JP2006257999A - Internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an internal combustion engine reducing noise in self-ignition operation in a high load operational area. <P>SOLUTION: In this internal combustion engine, when a piston 22 is closer to a top dead center position side than a predetermined position, a combustion chamber 25 is split into two spaces of a high combustion chamber 25a and a low combustion chamber 25b which are independent from each other, a ratio VH0/VH1 of a high combustion chamber volume when the piston is at a top dead center position with respect to that when the piston is at the predetermined position is set to be larger than a ratio VL0/VL1 of a low combustion chamber volume when the piston is at a top dead center position with respect to that when the piston is at the predetermined position. Therefore, self-ignition of fuel mixture in the high combustion chamber is performed, and then self-ignition of mixture gas in a low combustion chamber is performed after a lapse of a predetermined time. The noise along with combustion can be reduced in this invention, compared with a case where self-ignition of fuel mixture in the combustion chamber 25 is performed all together. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an internal combustion engine that operates in a premixed compression self-ignition system in which a mixed gas containing air and fuel is formed in a combustion chamber, and the mixed gas is compressed in the combustion chamber so as to self-ignite and burn. About.

Conventionally, a mixed gas containing air and fuel is formed in a combustion chamber, and the mixed gas is compressed in the combustion chamber so that it is self-ignited and burned for operation (self-ignition operation). There is known an internal combustion engine that performs (see, for example, Patent Document 1).
JP 2002-227680 A

  This conventional internal combustion engine is operated with a very lean air-fuel ratio (ultra-lean air-fuel ratio) of the mixed gas in the combustion chamber and a high compression ratio. As a result, fuel consumption can be improved and the amount of NOx produced with combustion can be reduced.

  By the way, in the combustion chamber of the internal combustion engine performing the self-ignition operation, the compressed mixed gas is ignited almost simultaneously at a number of scattered positions and burns within a very short period. Therefore, when self-ignition operation is performed particularly in a high load operation region where the amount of fuel is large, extremely large heat energy is generated within an extremely short period.

  For this reason, in the high load operation region, the impact force per unit time caused by the thermal energy generated by the combustion of the piston, cylinder block and cylinder head constituting the combustion chamber becomes excessive. Since the generated noise becomes excessive, there is a problem that self-ignition operation cannot be performed.

  The present invention has been made in order to address the above-described problems, and one of its purposes is to provide an internal combustion engine that can reduce noise during self-ignition operation in a high-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. And a fuel injection means for injecting fuel supplied into a combustion chamber constituted by a lower surface of the cylinder head and a top surface of the piston, and an intake port formed in the cylinder head for supplying air into the combustion chamber And an exhaust valve that opens and closes an exhaust port that is formed in the cylinder head and discharges combustion gas in the combustion chamber from the combustion chamber.

  The internal combustion engine according to the present invention is operated by a premixed compression self-ignition method in which a mixed gas containing air, fuel, and combustion gas is formed in the combustion chamber and the mixture gas is compressed to self-ignite and burn.

  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.

  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. 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 mixed gas in the first space is compressed more than the mixed gas in the second space. As a result, the temperature of the mixed gas in the first space is higher than the temperature of the mixed gas in the second space. For this reason, the mixed gas in the first space is self-ignited and burned before the mixed gas in the second space. That is, the mixed gas is self-ignited and burned at different timings in the two spaces.

  Thereby, the magnitude of the impact force per unit time caused by the thermal energy generated by the combustion of the piston, cylinder block, cylinder head and other members constituting the combustion chamber is such that the mixed gas in the combustion chamber is temporarily (very short). Since it is smaller than the case of self-ignition and combustion within a period of time, the noise generated with the impact is reduced. As a result, since the operation (self-ignition operation) by the premixed compression self-ignition method can be performed in a higher load operation region, the fuel consumption can be improved and the amount of NOx generated with combustion can be reduced. Can be reduced.

In this case, the piston is formed such that the top surface of the piston has a piston top vertical wall surface that is a surface orthogonal to a plane orthogonal to the central axis of the cylinder bore,
The cylinder head is formed such that a lower surface of the cylinder head has a cylinder head vertical wall surface that is a surface orthogonal to a plane orthogonal to the central axis of the cylinder bore, and
The combustion chamber is divided into the two spaces by the piston top vertical wall surface and the cylinder head vertical wall surface facing each other when the piston is closer to the top dead center position than the predetermined position. It is suitable to be configured.

  According to this, the combustion chamber divided into two spaces when the piston is at the top dead center position side from the predetermined position can be easily configured.

In this case, the exhaust valve is arranged to face the first space,
The intake valve is preferably arranged so as to face the second space.

  In general, in an internal combustion engine that performs self-ignition operation, combustion gas is used in order to make the mixed gas easier to be self-ignited by increasing the temperature of the mixed gas (to improve the ignitability of the mixed gas). . In order to include the combustion gas in the mixed gas, a part of the combustion gas generated by the combustion in the previous combustion cycle remains in the combustion chamber, or the combustion gas exhausted from the combustion chamber enters the combustion chamber again from the exhaust port. It is often introduced or done. As a result, of the mixed gas formed in the combustion chamber, the mixed gas in the vicinity of the exhaust valve contains more combustion gas than the mixed gas in the vicinity of the intake valve.

  Therefore, as described above, the exhaust valve is arranged so as to face the first space, and the intake valve is arranged so as to face the second space, so that the mixed gas formed in the first space can be prevented. The ratio of the combustion gas contained in the mixed gas is higher than the ratio of the combustion gas contained in the mixed gas with respect to the mixed gas formed in the second space.

  For this reason, the temperature of the mixed gas formed in the first space can be made higher than the temperature of the mixed gas formed in the second space. As a result, the difference between the ignitability of the mixed gas in the first space and the ignitability of the mixed gas in the second space can be further increased. Accordingly, even if the difference between the first space volume ratio and the second space volume ratio cannot be increased in order to maintain the balance of the pistons, the timing at which each of the mixed gases in the two spaces is self-ignited is increased. Can be different.

In this case, when the load of the internal combustion engine is a light load smaller than a predetermined light load threshold, out of the amount of fuel determined according to the load required for the internal combustion engine, accompanying the compression due to the movement of the piston The fuel injection means injects the fuel so that the amount of fuel necessary for self-ignition and combustion of the mixed gas formed in the first space is included in the mixed gas,
When the load of the internal combustion engine is a medium-high load that is equal to or higher than the light load threshold, it is necessary for the mixed gas formed in each of the two spaces to be self-ignited and combusted with the compression caused by the movement of the piston. It is preferable that fuel injection control means for injecting fuel by the fuel injection means is provided so that an amount of fuel is included in each mixed gas.

  In the light load operation region, the amount of fuel required by the internal combustion engine is reduced, so the spatial distribution density of fuel in the combustion chamber is reduced. For this reason, in the light load operation region, the mixed gas in the combustion chamber may not be self-ignited, and the combustion cycle may end (misfire).

  By the way, as described above, the temperature of the mixed gas in the first space becomes higher than the temperature of the mixed gas in the second space with the compression due to the movement of the piston. That is, the ignitability of the mixed gas in the first space is better than the ignitability of the mixed gas in the second space.

  Accordingly, in the light load operation region as described above, the same amount of fuel is contained in the mixed gas in the first space where the temperature becomes higher, so that the mixed gas is self-ignited. The ignitability of the mixed gas in the first space can be further improved. As a result, the mixed gas in the first space can be surely self-ignited.

  In this case, when the load of the internal combustion engine is a medium load that is smaller than a predetermined high load threshold that is greater than the light load threshold and greater than or equal to the light load threshold, the fuel injection control means When the spatial fuel ratio, which is the ratio of the amount of fuel contained in the mixed gas in the second space to the amount of fuel contained in the mixed gas, is a high load equal to or higher than the high load threshold It is preferable that the fuel is injected by the fuel injection means so as to be larger than the same fuel ratio.

  In a medium-load operation region where there is little risk of excessive noise generation, when the piston is in the vicinity of the top dead center position, if the mixed gas is self-ignited and burned substantially simultaneously in the two spaces, the isovolume is increased. As a result, fuel efficiency is improved.

  Therefore, as in the above configuration, in the medium load operation region, the spatial fuel ratio, which is the ratio of the amount of fuel contained in the mixed gas in the second space to the amount of fuel contained in the mixed gas in the first space, is The fuel is injected by the fuel injection means so as to be larger than the space fuel ratio in the high load operation region.

  Thereby, in the medium load operation region where the possibility of excessive noise is small, the timing at which the mixed gas in the first space is self-ignited and the timing at which the mixed gas in the second space is self-ignited The ignition timing interval is smaller than the ignition timing interval in the high load operation region. As a result, the equal volume can be increased, and the fuel efficiency can be improved.

In this case, when the rotational speed of the internal combustion engine is a high rotational speed that is equal to or higher than a predetermined high rotational speed threshold, the amount of fuel determined by the load required for the internal combustion engine depends on the movement of the piston. The fuel injection means injects the fuel so that the amount of fuel necessary for self-ignition and combustion of the mixed gas formed in the first space with compression is included in the mixed gas, on the other hand,
When the rotational speed of the internal combustion engine is a low rotational speed smaller than a predetermined low rotational speed threshold smaller than the high rotational speed threshold, among the amount of fuel determined according to the load required for the internal combustion engine, Fuel is injected by the fuel injection means so that an amount of fuel required for self-ignition and combustion of the mixed gas formed in the second space accompanying the compression due to the movement of the piston is included in the mixed gas. It is preferable to provide a fuel injection control means for injecting fuel.

  When the piston is in the vicinity of the top dead center position, the temperature of the mixed gas in the combustion chamber compressed by the piston is high. The mixed gas in the combustion chamber is self-ignited when a high temperature state in which the temperature of the mixed gas is higher than a predetermined threshold temperature continues for a predetermined time. By the way, in the high speed operation region, since the time during which the piston is in the vicinity of the top dead center position is short, the time during which the mixed gas in the combustion chamber is in a high temperature state is also shortened. For this reason, there is a possibility that the mixed gas in the combustion chamber is not self-ignited (fires out).

  On the other hand, according to the above configuration, in the high-rotation operation region, the amount of fuel necessary for self-ignition of the mixed gas is included in the mixed gas in the first space that reaches the high temperature state earlier. Thereby, the ignitability of the mixed gas in the first space can be further improved. As a result, the mixed gas in the first space can be surely self-ignited.

  On the other hand, in the low-rotation operation region, since the time that the piston is in the vicinity of the top dead center position is long, the high-temperature state of the mixed gas in the combustion chamber remains at a predetermined time before the piston reaches the top dead center position. Continued state. For this reason, there exists a possibility that the mixed gas in the 1st space which will be in a high temperature state sooner may be self-ignited too early.

  On the other hand, according to the above-described configuration, in the low-rotation operation region, the amount of fuel necessary for self-ignition of the mixed gas is included in the mixed gas in the second space that becomes a higher temperature state later. Thereby, since the amount of fuel contained in the mixed gas in the first space is reduced, the spatial distribution density of the fuel in the first space can be lowered. As a result, it is possible to prevent the same mixed gas in the first space from being self-ignited prematurely.

  In this case, the cylinder head, the piston, and the fuel injection means are arranged such that the position of the piston at the timing at which fuel is injected by the fuel injection means is closer to the bottom dead center position, the first of the fuels to be injected. It is preferable that the amount of fuel contained in the mixed gas formed in one space is increased.

  If the injected fuel is not sufficiently vaporized, the mixed gas is not self-ignited. In order for the fuel to be vaporized, a predetermined time is required. By the way, in the high speed operation region, the time from when the fuel is injected until the piston reaches the compression top dead center is extremely short. For this reason, the injected fuel is not easily vaporized, and even if the mixed gas in the first space contains an amount of fuel necessary for self-ignition of the mixed gas in the first space, The mixed gas may not be ignited.

  On the other hand, according to the above configuration, the more the position of the piston corresponding to the timing at which the fuel is injected is closer to the bottom dead center position side, the more fuel is included in the mixed gas formed in the first space. The amount of fuel to be increased. Therefore, for example, in the high rotation operation region, in order to include a large amount of fuel in the mixed gas in the first space, the fuel is injected when the position of the piston is sufficiently on the bottom dead center position side. As a result, the time required for the injected fuel to be sufficiently vaporized is secured, so that the mixed gas can be surely self-ignited in the first space.

In addition, the cylinder head, the piston, and the fuel injection unit of the internal combustion engine may be mixed gas formed in the two spaces by changing the timing of fuel injection by the fuel injection unit. Configured to vary the amount of fuel included, and
The fuel injection control means performs a plurality of times for one combustion cycle so as to control the amount of fuel contained in the mixed gas respectively formed in the two spaces according to the operating state of the internal combustion engine. It is preferable that the fuel is injected by the fuel injection means at different timings.

  According to this, the amount of fuel contained in the mixed gas formed in each of the two spaces is controlled according to the operating state of the internal combustion engine. Thereby, the timing at which the mixed gas in each space is self-ignited can be appropriately controlled. As a result, for example, between the timing at which the thermal energy generated per unit time by combustion in the first space becomes maximum and the timing at which the thermal energy generated per unit time by combustion in the second space becomes maximum. Fuel consumption can be improved by controlling the timing at which the mixed gas in each space is self-ignited so that the timing coincides with the timing at which the piston position becomes the top dead center position.

On the other hand, the fuel injection means includes two fuel injection valves that respectively face each of the two spaces and inject fuel independently toward the surface for configuring the spaces,
The fuel injection control means is provided from each of the two fuel injection valves so as to control the amount of fuel contained in the mixed gas respectively formed in the two spaces according to the operating state of the internal combustion engine. It is preferable to inject a certain amount of fuel.

  According to this, substantially all of the fuel injected from each fuel injection valve is retained in the space where the fuel injection valve faces. Thereby, while being able to control the quantity of the fuel contained in each of the mixed gas in two spaces, the timing which injects a fuel can be changed. As a result, for example, in the high-rotation operation region, the mixed gas in the first space that becomes a high temperature state earlier can include the amount of fuel necessary for the same mixed gas to self-ignite and By injecting the fuel at an early stage, it is possible to secure the time necessary for the injected fuel to be sufficiently vaporized. As a result, the mixed gas can be surely self-ignited in the first space.

  An internal combustion engine according to the present invention includes a cylinder block in which a cylinder bore is formed, a cylinder head disposed above the cylinder block, a piston that reciprocates in the cylinder bore, at least a wall surface of the cylinder bore, and the cylinder head. A fuel injection means for injecting fuel supplied to a combustion chamber constituted by a lower surface of the piston and a top surface of the piston, and an ignition plug arranged on the cylinder head to generate a spark so as to face the combustion chamber. Prepare.

  The internal combustion engine according to the present invention is operated by a spark ignition system in which a mixed gas containing air and fuel is formed in the combustion chamber in a part of the operation region, and the mixed gas is ignited by a spark generated by the spark plug and burned. In a different operation region, a mixed gas containing air, fuel and combustion gas is formed in the combustion chamber, and the mixed gas is compressed to perform self-ignition and combustion so as to burn.

  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. It is comprised so that it may become larger than the 2nd space volume ratio which is ratio of the volume of the said 2nd space when the same piston with respect to the volume of this is in the same predetermined position.

The internal combustion engine according to the present invention includes an operation method selection means, a fuel injection control means, and a switching fuel injection correction means.
The operation method selection means selects one of the premixed compression self-ignition method and the spark ignition method according to the operation state of the internal combustion engine.

  The fuel injection control means includes an injected fuel amount that is an amount of fuel injected by the fuel injection means based on a load required for the internal combustion engine and the selected operation method, and the fuel injection means The fuel injection timing, which is the timing at which the fuel is injected, is determined, and fuel is injected by the fuel injection means based on the determined injected fuel amount and the fuel injection timing.

  The fuel injection correction means at the time of switching, when switching the operation method from the spark ignition method to the premixed compression auto-ignition method, the fuel contained in the mixed gas in the first space in the first combustion cycle immediately after the switching of the operation method The spatial fuel ratio, which is the ratio of the amount of fuel contained in the mixed gas in the second space to the amount of fuel, is determined when the fuel injection control means determines the amount of fuel injected and the fuel injection timing in the combustion cycle. The determined ratio is set to be larger than the same space fuel ratio at the time when the operation by the premixed compression auto-ignition method is regularly performed under the same load as that required for the internal combustion engine. The injected fuel amount and the fuel injection timing are corrected.

  During the self-ignition operation, a large amount of combustion gas is introduced into the combustion chamber in order to increase the temperature of the mixed gas and improve the ignitability. By the way, the air-fuel ratio of the mixed gas at the time of operation by the spark ignition method (spark ignition operation) is smaller than the air-fuel ratio at the time of self-ignition operation (for example, the theoretical air-fuel ratio). Therefore, the temperature of the combustion gas generated by the combustion during the spark ignition operation is higher than the temperature of the combustion gas during the self-ignition operation.

  For this reason, when the operation method is switched from the spark ignition method to the premixed compression self-ignition method, the temperature of the mixed gas into which the combustion gas is introduced in the first combustion cycle immediately after the switching is constantly performing the self-ignition operation. Higher than the case. As a result, there is a risk that the mixed gas in the first space, which becomes a high temperature state earlier, is pre-ignited too early.

  On the other hand, according to the above configuration, when the combustion cycle is the first combustion cycle immediately after switching the operation method from the spark ignition method to the premixed compression auto-ignition method, the fuel contained in the mixed gas in the first space The fuel is injected such that the space fuel ratio, which is the ratio of the amount of fuel contained in the mixed gas in the second space to the amount of the above, is larger than that in the case where the self-ignition operation is constantly performed. As a result, the mixed gas in the first space, which becomes a high temperature state sooner, includes a smaller amount of fuel than in the case where the self-ignition operation is constantly performed. As a result, since the spatial distribution density of the fuel in the first space is lowered, it is possible to prevent the mixed gas in the first space from being self-ignited prematurely.

(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 (four-cylinder) internal combustion engine that can be operated by switching between a 4-cycle premixed compression auto-ignition system and a 4-cycle spark 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 FIGS. 1 and 2, the top surface of the piston 22 is the distance in the central axis direction of the cylinder 21 from the reference position (for example, the crank pin position or the lower end portion) of the piston 22 to the top surface of the piston 22. The piston upper portion 22a is long and the piston lower portion upper surface 22b is short.

  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, a first spark plug 35a, An igniter 36 including an ignition coil for generating a high voltage to be applied to the second spark plug 35b, the first spark plug 35a and the second spark plug 35b, and a fuel injection valve (fuel injection means) 37 for directly injecting fuel into the combustion chamber 25. It has. The intake valve drive mechanism 32a and the exhaust valve drive mechanism 34a are connected to a drive circuit 38.

  As shown in FIGS. 1 and 2, the lower surface of the cylinder head portion 30 has a cylinder head high portion lower surface 30 a 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. And a cylinder head lower portion lower surface 30b having 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 smaller 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 (first space) as one independent space. Furthermore, the lower combustion chamber 25b (second 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 (first space) and a low combustion chamber 25b (second 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 high combustion chamber 25a when the piston 22 is at the combustion chamber split 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. The high combustion chamber volume ratio (first space volume ratio) VH0 / VH1, which is the ratio of the volume VH0, is the same as that of the piston 22 with respect to the volume VL1 of the low combustion chamber 25b when the piston 22 is at the top dead center position. It is larger than the lower combustion chamber volume ratio (second space volume ratio) VL0 / VL1, which is the ratio of the volume VL0 of the lower combustion chamber 25b at the combustion chamber division piston position.

  Therefore, when the mixed gas in the combustion chamber 25 is compressed by moving the piston 22 from the combustion chamber division piston position to the top dead center position, the mixed gas in the high combustion chamber 25a is mixed in the low combustion chamber 25b. Compressed more than gas, resulting in 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 first spark plug 35a 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 35b is disposed in the cylinder head portion 30 at a position between the two intake ports 31 (therefore, the two intake valves 32). Each of the first spark plug 35 a and the second spark plug 35 b includes a tip portion that generates an ignition spark, and the tip portions are exposed to the combustion chamber 25.

  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 is configured to inject fuel toward the approximate center of the combustion chamber 25. 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 includes a self-ignition operation execution means F1 including a fuel injection control means, a spark ignition operation execution means F2 including a fuel injection control means, and an operation switching means G1 including an operation method selection means. Etc. 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 G1 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 premixed compression auto-ignition method and a spark ignition method are designated as operation methods. In this operation region map, the self-ignition operation region A, which is an operation region in which the premixed compression self-ignition method is designated, is a load region smaller than a predetermined extremely high load threshold in all operation regions, and a predetermined region. This is a region of the rotational speed smaller than the extremely high rotational speed threshold. Further, in this operation region map, the spark ignition operation region B, which is the operation region in which the spark ignition method is designated, is a region on the higher load side or the higher rotation speed side than the self-ignition operation region A.

  Further, the self-ignition operation region A includes a high-load self-ignition operation region A1, a medium-load self-ignition operation region A2, a light-load self-ignition operation region A3, a high-speed self-ignition operation region A4, and a low-rotation self-ignition operation. It consists of area A5.

  The high-load self-ignition operation region A1 is a high-load region (high-load operation region) that is a load equal to or higher than a predetermined high-load threshold in the self-ignition operation region A. The medium load self-ignition operation region A2 is a medium load region (medium load operation) that is smaller than the high load threshold in the self-ignition operation region A and is equal to or higher than a predetermined light load threshold smaller than the high load threshold. A region of medium rotation speed that is a part of the region) and is smaller than a predetermined high rotation speed threshold and greater than or equal to a predetermined low rotation speed threshold smaller than the high rotation speed threshold (medium rotation operation region) It is.

  The light load self-ignition operation region A3 is a light load region (light load operation region) that is a load smaller than the light load threshold. The high rotation self-ignition operation region A4 is a high rotation speed region (high rotation operation region) that is a rotation speed equal to or higher than the high rotation speed threshold in the medium load operation region. The low-rotation self-ignition operation region A5 is a low-rotation speed region (low-rotation operation region) that is a rotation speed smaller than the low-rotation speed threshold in the medium-load operation region.

  The operation switching means G1 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 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 high-load self-ignition operation region A1)
When the internal combustion engine 10 is operated in the high-load self-ignition operation region A1 (during high-load self-ignition operation), the operation switching unit G1 selects the self-ignition operation execution unit F1 according to the operation region map. Thereby, the internal combustion engine 10 is operated by the self-ignition operation executing means F1.

  In the combustion chamber 25 (the high combustion chamber 25a and the low combustion chamber 25b), the self-ignition operation execution means F1 uses the air introduced into the combustion chamber 25, the fuel injected from the fuel injection valve 37, and the combustion gas. By compressing the mixed gas while forming the mixed gas, the mixed gas is self-ignited and burned. More specifically, the self-ignition operation execution means F1 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 F1 drives the exhaust valve drive mechanism 34a to open the exhaust valve 34 at the self-ignition exhaust valve opening timing EO corresponding to the load of the internal combustion engine 10 ((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 F1 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 F1 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. Thus, the negative overlap period which is a period from the time when exhaust ends to the time when intake starts is provided. As a result, combustion gas remains in the combustion chamber 25. The remaining combustion gas is present more in the vicinity of the exhaust valve 34 than in the vicinity of the intake valve 32.

  Next, the self-ignition operation execution means F1 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 F1 opens the fuel injection valve 37, so that the fuel is produced at the timing when the crank angle becomes BTDC135 ° (timing indicated by the one-dot broken line with A1 in FIG. 7) 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 mixed gas 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 considerably small. Therefore, as shown in FIG. 8A, approximately half of the injected fuel stays in the space above the lower piston upper 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. 8B, 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, the mixed gas which has the spatial distribution density of a substantially equal fuel is each formed in the high part combustion chamber 25a and the low part combustion chamber 25b. Moreover, in the high combustion chamber 25a where the exhaust valve 34 faces, a mixed gas containing more combustion gas than the low combustion chamber 25b is formed.

  When the piston 22 approaches the top dead center position, the mixed gas in the high combustion chamber 25a that contains more combustion gas and is compressed to a greater degree is quickly brought to a high temperature state, so that the mixing in the low combustion chamber 25b is performed. It is ignited before gas. Thereafter, when the piston 22 further approaches the top dead center position, the mixed gas is self-ignited in the lower combustion chamber 25b.

  A curve C1 indicated by a solid line in FIG. 9 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 the combustion of the mixed gas. As shown by the curve C1, the generated heat energy has a peak caused by combustion in the high combustion chamber 25a and a peak caused by combustion in the low combustion chamber 25b at two different crank angles. 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 mixed gas is self-ignited and burned at once (within a very short period of time) (see the curve C2 shown by the broken line in FIG. 9). 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, the internal combustion engine 10 is self-ignited in the high-load self-ignition operation region A1.

(When the internal combustion engine 10 is operated in the medium load self-ignition operation region A2 or the low rotation self-ignition operation region A5)
On the other hand, the case where the internal combustion engine 10 is operated in the medium load self-ignition operation region A2 or the low rotation self-ignition operation region A5 (at the time of medium load self-ignition operation or low rotation self-ignition operation) will be described. At this time, the internal combustion engine 10 is operated by the self-ignition operation execution means F1 in the same manner as in the high load self-ignition operation.

  The self-ignition operation execution means F1 at the time of medium load self-ignition operation or low-rotation self-ignition operation delays the timing of fuel injection with respect to the self-ignition operation execution means F1 at the time of high load self-ignition operation. Only the difference. Therefore, the following description will focus on such differences.

  The self-ignition operation execution means F1 closes the intake valve 32 to complete the intake and start the compression of the gas composed of the air and the combustion gas, and the timing when the crank angle becomes BTDC 120 ° ( The fuel is injected by opening the fuel injection valve 37 (see timing (5)) at θinj at a timing indicated by a one-dot broken line with A2 and A5 in FIG. 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 mixed gas in the combustion chamber 25 is an ultra lean 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 stays in the space above the piston lower surface 22b by being blocked by the piston top vertical wall surface 22c, as shown in FIG. The remaining small amount of 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 lower combustion chamber 25b, a mixed gas containing a fuel having a spatial distribution density higher than the spatial distribution density of the fuel in the high combustion chamber 25a is formed.

  Therefore, during the medium load self-ignition operation, the spatial fuel ratio, which is the ratio of the amount of fuel contained in the mixed gas in the low combustion chamber 25b to the amount of fuel contained in the mixed gas in the high combustion chamber 25a, is It is larger than the same space fuel ratio in high load self-ignition operation.

  When the piston 22 approaches the top dead center position, first, the mixed gas in the high combustion chamber 25a is self-ignited, and immediately thereafter, the mixed gas is self-ignited in the low combustion chamber 25b.

  As described above, the timing at which the mixed gas in the high combustion chamber 25a is self-ignited is compared with the case where the space fuel ratio in the medium load self-ignition operation is equal to the space fuel ratio in the high load self-ignition operation. On the other hand, the timing at which the mixed gas in the lower combustion chamber 25b is self-ignited shifts to the advance side.

  Thus, in the medium load operation region where there is little risk of excessive noise generation, the timing at which the mixed gas in the high combustion chamber 25a is self-ignited and the mixed gas in the low combustion chamber 25b is self-ignited. The ignition timing interval between the ignition timing and the ignition timing becomes smaller than the ignition timing interval in the high load operation region. As a result, the equal volume can be increased, and the fuel efficiency can be improved.

  Further, the timing at which the mixed gas in the high combustion chamber 25a is self-ignited is retarded as compared with the case where the fuel spatial distribution density in each of the high combustion chamber 25a and the low combustion chamber 25b is equal to each other. Transition. Therefore, in the low-rotation operation region, it is possible to prevent the mixed gas in the high combustion chamber 25a that reaches a high temperature state earlier from being self-ignited.

  Thus, the internal combustion engine 10 is self-ignited in the medium load self-ignition operation region A2 or the low-rotation self-ignition operation region A5.

(When the internal combustion engine 10 is operated in the light load self-ignition operation region A3 or the high rotation self-ignition operation region A4)
On the other hand, the case where the internal combustion engine 10 is operated in the light load self-ignition operation region A3 or the high rotation self-ignition operation region A4 (during light load self-ignition operation or high rotation self-ignition operation) will be described. At this time, the internal combustion engine 10 is operated by the self-ignition operation execution means F1 in the same manner as in the high load self-ignition operation.

  The self-ignition operation execution means F1 in the light load self-ignition operation or the high-speed self-ignition operation advances the timing at which fuel is injected with respect to the self-ignition operation execution means F1 in the high load self-ignition operation. Only the difference. Therefore, the following description will focus on such differences.

  The self-ignition operation execution means F1 closes the intake valve 32, thereby completing the intake air and starting the compression of the gas composed of the air and the combustion gas, and the timing when the crank angle becomes BTDC 150 ° ( The fuel is injected by opening the fuel injection valve 37 (see timing (indicated by (5))) θinj at a timing indicated by a one-dot broken line with A3 and A4 in FIG. 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 mixed gas in the combustion chamber 25 is an ultra lean air-fuel ratio.

  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 sufficiently large. Therefore, most of the injected fuel reaches the space above the piston upper surface 22a without being blocked by the piston top vertical wall surface 22c, as shown in FIG. The remaining small amount of fuel stays in the space above the lower piston upper surface 22b.

  Thereafter, as shown in FIG. 11B, 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, a mixed gas containing a fuel having a spatial distribution density higher than that of the fuel in the low combustion chamber 25b is formed.

  In this case, since the fuel is injected relatively early, it is sufficiently vaporized until the piston 22 reaches the vicinity of the top dead center position. Therefore, when the piston 22 approaches the top dead center position, the mixed gas in the high combustion chamber 25a that contains more combustion gas and is compressed to a greater extent is quickly brought to a high temperature state, so that the mixing in the low combustion chamber 25b is performed. It is ignited before gas. As described above, the mixed gas in the high combustion chamber 25a can be surely self-ignited in the light load operation region and the high rotation operation region where misfire is likely to occur.

Thereafter, the mixed gas is self-ignited in the lower combustion chamber 25b. When the mixed gas is not self-ignited in the lower combustion chamber 25b, the high-temperature and high-pressure combustion gas generated in the high combustion chamber 25a is generated when the piston 22 moves from the combustion chamber division piston position to the bottom dead center position. As a result, the mixed gas that was not self-ignited in the lower combustion chamber 25b is compressed and heated. Thereby, the same mixed gas in the lower combustion chamber 25b is combusted.
In this manner, the internal combustion engine 10 is self-ignited in the light load self-ignition operation region A3 or the high-speed self-ignition operation region A4.

(When the internal combustion engine 10 is operated in the spark ignition operation region B)
When the internal combustion engine 10 is operated in the spark ignition operation region B (at the time of spark ignition operation), the operation switching means G1 selects the spark ignition operation execution means F2 according to the operation region map. Thereby, the internal combustion engine 10 is operated by the spark ignition operation execution means F2.

  The spark ignition operation execution means F2 is a mixed gas containing air introduced into the combustion chamber 25 and fuel injected from the fuel injection valve 37 in the combustion chamber 25 (the high combustion chamber 25a and the low combustion chamber 25b). The compressed mixed gas is compressed by sparks for ignition generated by the first spark plug 35a and the second spark plug 35b, which are spark generating means, and the mixed gas is spark ignited. Burn. More specifically, as shown in FIG. 12, the spark ignition operation execution means F2 includes an intake valve drive mechanism 32a, an exhaust valve drive mechanism 34a, a first spark plug 35a, a second spark plug 35b, and a fuel injection valve. 37 is operated to operate the internal combustion engine 10.

  First, the spark ignition operation execution means F2 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 ((1 ). Thereby, exhaust of the combustion gas produced | generated by the combustion in the last combustion cycle starts. Next, the spark ignition operation execution means F2 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 ((2 ). Thereby, exhaust ends.

  Thereafter, the spark ignition operation execution means F2 opens the intake valve 32 at the spark ignition intake valve opening timing IO corresponding to the load of the internal combustion engine 10 by driving the intake valve drive mechanism 32a ((3 ). During the spark ignition operation, the combustion gas to be included in the mixed gas is not required as much as during the self-ignition operation, so the negative overlap period is set to be shorter than the same period during the self-ignition operation. For this reason, the spark ignition intake valve opening timing IO is set to be on the more advanced side than the self-ignition intake valve opening timing IO. Thereby, inhalation is started.

  Then, the spark ignition operation execution means F2 opens the fuel injection valve 37 so that the initial stage of 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, and / or Alternatively, the fuel is injected at the middle 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 rotational speed NE so that the air-fuel ratio of the mixed gas in the combustion chamber 25 is the stoichiometric air-fuel ratio. The injected fuel is uniformly distributed in the combustion chamber 25 by the flow of air subsequently sucked into the combustion chamber 25.

  Next, the spark ignition operation execution means F2 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 5).). 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 in order to avoid knocking that tends to occur when the mixed gas is greatly compressed. . As a result, the intake air is finished and the compression of the mixed gas containing fuel and air is started.

  Next, the spark ignition operation execution means F2 emits sparks for ignition from the tip ends of the first spark plug 35a and the second spark plug 35b at the ignition timing θig at which the position of the piston 22 is in the vicinity of the top dead center position. The mixed gas is ignited by a spark (by spark ignition) and burned (see (6)). At this time, the spark ignition operation execution means F2 determines the ignition timing θig based on the load of the internal combustion engine 10 and the engine speed NE. The ignition timing by the first ignition plug 35a and the ignition timing by the second ignition plug 35b may be different timings.

Thereafter, gas expansion accompanying combustion by spark ignition begins.
In this manner, in the spark ignition operation region B, the internal combustion engine 10 is subjected to spark ignition operation.

  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. Further, in the first embodiment, the volume VH0 of the high combustion chamber 25a when the piston 22 is at the combustion chamber split 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. Ratio (first space volume ratio) VH0 / VH1 is the same as 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 25b is configured to be larger than the ratio of the volume VL0 (second space volume ratio) VL0 / VL1.

  Thereby, the mixed gas is self-ignited and burned at different timings in the two spaces. 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, etc. constituting the combustion chamber 25 is the mixed gas in the combustion chamber. Is smaller than when it is ignited and combusted at a time (within an extremely short period of time), so that the noise generated with the impact is reduced. As a result, since the self-ignition operation can be performed in a higher load operation region, the fuel consumption can be improved and the amount of NOx generated along with the combustion can be reduced.

(Second Embodiment)
Next, an internal combustion engine according to a second embodiment of the present invention will be described. In the internal combustion engine according to the second embodiment, when the combustion cycle is the first combustion cycle immediately after the operation method is switched from the spark ignition method to the premixed compression self-ignition method, the self-ignition operation execution means F1 is in the upper combustion chamber. This is different from the internal combustion engine according to the first embodiment in that the mixed gas in 25a is configured to include a smaller amount of fuel than in the case where the self-ignition operation is constantly performed. Hereinafter, this difference will be mainly described.

  As described above, the operation switching means G1 performs operation by switching the operation method from the spark ignition operation by the spark ignition operation execution means F2 to the self ignition operation by the self ignition operation execution means F1 according to the operation region map shown in FIG. . In the first combustion cycle immediately after the switching of the operation method (auto-ignition combustion cycle immediately after switching), the air-fuel ratio in the spark ignition operation is smaller than the air-fuel ratio in the auto-ignition operation, so that the auto-ignition is steadily performed. The temperature of the combustion gas introduced into the combustion chamber 25 is higher than when the operation is performed. Therefore, the temperature of the mixed gas formed in the combustion chamber 25 becomes high, and there is a possibility that the mixed gas in the high combustion chamber 25a is self-ignited prematurely.

  Therefore, when the combustion cycle is the self-ignition combustion cycle immediately after switching, the self-ignition operation execution means F1 injects the fuel at a timing retarded from the fuel injection timing shown in FIG. The spatial distribution density of the fuel is reduced to prevent the mixed gas in the high combustion chamber 25a from being self-ignited prematurely. That is, the self-ignition operation execution means F1 according to the second embodiment includes a switching time fuel injection correction means. Hereinafter, the cases will be described specifically.

(When the operating state of the internal combustion engine 10 shifts from the spark ignition operation region B to the high load self-ignition operation region A1)
In this case, when the combustion cycle is the self-ignition combustion cycle immediately after switching, the self-ignition operation execution means F1 has a crank angle of BTDC 135 ° when performing the self-ignition operation constantly in the high load self-ignition operation region A1. Instead of the timing (the timing indicated by the dashed line with A1 in FIG. 7), the timing at which the crank angle becomes BTDC 120 ° (the timing indicated by the dashed lines with A2 and A5 in FIG. 7). ), 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 mixed gas in the combustion chamber 25 is an ultra lean air-fuel ratio.

  As a result, most of the injected fuel stays in the space above the lower piston upper surface 22b (see FIG. 10A). The remaining small amount of 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 lower combustion chamber 25b, a mixed gas containing a fuel having a spatial distribution density higher than the spatial distribution density of the fuel in the high combustion chamber 25a is formed.

  Thus, the spatial fuel ratio, which is the ratio of the amount of fuel contained in the mixed gas in the low combustion chamber 25b to the amount of fuel contained in the mixed gas in the high combustion chamber 25a, is the high load autoignition operation. It is larger than the case where the self-ignition operation is constantly performed in the region A1 (see FIG. 8B). In other words, the gas mixture in the high combustion chamber 25a, which is in a high temperature state earlier, contains a smaller amount of fuel than in the case where the self-ignition operation is constantly performed in the high-load self-ignition operation region A1. As a result, since the spatial distribution density of the fuel in the high combustion chamber 25a is lowered, it is possible to prevent the mixed gas in the high combustion chamber 25a from being self-ignited prematurely.

(When the operating state of the internal combustion engine 10 shifts from the spark ignition operation region B to the medium load self-ignition operation region A2 or the low-rotation self-ignition operation region A5)
In this case, when the combustion cycle is the self-ignition combustion cycle immediately after switching, the self-ignition operation execution means F1 steadily performs the self-ignition operation in the medium load self-ignition operation region A2 or the low rotation self-ignition operation region A5. In place of the timing when the crank angle becomes BTDC 120 ° (the timing shown by the one-dot broken lines with A2 and A5 in FIG. 7), the fuel injection valve 37 becomes the timing when the crank angle becomes BTDC 100 °. The fuel is injected by opening the valve.

  As a result, the mixed gas in the high combustion chamber 25a that becomes a high temperature state sooner is less than in the case where the self-ignition operation is steadily performed in the medium load self-ignition operation region A2 or the low rotation self-ignition operation region A5. As a result, it is possible to prevent the mixed gas in the high combustion chamber 25a from being self-ignited at a timing earlier than the timing at which self-ignition occurs in the same case.

(When the operating state of the internal combustion engine 10 shifts from the spark ignition operation region B to the light load self-ignition operation region A3 or the high-speed self-ignition operation region A4)
In this case, when the combustion cycle is the self-ignition combustion cycle immediately after switching, the self-ignition operation execution means F1 steadily performs self-ignition operation in the light load self-ignition operation region A3 or the high-speed self-ignition operation region A4. In place of the timing at which the crank angle becomes BTDC 150 ° (the timing indicated by the dashed lines with A3 and A4 in FIG. 7), the timing at which the crank angle becomes BTDC 135 ° (indicated by A1 in FIG. 7). The fuel is injected by opening the fuel injection valve 37 at the timing indicated by the dashed line).

  As a result, the mixed gas in the high combustion chamber 25a, which is in a higher temperature state sooner, is less than in the case where the self-ignition operation is constantly performed in the light load self-ignition operation region A3 or the high rotation self-ignition operation region A4. As a result, it is possible to prevent the mixed gas in the high combustion chamber 25a from being self-ignited at a timing earlier than the timing at which self-ignition occurs in the same case.

  As described above, in the second embodiment of the internal combustion engine according to the present invention, when the combustion cycle is the first combustion cycle immediately after the operation method is switched from the spark ignition method to the premixed compression auto-ignition method, the high combustion chamber 25a. The space fuel ratio, which is the ratio of the amount of fuel contained in the mixed gas in the lower combustion chamber 25b to the amount of fuel contained in the inner mixed gas, is larger than that in the case of performing steady auto-ignition operation. Inject fuel. Thereby, a smaller amount of fuel is included in the mixed gas in the high combustion chamber 25a that becomes a high temperature state earlier than in the case where the self-ignition operation is constantly performed. As a result, since the spatial distribution density of the fuel in the high combustion chamber 25a becomes low, it is possible to prevent the mixed gas in the high combustion chamber 25a from being self-ignited prematurely.

(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 an internal combustion engine according to the first embodiment in that the self-ignition operation execution means F1 is configured to inject fuel at two different timings for one combustion cycle. It is different from the institution. Hereinafter, this difference will be mainly described.

  When the internal combustion engine 10 is operated in the medium load self-ignition operation region A2 or the low-rotation self-ignition operation region A5 (at the time of medium-load self-ignition operation or low-speed self-ignition operation), the internal combustion engine 10 is Similar to the embodiment, the vehicle is operated by the self-ignition operation execution means F1.

  As shown in FIG. 13, the self-ignition operation execution means F1 closes the intake valve 32 to complete the intake and start the compression of the gas composed of the air and the combustion gas. The first amount of fuel is injected by opening the fuel injection valve 37 at the first timing θinj1 at which the angle becomes BTDC 160 ° (see (5)).

  At this time, substantially all of the injected fuel reaches the space above the piston upper surface 22a without being blocked by the piston top vertical wall surface 22c, as shown in FIG.

  Then, as shown in FIG. 13, the self-ignition operation execution means F1 opens the fuel injection valve 37 at the second timing θinj2 at which the crank angle becomes BTDC 100 °, thereby increasing the first amount greater than the first amount. 2 amount of fuel is injected (see (6)). At this time, as shown in FIG. 14B, substantially all 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.

  As described above, the total amount of fuel injected in two times is determined based on the load of the internal combustion engine 10 and the engine speed NE so that the air-fuel ratio of the mixed gas in the combustion chamber 25 is the ultra lean air-fuel ratio. Amount.

  Thereafter, as shown in FIG. 14C, at the timing when the crank angle becomes BTDC 90 ° (the position of the piston 22 becomes the combustion chamber divided 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, the fuel injected at the first timing θinj1 is included in the mixed gas in the high combustion chamber 25a, and the fuel injected at the second timing θinj2 is contained in the low combustion chamber 25b. It is contained in the mixed gas. As a result, the space higher than the spatial distribution density of the fuel in the high combustion chamber 25a in the low combustion chamber 25b, as in the medium load self-ignition operation or the low-rotation self-ignition operation of the first embodiment. It is possible to form a mixed gas containing a fuel having a uniform distribution density.

  On the other hand, when the internal combustion engine 10 is operated in the light load self-ignition operation region A3 or the high-speed self-ignition operation region A4 (during light load self-ignition operation or high-speed self-ignition operation), the self-ignition operation execution means F1 is a second timing at which the first amount of fuel is injected by opening the fuel injection valve 37 at the first timing θinj1 when the crank angle becomes BTDC 160 °, and the crank angle becomes BTDC 100 °. At θinj2, the fuel injection valve 37 is opened to inject a second amount of fuel that is smaller than the first amount. At this time, the total amount of fuel injected in two times is based on the load of the internal combustion engine 10 and the engine speed NE so that the air-fuel ratio of the mixed gas in the combustion chamber 25 is an ultra lean air-fuel ratio. It is a fixed amount.

  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 Thereby, the fuel injected at the first timing θinj1 is included in the mixed gas in the high combustion chamber 25a, and the fuel injected at the second timing θinj2 is contained in the low combustion chamber 25b. It is contained in the mixed gas. As a result, as in the light load self-ignition operation or the high-speed self-ignition operation of the first embodiment, the space higher than the spatial distribution density of the fuel in the low combustion chamber 25b in the high combustion chamber 25a. It is possible to form a mixed gas containing a fuel having a uniform distribution density.

  Further, when the internal combustion engine 10 is operated in the high-load self-ignition operation region A1 (during high-load self-ignition operation), the self-ignition operation execution means F1 has a first timing θinj1 at which the crank angle becomes BTDC 160 °. Then, the first amount of fuel is injected by opening the fuel injection valve 37, and the first time by opening the fuel injection valve 37 at the second timing θinj2 at which the crank angle becomes BTDC 100 °. A second amount of fuel approximately equal to the amount of. At this time, the total amount of fuel injected in two times is based on the load of the internal combustion engine 10 and the engine speed NE so that the air-fuel ratio of the mixed gas in the combustion chamber 25 is an ultra lean air-fuel ratio. It is a fixed amount.

  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 Thereby, the fuel injected at the first timing θinj1 is included in the mixed gas in the high combustion chamber 25a, and the fuel injected at the second timing θinj2 is contained in the low combustion chamber 25b. It is contained in the mixed gas. As a result, similarly to the high load self-ignition operation of the first embodiment, mixed gases having substantially the same spatial distribution density of fuel can be formed in the high combustion chamber 25a and the low combustion chamber 25b, respectively. it can.

  Thus, in the third embodiment of the internal combustion engine according to the present invention, fuel is injected from the fuel injection valve 37 at two different timings for one combustion cycle. Thus, the amount of fuel contained in the mixed gas formed in each of the two spaces is controlled according to the operating state of the internal combustion engine. As a result, it is possible to appropriately control the timing at which the mixed gas in each space is self-ignited.

  In the third embodiment, fuel is injected from the fuel injection valve 37 at two different timings for one combustion cycle. However, the fuel is injected at three or more different timings. It may be injected.

(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 is different from the internal combustion engine according to the first embodiment in that the fuel injection means includes two fuel injection valves facing the two spaces of the divided combustion chambers. . Hereinafter, this difference will be mainly described.

  As shown in FIG. 15, the internal combustion engine includes a first fuel injection valve 81a and a second fuel injection valve 81b as fuel injection means instead of the fuel injection valve 37.

  The first fuel injection valve 81 a is a side wall surface of the combustion chamber 25 on the cylinder head high portion lower surface 30 a side, and is a straight line that is perpendicular to the plane formed by the cylinder head vertical wall surface 30 c and passes through the central axis of the cylinder 21. It is arranged in the upper position. The first fuel injection valve 81a is configured to inject fuel toward the cylinder head vertical wall surface 30c, which is a surface for constituting the high combustion chamber 25a.

  The second fuel injection valve 81b is the lower surface 30b of the cylinder head lower portion, which is orthogonal to the plane formed by the cylinder head vertical wall surface 30c and is on the bore wall surface side of the cylinder 21 on a straight line passing through the central axis of the cylinder 21. It is arranged at the position. The second fuel injection valve 81b is configured to inject fuel toward the piston lower portion upper surface 22b, which is a surface for constituting the lower combustion chamber 25b.

  Fuel in a fuel tank (not shown) is supplied to the first fuel injection valve 81a and the second fuel injection valve 81b by a fuel pressure adjusting means (not shown) and a fuel pump, respectively.

  With such a configuration, the fuel injected from the first fuel injection valve 81a is retained in the space above the piston high portion upper surface 22a, while the fuel injected from the second fuel injection valve 81b is low in the piston low level. It is made to stay in the space above part upper surface 22b.

  When the internal combustion engine 10 is operated in the light load self-ignition operation region A3 or the high-speed self-ignition operation region A4 (during light load self-ignition operation or high-speed self-ignition operation), the self-ignition operation execution means F1 As shown in FIG. 15A, the first fuel injection valve 81a and the second fuel injection valve 81b are each opened at the timing θinj at which the crank angle becomes BTDC 160 °, whereby the first fuel injection is performed. A first amount of fuel is injected from the valve 81a, and a second amount of fuel smaller than the first amount is injected from the second fuel injection valve 81b. At this time, the total amount of fuel injected from each of the first fuel injection valve 81a and the second fuel injection valve 81b is such that the air-fuel ratio of the mixed gas in the combustion chamber 25 is an ultra lean air-fuel ratio. The amount is determined based on the load and the engine speed NE.

  Thereafter, as shown in FIG. 15B, 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, the fuel injected from the first fuel injection valve 81a is included in the mixed gas in the high combustion chamber 25a, and the fuel injected from the second fuel injection valve 81b is included in the low combustion chamber 25b. It is contained in the mixed gas.

  As a result, as in the light load self-ignition operation or the high-speed self-ignition operation of the first embodiment, the space higher than the spatial distribution density of the fuel in the low combustion chamber 25b in the high combustion chamber 25a. It is possible to form a mixed gas containing a fuel having a uniform distribution density. Further, since the fuel is injected at a sufficiently early timing when the crank angle becomes BTDC 160 °, the injected fuel can be sufficiently vaporized. As a result, the mixed gas in the high combustion chamber 25a can be self-ignited more reliably.

  On the other hand, when the internal combustion engine 10 is operated in the medium load self-ignition operation region A2 or the low-rotation self-ignition operation region A5 (at the time of medium-load self-ignition operation or low-speed self-ignition operation), the self-ignition operation execution means F1 opens the first fuel injection valve 81a and the second fuel injection valve 81b at the timing θinj at which the crank angle becomes BTDC 160 °, thereby allowing the first amount of fuel to be discharged from the first fuel injection valve 81a. In addition to the injection, a second amount of fuel greater than the first amount is injected from the second fuel injection valve 81b. At this time, the total amount of fuel injected from each of the first fuel injection valve 81a and the second fuel injection valve 81b is such that the air-fuel ratio of the mixed gas in the combustion chamber 25 is an ultra lean air-fuel ratio. The amount is determined based on the load and the engine speed NE.

  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 Thereby, the fuel injected from the first fuel injection valve 81a is included in the mixed gas in the high combustion chamber 25a, and the fuel injected from the second fuel injection valve 81b is included in the low combustion chamber 25b. It is contained in the mixed gas. As a result, the space higher than the spatial distribution density of the fuel in the high combustion chamber 25a in the low combustion chamber 25b, as in the medium load self-ignition operation or the low-rotation self-ignition operation of the first embodiment. It is possible to form a mixed gas containing a fuel having a uniform distribution density.

  Further, when the internal combustion engine 10 is operated in the high-load self-ignition operation region A1 (during high-load self-ignition operation), the self-ignition operation execution means F1 performs the first operation at the timing θinj when the crank angle becomes BTDC 160 °. The first fuel injection valve 81a and the second fuel injection valve 81b are each opened to inject a first amount of fuel from the first fuel injection valve 81a, and from the second fuel injection valve 81b to the first amount. A substantially equal second amount of fuel is injected. At this time, the total amount of fuel injected from each of the first fuel injection valve 81a and the second fuel injection valve 81b is such that the air-fuel ratio of the mixed gas in the combustion chamber 25 is an ultra lean air-fuel ratio. The amount is determined based on the load and the engine speed NE.

  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 Thereby, the fuel injected from the first fuel injection valve 81a is included in the mixed gas in the high combustion chamber 25a, and the fuel injected from the second fuel injection valve 81b is included in the low combustion chamber 25b. It is contained in the mixed gas. As a result, similarly to the high load self-ignition operation of the first embodiment, mixed gases having substantially the same spatial distribution density of fuel can be formed in the high combustion chamber 25a and the low combustion chamber 25b, respectively. it can.

  Thus, the fourth embodiment of the internal combustion engine according to the present invention faces each of the two spaces (the high combustion chamber 25a and the low combustion chamber 25b) of the divided combustion chambers as fuel injection means, Two fuel injection valves (a first fuel injection valve 81a and a second fuel injection valve 81b) for injecting fuel independently toward the surface for constituting each space are provided. Thereby, the fuel injected from each fuel injection valve is made to respectively stay in the space which each fuel injection valve faces. As a result, from the viewpoint of fuel vaporization and mixed gas self-ignition timing, the amount of fuel contained in each of the mixed gases in the two spaces can be controlled appropriately, and the timing for injecting the fuel can be set appropriately. Can be changed.

  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. Furthermore, each embodiment is comprised so that a 1st space volume ratio may become larger than a 2nd space volume ratio.

  Thereby, the mixed gas is self-ignited and burned at different timings in the two spaces. 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, etc. constituting the combustion chamber 25 is the mixed gas in the combustion chamber. Is smaller than when it is ignited and combusted at a time (within an extremely short period of time), so that the noise generated with the impact is reduced. As a result, since the self-ignition operation can be performed in a higher load operation region, the fuel consumption can be improved and the amount of NOx generated along with the combustion can be reduced.

  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, the piston top vertical wall surface 22c and the cylinder head vertical wall surface 30c in the above embodiments are flat surfaces, but 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 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 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, 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 opening / closing timing and fuel injection timing of the intake valve and exhaust valve of a cylinder when the internal combustion engine which concerns on 3rd Embodiment of this invention is drive | operated by a premixing 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 figure which showed typically the fuel-injection means with which 4th Embodiment of this invention is provided, and the spatial distribution of the injected fuel.

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 surface, 30c ... Cylinder head vertical wall surface, 31 ... Intake port, 32 ... Intake valve, 32a ... Intake valve drive mechanism, 33 ... Exhaust port, 34 ... Exhaust valve, 34a ... Exhaust valve drive mechanism, 35a ... First spark plug 35b ... second spark plug, 36 ... igniter, 37 ... fuel injection valve, 38 ... drive circuit, 61 ... crank position sensor, 62 An accelerator opening sensor, 70 ... electric control unit, 81a ... first fuel injection valves, 81b ... second fuel injection valve.

Claims (10)

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 supplied into a combustion chamber, an intake valve formed in the cylinder head for opening and closing an intake port for supplying air to the combustion chamber, and the combustion formed in the cylinder head An exhaust valve that opens and closes an exhaust port for discharging indoor combustion gas from the combustion chamber,
In an internal combustion engine that performs an operation by a premixed compression self-ignition method in which a mixed gas containing air, fuel, and combustion gas is formed in the combustion chamber and the mixture gas is compressed to self-ignite and burn.
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. An internal combustion engine configured to be larger than a second space volume ratio that 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 engine. The internal combustion engine according to claim 1,
The piston is formed so that the top surface of the piston has a piston top vertical wall surface that is a surface orthogonal to a plane orthogonal to the central axis of the cylinder bore,
The cylinder head is formed such that a lower surface of the cylinder head has a cylinder head vertical wall surface that is a surface orthogonal to a plane orthogonal to the central axis of the cylinder bore, and
The combustion chamber is divided into the two spaces by the piston top vertical wall surface and the cylinder head vertical wall surface facing each other when the piston is closer to the top dead center position than the predetermined position. An internal combustion engine configured as described above. The internal combustion engine according to claim 1 or 2,
The exhaust valve is arranged to face the first space,
The intake valve is an internal combustion engine arranged to face the second space. An internal combustion engine according to any one of claims 1 to 3,
When the load of the internal combustion engine is a light load that is smaller than a predetermined light load threshold, out of the amount of fuel determined according to the load required for the internal combustion engine, the compression is caused by the movement of the piston. The fuel injection means injects the fuel so that the amount of fuel required for self-ignition and combustion of the mixed gas formed in one space is included in the mixed gas,
When the load of the internal combustion engine is a medium-high load that is equal to or higher than the light load threshold, it is necessary for the mixed gas formed in each of the two spaces to be self-ignited and combusted with the compression caused by the movement of the piston. An internal combustion engine comprising fuel injection control means for injecting fuel by the fuel injection means so that an amount of fuel is included in each of the mixed gases. The internal combustion engine according to claim 4,
The fuel injection control means is a mixed gas in the first space when the load of the internal combustion engine is a medium load that is smaller than a predetermined high load threshold greater than the light load threshold and greater than or equal to the light load threshold. When the spatial fuel ratio, which is the ratio of the amount of fuel contained in the mixed gas in the second space to the amount of fuel contained in the second space, is the same space when the load of the internal combustion engine is a high load equal to or higher than the high load threshold An internal combustion engine in which fuel is injected by the fuel injection means so as to be larger than a fuel ratio. The internal combustion engine according to any one of claims 1 to 5,
When the rotational speed of the internal combustion engine is a high rotational speed that is equal to or higher than a predetermined high rotational speed threshold, out of the amount of fuel determined according to the load required for the internal combustion engine, accompanying the compression due to the movement of the piston The fuel injection means injects the fuel so that the amount of fuel necessary for self-ignition and combustion of the mixed gas formed in the first space is included in the mixed gas,
When the rotational speed of the internal combustion engine is a low rotational speed smaller than a predetermined low rotational speed threshold smaller than the high rotational speed threshold, among the amount of fuel determined according to the load required for the internal combustion engine, Fuel is injected by the fuel injection means so that an amount of fuel required for self-ignition and combustion of the mixed gas formed in the second space accompanying the compression due to the movement of the piston is included in the mixed gas. An internal combustion engine provided with fuel injection control means for injecting fuel. The internal combustion engine according to claim 6,
The cylinder head, the piston, and the fuel injection means are arranged in the first space in the injected fuel as the position of the piston at the timing of fuel injection by the fuel injection means is closer to the bottom dead center position. An internal combustion engine configured to increase the amount of fuel contained in the mixed gas formed in the above. The internal combustion engine according to any one of claims 1 to 7,
The cylinder head, the piston, and the fuel injection means change the amount of fuel contained in the mixed gas formed in each of the two spaces by changing the timing of fuel injection by the fuel injection means. And
The fuel injection control means performs a plurality of times for one combustion cycle so as to control the amount of fuel contained in the mixed gas respectively formed in the two spaces according to the operating state of the internal combustion engine. An internal combustion engine configured to inject fuel by the fuel injection means at different timings. The internal combustion engine according to any one of claims 1 to 7,
The fuel injection means includes two fuel injection valves that respectively face each of the two spaces and inject fuel independently toward a surface for forming the spaces,
The fuel injection control means is provided from each of the two fuel injection valves so as to control the amount of fuel contained in the mixed gas respectively formed in the two spaces according to the operating state of the internal combustion engine. An internal combustion engine that injects a fixed amount of fuel. 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 supplied into a combustion chamber constituted by: and a spark plug that is disposed on the cylinder head so as to face the combustion chamber and generates a spark,
In some operation regions, a gas mixture containing air and fuel is formed in the combustion chamber, and the mixture gas is ignited by the spark generated by the spark plug and burned, and the operation is performed in other operation regions. An internal combustion engine that operates in a premixed compression self-ignition system that forms a mixed gas containing air, fuel, and combustion gas in the combustion chamber and compresses the mixed gas for self-ignition and combustion.
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
An operation method selection means for selecting one of the premixed compression auto-ignition method and the spark ignition method according to the operation state of the internal combustion engine;
The amount of fuel to be injected by the fuel injection means based on the load required for the internal combustion engine and the selected operation method, and the timing at which fuel is injected by the fuel injection means A fuel injection control means for determining the fuel injection timing, and for injecting fuel by the fuel injection means based on the determined injected fuel amount and the fuel injection timing;
When the operation method is switched from the spark ignition method to the premixed compression auto-ignition method, the second space in the second space with respect to the amount of fuel contained in the mixed gas in the first space in the first combustion cycle immediately after the operation method is switched. The space fuel ratio, which is the ratio of the amount of fuel contained in the mixed gas, is required for the internal combustion engine when the fuel injection control means determines the amount of fuel injected and the fuel injection timing in the combustion cycle. The determined injected fuel amount and fuel injection timing are set so as to be larger than the same space fuel ratio at the time when the operation by the premixed compression auto-ignition method is constantly performed under the same load as Switching fuel injection correction means for correction;
An internal combustion engine.

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