel mixture formed in the lower combustion chamber 25b is ignited by the spark generated by the first spark plug 111 at the second spark ignition timing that is retarded from the first spark ignition timing. Burn.

  More specifically, as shown in FIG. 28, the two-chamber homogeneous spark ignition operation execution means F43 includes an intake valve drive mechanism 32a, an exhaust valve drive mechanism 34a, a first spark plug 111, a second spark plug 112, and The internal combustion engine 10 is operated by operating each of the fuel injection valves 37.

  First, the two-chamber homogeneous spark ignition operation execution means F43 drives the exhaust valve drive mechanism 34a to open the exhaust valve 34 at the spark ignition exhaust valve opening timing EO corresponding to the load of the internal combustion engine 10. (See (1).) Thereby, exhaust of the combustion gas produced | generated by the combustion in the last combustion cycle starts. Next, the two-chamber homogeneous spark ignition operation execution means F43 drives the exhaust valve drive mechanism 34a to close the exhaust valve 34 at the spark ignition exhaust valve closing timing EC corresponding to the load of the internal combustion engine 10. (See (2).) Thereby, exhaust ends.

  Thereafter, the two-chamber homogeneous spark ignition operation execution means F43 drives the intake valve drive mechanism 32a to open the intake valve 32 at the spark ignition intake valve opening timing IO corresponding to the load of the internal combustion engine 10. (See (3).) Thereby, inhalation is started.

  Then, the both-chamber homogeneous spark ignition operation execution means F43 opens the fuel injection valve 37 so that the intake stroke from the spark ignition intake valve opening timing IO to the spark ignition intake valve closing timing IC, which will be described later, is changed. The fuel is injected at the initial and / or intermediate timing θinj (see (4)). The amount of fuel injected at this time is an amount determined based on the load of the internal combustion engine 10 and the engine speed NE so that the air-fuel ratio of the air-fuel mixture in the combustion chamber 25 is the stoichiometric air-fuel ratio. The injected fuel is uniformly (uniformly) distributed in the combustion chamber 25 by the flow of air subsequently sucked into the combustion chamber 25.

  Next, the two-chamber homogeneous spark ignition operation execution means F43 drives the intake valve drive mechanism 32a to close the intake valve 32 at the spark ignition intake valve closing timing IC corresponding to the load of the internal combustion engine 10. (Refer to (5).) The spark ignition intake valve closing timing IC is retarded from the self-ignition intake valve closing timing IC (see FIG. 9) in order to avoid knocking that tends to occur when the air-fuel mixture is greatly compressed. Set to be on the side. As a result, the intake air is finished and the compression of the air-fuel mixture including fuel and air is started.

  Thereafter, at the timing when the crank angle becomes BTDC 90 ° (the position of the piston 22 becomes the combustion chamber division piston position), the combustion chamber 25 is divided into two spaces consisting of a high combustion chamber 25a and a low combustion chamber 25b. The As a result, in the high combustion chamber 25a and the low combustion chamber 25b, the air-fuel mixture having a spatially uniform fuel density and substantially the same fuel density (the air-fuel ratio is the stoichiometric air-fuel ratio) respectively. It is formed.

  Then, the two-chamber homogeneous spark ignition operation execution means F43 generates a spark from the tip of the second spark plug 112 at the first spark ignition timing θig1 at which the position of the piston 22 is in the vicinity of the top dead center position. Then, the air-fuel mixture is ignited by sparks (by spark ignition) and burned in the upper combustion chamber 25a (see (6)). Further, the both-chamber homogeneous spark ignition operation execution means F43 generates a spark from the tip of the first spark plug 111 at the second spark ignition timing θig2 that is retarded (later) than the first spark ignition timing θig1. Then, the air-fuel mixture is ignited by a spark in the lower combustion chamber 25b and burned (see (7)). At this time, the two-chamber homogeneous spark ignition operation execution means F43 determines the first spark ignition timing θig1 and the second spark ignition timing θig2 based on the load of the internal combustion engine 10 and the engine speed NE.

  Next, when the piston 22 is extremely close to the top dead center position, substantially simultaneously, the generated heat energy in the high combustion chamber 25a and the generated heat energy in the low combustion chamber 25b are respectively the maximum generated heat energy in each space. Become. Thus, compared with the case where the spark ignition timings in the two spaces of the high combustion chamber 25a and the low combustion chamber 25b are equal to each other, the maximum thermal energy timings in the two spaces are close to each other. . As a result, the thermal efficiency can be improved and the maximum output of the internal combustion engine can be improved.

Thereafter, gas expansion accompanying combustion by spark ignition begins.
In this way, in the two-chamber homogeneous spark ignition operation region C, the internal combustion engine 10 is subjected to the two-chamber homogeneous spark ignition operation. As a result, it is possible to prevent the generation of excessive noise compared to the case where the self-ignition operation is performed.

  As described above, the fourth embodiment of the internal combustion engine according to the present invention faces the first ignition plug 111 disposed so as to face the lower combustion chamber 25b and the higher combustion chamber 25a as spark ignition means. The two spark plugs comprising the second spark plug 112 arranged as described above are provided, and the two-chamber homogeneous spark ignition operation is performed in the extremely high load operation region.

  Thereby, the maximum thermal energy timing in each of the two spaces can be made close to each other. As a result, the thermal efficiency can be improved and the maximum output of the internal combustion engine can be improved.

  As described above, in each embodiment of the internal combustion engine according to the present invention, when the piston 22 is on the top dead center position side with respect to the combustion chamber division piston position, the high combustion chamber 25a and the low combustion chamber 25 are separated from each other. It is configured to be divided into two spaces consisting of partial combustion chambers 25b. Thereby, in the period when the combustion chamber 25 is divided, the region in which the fuel in each space can diffuse becomes narrower than in the case where the combustion chamber is not divided into two spaces. As a result, more fuel can be collected in the region near the spark plug. As a result, the region where the stratified spark ignition operation can be performed in the light load operation region where the amount of fuel contained in the air-fuel mixture supplied for combustion is small can be expanded, and the fuel efficiency can be improved.

  In addition, this invention is not limited to said each embodiment, A various modification can be employ | adopted within the scope of the present invention. For example, although each said embodiment was comprised so that a fuel might be injected only once, you may be comprised so that it may inject two or more times.

  Furthermore, although the piston top vertical wall surface 22c and the cylinder head vertical wall surface 30c in the above embodiments are flat surfaces, they may be curved surfaces. Further, although the supercharger 91 in each of the above embodiments is a turbocharger, it may be a mechanical supercharger (supercharger). Further, during the self-ignition operation, more stable combustion may be ensured by generating an ignition spark as an auxiliary.

1 is a schematic view of an internal combustion engine according to a first embodiment of the present invention. FIG. 2 is a partially enlarged sectional view in the vicinity of a combustion chamber of the internal combustion engine shown in FIG. 1. It is the figure which showed typically the change of the combustion chamber shown in FIG. 1 with respect to the crank angle. It is the schematic which looked at the lower surface of the cylinder head part shown in FIG. 1 from the combustion chamber side. FIG. 2 is a functional block diagram showing a program executed by a CPU of the electric control device shown in FIG. 1. It is the figure which showed the driving | operation area | region map which CPU of the electric control apparatus shown in FIG. 1 refers. FIG. 2 is an explanatory diagram conceptually showing opening / closing timings, fuel injection timings, and spark ignition timings of an intake valve and an exhaust valve of a cylinder when the internal combustion engine shown in FIG. 1 is operated by a spark ignition system. It is explanatory drawing which showed notionally the spatial distribution of the fuel injected at the fuel-injection timing shown in FIG. FIG. 2 is an explanatory diagram conceptually showing opening / closing timings and fuel injection timings of an intake valve and an exhaust valve of a cylinder when the internal combustion engine shown in FIG. 1 is operated by a premixed compression auto-ignition system. It is explanatory drawing which showed notionally the spatial distribution of the fuel injected at the fuel-injection timing shown in FIG. It is the graph which showed the heat energy generated in a combustion chamber to the crank angle. It is explanatory drawing which showed notionally the spatial distribution of the fuel injected at the fuel-injection timing shown in FIG. It is the functional block diagram which showed the program which CPU of the internal combustion engine which concerns on 2nd Embodiment of this invention runs. It is the figure which showed the driving | operation area | region map which CPU of the internal combustion engine which concerns on 2nd Embodiment of this invention refers. FIG. 6 is an explanatory diagram conceptually showing opening / closing timings, fuel injection timings, and spark ignition timings of an intake valve and an exhaust valve of a cylinder when an internal combustion engine according to a second embodiment of the present invention is operated by a spark ignition method. is there. It is explanatory drawing which showed notionally the spatial distribution of the fuel injected at the fuel injection timing shown in FIG. It is the figure which showed typically the fuel-injection means with which the internal combustion engine which concerns on 3rd Embodiment of this invention is provided, and a spark ignition means. It is the schematic which looked at the lower surface of the cylinder head part shown in FIG. 17 from the combustion chamber side. It is the functional block diagram which showed the program which CPU of the internal combustion engine which concerns on 3rd Embodiment of this invention runs. It is the figure which showed the driving | operation area | region map which CPU of the internal combustion engine which concerns on 3rd Embodiment of this invention refers. It is explanatory drawing which showed notionally the opening / closing timing of the intake valve and exhaust valve of a certain cylinder, fuel injection timing, and spark ignition timing in case the internal combustion engine which concerns on 3rd Embodiment of this invention is drive | operated by a spark ignition system. is there. It is explanatory drawing which showed notionally the spatial distribution of the fuel injected at the fuel-injection timing shown in FIG. It is explanatory drawing which showed notionally the spatial distribution of the fuel injected at the fuel-injection timing shown in FIG. It is the figure which showed typically the spark ignition means with which the internal combustion engine which concerns on 4th Embodiment of this invention is provided. It is the schematic which looked at the lower surface of the cylinder head part shown in FIG. 24 from the combustion chamber side. It is the functional block diagram which showed the program which CPU of the internal combustion engine which concerns on 4th Embodiment of this invention runs. It is the figure which showed the driving | operation area | region map which CPU of the internal combustion engine which concerns on 4th Embodiment of this invention refers. It is explanatory drawing which showed notionally the opening / closing timing of the intake valve and exhaust valve of a certain cylinder, fuel injection timing, and spark ignition timing in case the internal combustion engine which concerns on 4th Embodiment of this invention is drive | operated by a spark ignition system. is there.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 20 ... Cylinder block part, 21 ... Cylinder, 22 ... Piston, 22a ... Piston high part upper surface, 22a1 ... Piston high part ring, 22b ... Piston low part upper surface, 22c ... Piston top vertical wall surface, 22d ... Piston ring, 23 ... Connecting rod, 24 ... Crankshaft, 25 ... Combustion chamber, 25a ... High combustion chamber, 25b ... Low combustion chamber, 30 ... Cylinder head, 30a ... Cylinder head high bottom, 30b ... Cylinder head low Lower part surface, 30c ... Vertical wall surface of cylinder head, 31 ... Intake port, 32 ... Intake valve, 32a ... Intake valve drive mechanism, 33 ... Exhaust port, 34 ... Exhaust valve, 34a ... Exhaust valve drive mechanism, 35 ... Spark plug, 36 Igniter 37 fuel injection valve 38 drive circuit 61 crank position sensor 62 accelerator position sensor 70 electric Controller, 101 ... ignition plug, 102 ... fuel injection valve, 111 ... first spark plug, 112 ... second spark plug.

Claims (8)

A cylinder block in which a cylinder bore is formed; a cylinder head disposed at an upper portion of the cylinder block; a piston that reciprocates in the cylinder bore; at least a wall surface of the cylinder bore; a lower surface of the cylinder head; and a top surface of the piston. A fuel injection means for injecting fuel into the combustion chamber, a spark ignition means for generating a spark in the combustion chamber, an air introduced into the combustion chamber, and the fuel injection means for injection A spark ignition operation executing means for performing an operation by a spark ignition method in which an air-fuel mixture containing the formed fuel is formed in the combustion chamber and the air-fuel mixture thus formed is ignited by the spark generated by the spark ignition means and burned. In an internal combustion engine comprising:
The combustion chamber is divided into two spaces consisting of a first space and a second space that are independent from each other when the piston is on the top dead center position side from a predetermined position, and the piston is at the top dead center position. The first space volume ratio, which is the ratio of the volume of the first space when the piston is at the predetermined position to the volume of the first space, is the second space when the piston is at the top dead center position. Is configured to be larger than a second space volume ratio, which is a ratio of the volume of the second space when the piston is in the predetermined position with respect to the volume of
The fuel injection means is arranged to face the first space,
The spark ignition means is arranged to face the first space,
The spark ignition operation execution means is configured to cause the fuel density, which is a spatial distribution density of fuel contained in the air-fuel mixture in the first space, to be higher in the area near the spark ignition means than in other areas. A stratified spark ignition operation is performed in which the fuel is injected by the injection means to form a stratified mixture, and the stratified mixture is ignited by a spark generated by the spark ignition means and burned. Internal combustion engine including means. The internal combustion engine according to claim 1,
The stratified spark ignition operation execution means is an internal combustion engine that injects the fuel by the fuel injection means in the latter half of the compression stroke. The internal combustion engine according to claim 1 or 2,
By introducing air into the combustion chamber, forming an air-fuel mixture containing the introduced air, fuel injected by the fuel injection means, and combustion gas in the combustion chamber, and compressing the formed air-fuel mixture A self-ignition operation executing means for performing an operation by a premixed compression auto-ignition method in which self-ignition is performed in the first space and the second space to burn;
When the load of the internal combustion engine is a high load equal to or higher than a predetermined high load threshold, the self-ignition operation execution means is operated to operate the internal combustion engine, and the load of the internal combustion engine is a light load smaller than the high load threshold. When there is, operation switching means for operating the internal combustion engine by the stratified spark ignition operation execution means of the spark ignition operation execution means,
An internal combustion engine. The internal combustion engine according to claim 3,
The spark ignition operation execution means forms the homogeneous mixture by injecting the fuel by the fuel injection means in the first half of the compression stroke so that the fuel density in the first space is spatially uniform. A homogeneous spark ignition operation executing means for performing an operation by a homogeneous spark ignition system for igniting and burning the homogeneous air-fuel mixture generated by the spark generated by the spark ignition means,
When the load of the internal combustion engine is an extremely high load equal to or greater than a predetermined extremely high load threshold greater than the high load threshold, the operation switching means is operated by the homogeneous spark ignition operation executing means of the spark ignition operation executing means. The internal combustion engine that makes the operation of. The internal combustion engine according to claim 1 or 2,
The spark ignition operation execution means has the first fuel density in which the fuel density in the first space is spatially uniform and the fuel density in the second space is spatially uniform. The fuel is injected by the fuel injection means so as to have a second fuel density lower than the density to form a homogeneous mixture in each of the first space and the second space, and formed in the first space. The generated homogeneous mixture is ignited by the spark generated by the spark ignition means and burned, and the homogeneous mixture formed in the second space is compressed by the combustion gas generated by the combustion in the first space. Including self-ignition-induced homogeneous spark ignition operation execution means for performing operation by a self-ignition-induced homogeneous spark ignition method for self-ignition and burning by
When the load of the internal combustion engine is a high load equal to or higher than a predetermined high load threshold, the internal combustion engine is operated by the self-ignition induced homogeneous spark ignition operation execution means of the spark ignition operation execution means, and the load of the internal combustion engine An internal combustion engine comprising operation switching means for causing the internal combustion engine to be operated by the stratified spark ignition operation executing means of the spark ignition operation executing means when is a light load smaller than the high load threshold. A cylinder block in which a cylinder bore is formed; a cylinder head disposed at an upper portion of the cylinder block; a piston that reciprocates in the cylinder bore; at least a wall surface of the cylinder bore; a lower surface of the cylinder head; and a top surface of the piston. A fuel injection means for injecting fuel into the combustion chamber, a spark ignition means for generating a spark in the combustion chamber, an air introduced into the combustion chamber, and the fuel injection means for injection An internal combustion engine comprising: a spark ignition operation executing means for performing an operation by a spark ignition method in which an air-fuel mixture containing the formed fuel is formed and the air-fuel mixture thus formed is ignited by the spark generated by the spark ignition means and burned In
The combustion chamber is divided into two spaces consisting of a first space and a second space that are independent from each other when the piston is on the top dead center position side from a predetermined position, and the piston is at the top dead center position. The first space volume ratio, which is the ratio of the volume of the first space when the piston is at the predetermined position to the volume of the first space, is the second space when the piston is at the top dead center position. Is configured to be larger than a second space volume ratio, which is a ratio of the volume of the second space when the piston is in the predetermined position with respect to the volume of
The fuel injection means is arranged to face the second space,
The spark ignition means is arranged to face the second space,
The spark ignition operation execution means has a first uniform fuel density in which the fuel density, which is a spatial distribution density of fuel contained in the air-fuel mixture in the second space, is spatially uniform, and in the first space. The fuel is injected by the fuel injection means so that the fuel density becomes a second fuel density lower than the first fuel density, which is spatially uniform, in each of the first space and the second space. A homogeneous mixture is formed, and the homogeneous mixture formed in the second space is ignited by the spark generated by the spark ignition means and burned, and the homogeneous mixture formed in the first space is An internal combustion engine configured to self-ignite and burn when compressed by a piston. A cylinder block in which a cylinder bore is formed; a cylinder head disposed at an upper portion of the cylinder block; a piston that reciprocates in the cylinder bore; at least a wall surface of the cylinder bore; a lower surface of the cylinder head; and a top surface of the piston. A fuel injection means for injecting fuel into the combustion chamber, a spark ignition means for generating a spark in the combustion chamber, an air introduced into the combustion chamber, and the fuel injection means for injection An internal combustion engine comprising: a spark ignition operation executing unit configured to perform an operation by a spark ignition method in which an air-fuel mixture including the generated fuel is formed and the air-fuel mixture formed by the spark ignition unit is ignited by a spark generated by the spark ignition unit and burned. In
The combustion chamber is divided into two spaces consisting of a first space and a second space that are independent from each other when the piston is on the top dead center position side from a predetermined position, and the piston is at the top dead center position. The first space volume ratio, which is the ratio of the volume of the first space when the piston is at the predetermined position to the volume of the first space, is the second space when the piston is at the top dead center position. Is configured to be larger than a second space volume ratio, which is a ratio of the volume of the second space when the piston is in the predetermined position with respect to the volume of
The spark ignition means includes a first spark ignition means arranged to face the first space, and a second spark ignition means arranged to face the second space,
The spark ignition operation execution means causes the fuel injection means to distribute the fuel so that the fuel density in the second space is spatially uniform and the fuel density in the first space is spatially uniform. The second spark ignition means is injected to form a homogeneous mixture in each of the first space and the second space, and the homogeneous mixture formed in the second space is at a first spark ignition timing. Is ignited and burned by the sparks generated, and the first spark ignition is performed at the second spark ignition timing retarded from the first spark ignition timing with respect to the homogeneous mixture formed in the first space. An internal combustion engine configured to be ignited and burned by a spark generated by the means. The internal combustion engine according to claim 7,
By introducing air into the combustion chamber, forming an air-fuel mixture containing the introduced air, fuel injected by the fuel injection means, and combustion gas in the combustion chamber, and compressing the formed air-fuel mixture A self-ignition operation executing means for performing an operation by a premixed compression auto-ignition method in which self-ignition is performed in the first space and the second space to burn;
When the load of the internal combustion engine is smaller than a predetermined load threshold, the self-ignition operation execution means is operated to perform the operation of the internal combustion engine, and the load of the internal combustion engine is a load equal to or higher than the predetermined load threshold Operation switching means for operating the internal combustion engine by the spark ignition operation execution means;
An internal combustion engine.

Images