JP2991182B2 - In-cylinder injection type internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-cylinder injection type internal combustion engine in which a gas flowing from an intake port into a cylinder is swirled, and then fuel is injected into the cylinder to generate a mixture and burn. About the institution.

[0002]

2. Description of the Related Art A main body of an ordinary internal combustion engine is composed of a cylinder head, a cylinder block and a crankcase stacked in this order to form a main part. The chamber accommodates an intake / exhaust passage that can communicate with the chamber via an intake / exhaust valve, a valve train that drives the intake / exhaust valve, a connecting rod that converts reciprocating motion of a piston into rotational motion and transmits the rotational motion to a crankshaft. When such an internal combustion engine is, for example, a four-stroke engine, fuel is supplied to the intake air taken into the cylinder during an intake stroke in an amount corresponding to the intake air amount to generate combustion energy, and the energy is output as rotational energy. doing. Among such internal combustion engines, there is known an in-cylinder injection type internal combustion engine capable of improving driving responsiveness by directly injecting fuel into a combustion chamber.

[0003] As this kind of in-cylinder injection type internal combustion engine,
BACKGROUND ART A diesel engine which is a compression ignition internal combustion engine and a gasoline engine which is a spark ignition internal combustion engine are known.
Among them, a diesel engine does not require an ignition means, but requires an engine capable of achieving a high compression ratio and a high-pressure fuel injection means, and has a problem in increasing its size and weight.
On the other hand, an in-cylinder injection type gasoline engine is configured as shown in FIGS. 13 and 14, for example. The gasoline engine here is of a four-valve type. A piston 51 is inserted into a cylinder S of the gasoline engine, and a pair of intake valves (not shown) is opened when the piston 51 slides from a top dead center to a bottom dead center. Air is introduced into the combustion chamber 50 from the conduction path 52 through each intake port 54, and an injector (not shown) is driven at a predetermined time during the intake and compression strokes to perform in-cylinder injection, and a spark plug 56 is driven at the end of the compression stroke. In a subsequent exhaust stroke, exhaust gas (not shown) is opened when the piston 51 rises, and an exhaust valve (not shown) is opened.
It is configured to discharge to the side.

[0004] Such a gasoline engine has few problems such as an increase in size and weight as compared with a diesel engine.

[0005]

However, such an in-cylinder injection type gasoline engine has a configuration in which respective conduction paths 52 and 53 extending from the intake / exhaust ports are respectively opened on both side walls of a cylinder head (not shown). Here, conductive paths 52 and 53 and a spark plug 56 are provided in the cylinder facing portion of the cylinder head on the upper side of the combustion chamber. In particular, the conductive paths 52 and 53 are formed large in order to ensure the volume efficiency of each cylinder. Or two intake passages 55 as shown in FIG.
When the exhaust passages 2 and 52 and the two exhaust passages 53 and 53 are provided, there is little space for securing an injector mounting portion for mounting the injector, and there are many design restrictions and it is extremely difficult to realize an optimal layout. ing.

In particular, in order to achieve stratified lean burn in a direct injection engine, the spray is collected as compactly as possible, and a rich air-fuel mixture is collected near a spark plug.
It is necessary to ensure combustion stability. However, in the conventional direct injection engine, it was almost difficult to direct the injector toward the spark plug due to the layout restriction as described above.

An object of the present invention is to provide an in-cylinder injection type internal combustion engine capable of easily securing a space for mounting an in-cylinder injector to a spark plug and improving combustion stability.

[0008]

According to a first aspect of the present invention, there is provided a combustion chamber formed between an upper surface of a piston inserted into a cylinder and a lower surface of a cylinder head. An intake port formed on one side of the cylinder head across a plane including a cylinder axis along the center of the cylinder; an exhaust port formed on the other side of the cylinder head across the plane; And an intake passage formed at the downstream end thereof communicating with the combustion chamber via the intake port, and formed in the cylinder head, and an upstream end communicated with the combustion chamber via the exhaust port. An exhaust passage, a recess formed eccentrically to either the one side or the other side of the piston upper surface, and having a convex curved surface inside the piston, and disposed on the cylinder head; A spark plug located substantially at the center of the combustion chamber, a side wall surface connected to the recess on the upper surface of the piston and protruding from the recess and extending to the side opposite to the recess, and the cylinder at a piston top dead center A flat slope that is close to the lower surface of the head and extends so as to intersect the side wall surface; a peak formed by the intersection of the side wall surface and the slope is near the ignition plug at the piston top dead center; And an injection hole disposed in a peripheral area of the combustion chamber on the concave side of the cylinder head for directly injecting fuel into the combustion chamber and pointing downward from the ignition plug. In the vicinity of the top dead center of the piston, a compact combustion chamber is formed by the recess and the side wall surface of the piston and the lower surface of the cylinder head, By guiding the fuel injected from the injector toward the recess in the contraction stroke from below the spark plug along the side wall surface to the spark plug, it is possible to ignite around the spark plug in the compact combustion chamber. It is characterized by collecting an air-fuel mixture. Further, in the second invention, a combustion chamber formed between the upper surface of the piston inserted into the cylinder and the lower surface of the cylinder head, and a plane including a cylinder axis along the center of the cylinder on the lower surface of the cylinder head. An intake port formed on one side of the cylinder head with an exhaust boat formed on the other side of the cylinder head with a plane including the cylinder axis narrowed on the lower surface of the cylinder head; And a downstream end formed in the upper cylinder head and an intake passage communicating with the combustion chamber via the intake port, and an upstream end communicated with the combustion chamber via the exhaust port. An exhaust passage, a recess formed eccentrically to either the one side or the other side of the piston upper surface, and having a convex curved surface inside the piston; A spark plug disposed substantially at the center of the combustion chamber, a side wall surface connected to the recess on the upper surface of the piston and protruding from the recess and extending to the opposite side of the flat surface, and The piston has a flat slope that is close to the lower surface of the cylinder head and extends so as to intersect with the side wall at the top dead center of the piston, and a ridge formed by the intersection of the side wall and the slope is formed on the piston. A raised portion located near the ignition plug at the dead center; and a fuel injection portion disposed in a peripheral area of the combustion chamber on the recess side of the cylinder head for directly injecting fuel into the combustion chamber and below the ignition plug. An injector having an injection hole that directs the fuel injected from the injector toward the recess in the compression stroke along the side wall surface below the spark plug. Along with guiding to the ignition plug, a squish flow generated by the slope and the lower surface of the cylinder head in the vicinity of the compression top dead center of the piston is guided to the recess side, and the fuel injected from the injector flows out to the slope side. It is characterized by suppression.

[0009]

According to the structure of the first aspect of the present invention, an edge-shaped peak is formed at the top dead center of the piston where a slope proximate to the lower surface of the cylinder head and a side wall protruding from the recess intersect. In the process, when the fuel injected from the injector into the recess reaches the edge-like ridge from the recess via the side wall surface, the fuel satisfactorily separates from the side wall surface, and the fuel injected toward the recess is removed. The fuel can be guided along the side wall surface from below the spark plug to the same spark plug.Therefore, the fuel injection timing and the fuel injection amount vary slightly from the optimum injection timing according to the engine operating state during the stratified combustion. Even if it does, the ignitable air-fuel mixture around the ignition plug in the compact combustion chamber near the piston top dead center can be collected and reliably ignited. According to the configuration of the second invention, the squish flow can be caused to flow from the slope side of the protruding portion in the vicinity of the piston compression top dead center to the recess side, and this squish flow allows the flow between the slope of the protruding portion and the lower surface of the cylinder head. Since intrusion of fuel into the gap can be prevented, discharge of unburned fuel can be reduced. Also in the second aspect of the present invention, at the piston top dead center, there is an edge-shaped peak formed by the intersection of the slope proximate to the lower surface of the cylinder head and the side wall protruding from the recess. When the fuel injected into the recess reaches the edge-like ridge from the recess via the side wall surface, the fuel is satisfactorily separated from the side wall surface, and the fuel injected toward the recess is moved along the side wall surface. Can be guided from below the spark plug to the same spark plug.Thus, even if the fuel injection timing and the fuel injection amount change slightly from the optimal injection timing according to the engine operating state during stratified combustion,
In the vicinity of the piston top dead center, ignitable air-fuel mixture is collected around the ignition plug in the compact combustion chamber, and ignition can be reliably performed.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The in-cylinder injection type internal combustion engine shown in FIGS. 1 and 2 is mounted on a two-cycle, four-valve in-cylinder injection type internal combustion engine (hereinafter simply referred to as engine E). The main body of the engine E is configured by integrally stacking a cylinder head 1 with a head cover, a cylinder block 3, a crankcase and a crank cover (not shown) in this order, and a cylinder S having a piston 2 inserted therein, Cylinder S
Intake / exhaust passages 4 that can communicate with the combustion chamber 7 consisting of the upper part of
a, 4b, 5a, 5b, a valve train (not shown) for driving a pair of intake and exhaust valves 10 and 11 for opening and closing these intake and exhaust passages, and a crank (not shown) for converting the reciprocating motion of the piston 2 into rotary motion. The shaft, the connecting rod and the like are housed. Here, since the configuration of each cylinder in the engine E is the same, a description will be mainly given of one cylinder.

Here, the cylinder head 1 has a pair of sides on one side across a plane FC (here, extending in the longitudinal direction of the head as shown in FIG. 3) including the cylinder axis L along the center of the cylinder S. The intake port 8a is connected to the other
a. The cylinder S has a cylinder S
A cylinder-facing lower wall surface 6 facing the combustion chamber 7 formed therein is formed, and the lower wall surface is formed with a long wedge-shaped recess 601 in the center thereof in the direction in which the plane FC extends. One side of the wedge-shaped recess 601, that is, one side sandwiching a plane FC including the cylinder axis, a pair of intake ports 8 a and 8 b following the pair of intake channels 4 a and 4 a, and a pair of exhaust channels 5 a on the other side. ,
Exhaust ports 9a and 9b following 5b are respectively formed (see FIGS. 1 and 5), and each port is opened and closed by an intake valve 10 and an exhaust valve 11, respectively. Further, the wedge-shaped recess 60
The ignition plug 20 is mounted at a position substantially opposite to a peak portion 232 of the raised portion 23 when the piston 2 reaches the TDC position at the substantially center position of the piston 1.

Here, the pair of exhaust passages 5a and 5b are curved and extend from the exhaust port 9a as shown in FIGS. 2 and 5, and further extend straight in a direction away from the plane FC. It is configured to open to the side wall surface.
The pair of intake passages 4a and 4b are formed on one side of the plane FC including the cylinder axis (the right side of the plane FC in FIG. 3) and extend vertically in the cylinder head 1 vertically. The downstream side communicates with each intake port 8a, and the upstream end is connected to the intake pipe 13 on the upper surface 1f of the cylinder head 1.

The intake pipes 13 connected to the intake passages 4a and 4b in a straight line have an upper end intercooler 141.
A built-in plenum chamber 14 is communicated through each branch pipe 12, and an inlet 17 of the chamber 14 is communicated with a centrifugal scavenging pump 15 having a variable speed pulley. in this way,
The intake passages 4a and 4b of the engine E and the intake pipes 1
3 has a vertically long straight shape, the flow resistance to the intake air is relatively low, and a relatively large amount of intake air is easily supplied to the combustion chamber 7, so that the volumetric efficiency of the engine can be improved.

On one side of the plane FC of the cylinder head 1, an injector mounting portion 1a is formed in a region outside the pair of intake passages 4a, and an injector 18 is mounted on the portion 1a. A high pressure pump 19 is connected to the injector 18 via a pressure accumulator 25. The high-pressure pump 19 and the injector 18 are connected to an engine controller (not shown), and a drive output is supplied to the injector for a predetermined injection time (PH, PL in FIG. 7) at a predetermined injection timing (crank angle). Have been.

In the injector mounting portion 1a, since the intake passages 4a extend upward from the intake ports 8a in a straight line, regions outside the pair of intake passages 4a are opened. Sufficient space can be secured. For this reason, the injector mounting portion 1a and the injector 18
It is easy to secure the optimum layout of the ignition plug 20
The degree of freedom is large in setting the relative orientation, position, and the like. Further, the injector mounting portion 1a is located outside the pair of intake passages 4a, so that it is relatively easy to improve the cooling performance of the injector body and the fuel, to ensure the durability of the injector, and to avoid heat damage to the fuel supply passage. It is easy to plan.

A piston 2 is inserted into the cylinder S of the first cylinder. As shown in FIG. 8, the piston 2 has a top dead center TDC indicated by a solid line and a bottom dead center BD indicated by a two-dot chain line.
Reciprocate between C. As shown in FIG. 2, the piston 2 has a skirt portion 21 and a main portion 22, and a concave portion 24 and a raised portion 23 are formed on the upper surface of the main portion 22 of the piston. Here, the concave portion 24 and the raised portion 23 are formed to promote the reverse tumble flow TF of the intake air around the parallel line LH1 of the orthogonal line LH of the cylinder axis L in the plane FC. That is, the intake air introduced from each intake port 8a so as to descend toward the top surface of the piston 2 along the cylinder wall on one side across the plane FC is applied by the side wall surface vf of the recess 24 and the raised portion 23. The intake air that is smoothly inverted and further nose-up along the other-side cylinder wall toward the lower surface of the cylinder head 1 so as to turn around an axis (LH) orthogonal to the cylinder axis L in the plane FC. Vortex generation can be promoted.

In this case, the recess 24 is formed so as to be eccentric to the exhaust port 9a side including the cylinder axis L, and at least an orthogonal view of the orthogonal line LH (a recess corresponding to the orthogonal view in FIGS. 2 and 8). 24 is shown.). The raised portion 23 is connected to the other side (the exhaust port 9a side) of the recess 24 across the plane FC, and the side wall surface v extending in a direction substantially parallel to the plane FC while facing the plane FC.
f, a flat slope 231 and a side wall face vf and a ridge 232 at a connecting end of both walls where the slope 231 intersects. In particular, as shown by the solid line in FIG.
C, when the ridge 232 is located on the lower wall 6 facing the cylinder.
Is configured to be close to The raised portion 2
3 is continuously connected to a curved surface gently rising from the recess 24.

For this reason, as shown in FIG.
Reaches the bottom dead center BDC side at the end of the intake, the intake air flowing from the intake port 8a goes to the upper surface of the piston along the direction of the axis L, and further makes a U-turn by the recess 24 and the side wall surface vf, and the cylinder axis L The orthogonal line L in the plane FC including
An inverse tumble flow TF that rotates around the parallel line LH1 of H is generated.

Further, as shown by the solid line in FIG. 8, when the piston 2 reaches the end of compression,
A compact combustion chamber C is formed between the side wall surface vf and the lower wall 6 facing the cylinder. The fuel injected into the combustion chamber C collides with the recess 24 or the recess 24 and the side wall surface vf, and the fuel spray after the collision thereafter flows along the side wall surface vf. Since the ridge 232 at the joint end of the two walls intersecting with the slope 231 is formed in an edge shape, the fuel can be easily separated, and the ridge 232 is directed toward the spark plug 20 disposed at a position facing the ridge 232. The reverse tumble flow TF flowing out and scattered and generated in the compact combustion chamber C regulates the flow of the fuel spray that has collided with the recess 24, or the recess 24 and the side wall surface vf, and ensures the flow. The fuel spray is guided to the spark plug 20 disposed at a position facing the peak 232. Further, at this time, a squish SF generated when the lower surface of the cylinder head 1 and the inclined surface 231 approach each other due to the rise of the piston 2 collides with the air-fuel mixture toward the ignition plug 20, thereby causing the lower surface of the cylinder head 1 and the inclined surface 231 to collide with each other. The mixture can be prevented from entering the space, the HC concentration can be reduced, and the mixture is further agitated by the squish SF to promote vaporization and improve the combustibility. Furthermore, the injected fuel, particularly the fuel injected in the late compression stage, is reliably received by the compact combustion chamber C by the recess 24 and the raised portion 23, and is prevented from diffusing toward the periphery of the piston. Of the fuel can be reduced, and as a result, the HC concentration in the exhaust gas can be reduced.

Since such an engine E has two cycles, as shown in FIG. 6, the previous combustion stroke is performed from TDC of 0 °, and after 90 ° in the crank angle, the exhaust valve 11 is exhausted.
To enter the exhaust stroke, and when the crank angle approaches 120 °, the intake valve 10 is also opened to enter the intake stroke.
At this time, as shown by the two-dot chain line in FIG.
The intake air flowing from b makes the U-turn of the intake air flowing downward in the direction of the cylinder axis L by the action of the recess 24 and the side wall surface vf, thereby generating a reverse tumble flow TF.

After the bottom dead center BDC has passed, the crank angle is 230 °
The exhaust valve 11 is closed near this side to start the compression stroke. At the same time, when the engine is rotating at a high speed, the injector 18 starts to be driven, and the injector is driven for injection for a predetermined injection time PH. As a result, the fuel injected into the reverse tumble flow TF is reliably mixed, and high power generation can be accurately performed. Thereafter, the intake valve 10 is also closed to complete the intake and exhaust, and only the compression stroke is completely performed. At this time, if the engine is running at a low speed, late-stage in-cylinder injection is performed for a predetermined time PL at this time.

In the latter-stage in-cylinder injection, the compact combustion chamber C
The mixture is compactly collected to form a layer, and the layered rich mixture flows to the spark plug 20 and is easily ignited and burned, thereby achieving lean burn.
In the latter-stage in-cylinder injection, it is possible to secure a super-lean burn with an air-fuel ratio of 50 or more depending on the setting of combustion conditions, and it is possible to improve the fuel efficiency by 30% at the indicated fuel efficiency. Thereafter, when the ignition timing reaches a predetermined ignition timing before the top dead center TDC, the ignition plug 20 is driven to start an ignition process (indicated by a symbol に は in FIG. 6). Due to this ignition processing, the in-cylinder pressure of the combustion chamber rises, pushing down the piston and generating an output.

Here, the injector 18 is controlled by the control means to perform the injection driving for a predetermined injection time PH when the engine is rotating at a high speed and to perform the injection driving for a predetermined injection time PL when the engine is at a low speed. Thus, at high speed, mixing of the fuel and the air forming the reverse tumble flow TF is started early to promote turbulence and achieve rapid combustion. On the other hand, at low speed, the injection is delayed and the late in-cylinder injection is executed, the generation of the compact combustion chamber C is awaited, the fuel is injected here, and the squish SF is also agitated to sufficiently secure the ignitability. be able to.

Further, the injector mounting portion 1a is located outside the pair of intake passages 4a, so that it is relatively easy to improve the cooling performance of the injector body and the fuel, to ensure the durability of the injector and to avoid heat damage. Easy to plan. At high speed, fuel injection is started early to sufficiently generate an air-fuel mixture and promote generation of high output. On the other hand, at low speed, injection is delayed to wait for the generation of a compact combustion chamber C, where fuel Injecting and receiving the stirring action of squish SF,
It is possible to sufficiently ensure ignitability and combustion stability.
Furthermore, since the compact combustion chamber C is spherical, heat loss can be reduced and low load operation can be stabilized. 1 to 5 illustrate a two-cycle gasoline engine,
Instead, the present invention may be applied to a 4-cycle gasoline engine. In this case, the same configuration of the engine body can be used, and redundant description is avoided.

In this case, as shown in FIG. 7, the four-stroke engine opens the intake valve 10 at 0 ° before TDC, enters the intake stroke, and closes the exhaust valve 11 after 0 ° of TDC. End the process. Thereafter, the piston 2 descends to a crank angle of 180 °, during which a reverse tumble flow TF is generated, and this flow is maintained until the latter half of the compression stroke. That is, the intake air that descends from the intake ports 8a and 8b toward the upper surface of the piston 2 during the intake stroke is formed by the presence of the edge-shaped peak portion 232 in addition to the recess 24 and the side wall surface vf rising from the recess 24. Flips smoothly,
Moreover, it peels off well and flows to the bottom of the cylinder head.
Pent roof-shaped cylinder head 1 as shown in FIG.
Is coupled to the intake flow descending from the intake ports 8a and 8b toward the upper surface of the piston 2 to generate a strong reverse tumble flow TF. Further, in the compression stroke, the reverse tumble flow T
F is retained, and finally the piston 2 has a depression 2
4 and the lower surface of the cylinder head 1 are held in a substantially spherical compact combustion chamber C, so that the reverse tumble flow TF generated in the intake stroke can be maintained until the latter half of the compression stroke. As shown in FIG. 7, the injection timing of the injector 18 is also performed during the compression stroke after the intake stroke has passed 210 ° and after the intake valve 10 has been closed. That is, the injector 18 is controlled so that the injection is driven at a predetermined injection time PH at the early stage of intake when the engine is rotating at a high speed, and the late in-cylinder injection is performed at the late PL of the late compression period at a low speed and low output.

Thus, for high-speed, high-load operation, mixing of the fuel and the air forming the reverse tumble flow TF is started at an early stage, so that a uniform air-fuel mixture can be formed and rapid combustion can be realized. . On the other hand, at a low speed, the injection is delayed, the generation of the compact combustion chamber C is waited, and the fuel is injected here. The squish SF is also agitated, thereby ensuring the ignitability and sufficiently achieving the lean burn. Thereafter, the squish S shown in FIG.
F also acts to further disturb the air-fuel mixture flowing from the compact combustion chamber C to the spark plug 20, thereby further improving the combustibility. When a predetermined ignition timing immediately after that is reached, the ignition plug 20 is driven to perform the ignition processing (indicated by the symbol △ in FIG. 7).
to go into. By this ignition processing, the in-cylinder pressure of the combustion chamber increases, and the expansion stroke is performed up to a crank angle of about 540 ° while depressing the piston to generate an output. Crank angle 48
In the vicinity of 0 °, the exhaust valve 11 is opened, the exhaust stroke is continued until the crank angle 720 elapses, the opening process of the intake valve 10 for the next intake stroke is performed, and four cycles are completed. In this case, the same operation and effect as in the case of two cycles can be obtained.

The intake passages 4a and 4b of the engine E shown in FIG.
Has an up-and-down shape, but an engine E1 as shown in FIGS. 9 to 11 may be used instead. The engine E1 differs from the engine E in FIG. 1 in the configuration of the intake passages 4a and 4b and the piston 2a, and differs in that the forward tumble flow TF1 is generated. The duplicate description is omitted. Here, a pair of intake ports 8a and 8b and intake passages 4c,
Reference numeral 4d denotes one side of a plane FC including the cylinder-facing lower wall surface 6 and the cylinder axis L, and the intake passages 4c and 4d extend in a direction away from the plane FC, so that the intake air flowing into the cylinder faces the cylinder. A configuration is adopted in which intake air is introduced along the lower wall surface 6 toward the other side (the exhaust port 9a, 9b side). On the other hand, the piston 2a is
1 and a main part 22, a concave part 24 'and a raised part 23' are formed on the upper surface of the main part 22 'of the piston. Here, the concave portion 24 'and the raised portion 23' are formed to promote the forward tumble flow TF1 of the intake air around the parallel line LH1 of the orthogonal line LH of the cylinder axis L in the plane FC.

In this case, the recess 24 ′ is formed eccentric to the exhaust port 9 a side including the cylinder axis L, and at least orthogonal to the orthogonal line LH when viewed in an orthogonal plane (FIG. (Indicated by '). The raised portion 23 'is connected to one side (the intake port 8a side) of the recess 24' across the plane FC, and the side wall surface v extending in a direction substantially parallel to the plane FC while facing the plane FC.
f, flat slope 231, side wall face vf and slope 231
Have a ridge 232 at the joint end of the two walls intersecting with each other. Particularly, as shown by the solid line in FIG.
When located at DC, the peak portion 232 is configured to approach the lower wall 6 facing the cylinder. In addition, the side wall surface vf of the raised portion 23 is continuously connected to a curved surface that gradually rises from the recess 24.

Therefore, as shown in FIG. 10, the intake air which the piston 2a has flown in from the intake port 8a at the end of the intake is directed to the other side (the exhaust port 9a, 9b side) along the cylinder-facing lower wall surface 6 in the cylinder S. To introduce air,
The intake air flows toward the piston upper surface along the direction of the axis L, makes a U-turn by the recess 24 ′ and the side wall surface vf, and rotates around the parallel line LH 1 of the orthogonal line LH in the plane FC including the cylinder axis L. Is generated.

Further, as shown by the solid line in FIG. 9, when the piston 2a reaches the end of compression, a compact combustion chamber C is formed. The fuel injected into the combustion chamber C is
4 'and the side wall surface vf, the spray fuel after the collision can be scattered toward the spark plug 20, and the airflow generated in the compact combustion chamber C is subjected to flow regulation and directed toward the spark plug 20. The squish SF generated on the slope 231 collides with the mixed gas flowing toward the spark plug 20, and the mixed gas is further stirred, so that the combustibility is further improved. In this case, the same operation and effect as the engine E of FIG. 1 can be obtained.

Instead of the two-cycle four-valve engine E of FIG. 1, for example, a two-cycle five-valve engine or a three-valve engine E 'shown in FIG. 12 may be constructed. In the case of the cylinder S of the three-valve engine E 'shown in FIG. 12, each of the intake passages communicates with the pair of intake ports 8a and 8b, and the exhaust passage 5' communicates with one exhaust port 9 '. Here, too, on one side of the plane FC including the cylinder axis L, there is an intake port 8a following the pair of intake passages 4a, 4b, and on the other side, an exhaust port 9 'following one exhaust passage 5'. Each port is formed with an intake valve 10 and an exhaust valve 11
Respectively opened and closed. Further, a spark plug 20 is mounted at a position facing the cylinder axis L.

[0032]

As described above, according to the structure of the first aspect of the present invention, an edge shape is formed in which the slope near the lower surface of the cylinder head and the side wall surface rising from the recess intersect at the piston top dead center. Due to the presence of the ridge, when the fuel injected from the injector into the recess during the compression stroke reaches the edge-like ridge from the recess via the side wall surface, the fuel is well separated from the side wall surface, The fuel injected toward the recess can be guided to the spark plug from below the spark plug along the side wall surface, and therefore, slightly deviates from the optimum injection timing according to the engine operating state during stratified combustion. Even if the fuel injection timing and fuel injection amount change, it is possible to collect an ignitable mixture around the ignition plug in the compact combustion chamber in the vicinity of the piston top dead center, thereby ensuring the mixture. It is possible to fire it is possible to enable stable stratified combustion. According to the second aspect of the present invention, the squish flow can be caused to flow from the slope side of the protruding portion near the piston compression top dead center to the recess side, and the squish flow allows the flow between the slope of the protruding portion and the lower surface of the cylinder head. It is possible to prevent the fuel from entering the gaps, so that the emission of unburned fuel can be reduced. Also in the second invention, the presence of the edge-shaped peak formed by the intersection of the slope near the lower surface of the cylinder head and the side wall surface protruding from the recess at the piston top dead center is present. Similar effects can be obtained.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a direct injection internal combustion engine as one embodiment of the present invention.

FIG. 2 is a side sectional view of one cylinder of the direct injection internal combustion engine of FIG. 1;

FIG. 3 is a schematic perspective view of one cylinder of the direct injection internal combustion engine of FIG. 1;

FIG. 4 is a schematic diagram viewed from A in FIG. 3;

FIG. 5 is a schematic top view of one cylinder of the direct injection internal combustion engine of FIG. 1;

FIG. 6 is an explanatory diagram of a drive cycle of the direct injection internal combustion engine of FIG. 1;

FIG. 7 is an explanatory diagram of a drive cycle of a direct injection internal combustion engine of another embodiment.

FIG. 8 is an operation explanatory view of one in-cylinder piston of the direct injection internal combustion engine of FIG. 1;

FIG. 9 is a schematic side sectional view of a main part of one cylinder of a direct injection internal combustion engine as another embodiment of the present invention.

FIG. 10 is a schematic perspective view of one cylinder of the direct injection internal combustion engine of FIG. 9;

FIG. 11 is a schematic layout view of main parts of one cylinder of the direct injection internal combustion engine of FIG. 9;

FIG. 12 is a schematic layout view of a main part of one cylinder of a direct injection internal combustion engine as another embodiment of the present invention.

FIG. 13 is a schematic side view of a main part of a conventional direct injection internal combustion engine.

14 is a schematic side view of the direct injection internal combustion engine of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cylinder head 2 Piston 3 Cylinder block 4a Intake conduction path 4b Intake conduction path 5a Exhaust conduction path 5b Exhaust conduction path 6 Lower wall opposite cylinder 7 Combustion chamber 8a Intake port 8b Intake port 9a Exhaust port 9b Exhaust port 10 Intake valve 11 Exhaust valve Reference Signs List 18 injector 20 spark plug 23 raised portion 231 slope 232 peak portion 24 recess vf side wall surface TF reverse tumble flow TF1 forward tumble flow SF squish L cylinder axis FC plane E engine S cylinder

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-58030 (JP, A) JP-A-4-224231 (JP, A) JP-A-4-128513 (JP, A) 124042 (JP, U) JP-A-3-52333 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) F02B 17/00-23/10 F02F 3/26

Claims (2)

(57) [Claims] A combustion chamber formed between an upper surface of a piston inserted into a cylinder and a lower surface of a cylinder head, and one end of the cylinder head sandwiching a plane including a cylinder axis along the center of the cylinder. An intake port formed on the other side; an exhaust port formed on the other side of the cylinder head across the plane; and a downstream end formed in the cylinder head and communicating with the combustion chamber via the intake port. And an exhaust passage formed in the cylinder head and having an upstream end communicated with the combustion chamber via the exhaust port; and one of the one or other sides of the piston upper surface. The recess is formed eccentrically and has a curved surface that is convex inside the piston. The recess is provided in the cylinder head and substantially at the center of the combustion chamber.
A spark plug located and the is connected to the concave plants in the piston top surface
A side wall surface protruding from the recess and extending to the opposite side of the flat surface from the recess,
And the lower surface of the cylinder head at the top dead center of the piston
A flat plate that is close to and extends so as to intersect the side wall surface
Formed with the side wall surface and the slope intersecting
The peak of the ignition plug at the top dead center of the piston
A raised portion located in the vicinity grayed, the nozzle hole directed to below the spark plug with disposed in a peripheral region of the recess side of the combustion chamber in the cylinder head for injecting fuel directly into the combustion chamber And an injector, wherein near the top dead center of the piston,
Compact with recess and side wall surface and above cylinder head lower surface
A combustion chamber and the above-mentioned input during the compression stroke.
The fuel injected from the ejector into the recess is
From above the spark plug along the wall
By guiding to the above compact combustion chamber
An in-cylinder injection internal combustion engine characterized by collecting an ignitable air-fuel mixture around a spark plug . 2. A combustion chamber formed between an upper surface of a piston inserted into a cylinder and a lower surface of a cylinder head, and a plane including a cylinder axis along the center of the cylinder on the lower surface of the cylinder head. An intake port formed on one side of the cylinder head; an exhaust boat formed on the other side of the cylinder head by narrowing a plane including the cylinder axis on the lower surface of the cylinder head; An exhaust passage formed at the downstream end of the cylinder head and communicating with the combustion chamber via the intake port; and an exhaust passage formed at the upstream end of the exhaust chamber with the upstream end communicated with the combustion chamber via the exhaust port. a passage, while being formed eccentrically to one of the one side or the other side of the piston top surface, a recess which exhibits a convex curved surface on the piston inside the cylinder head It is disposed, substantially at the center of the combustion chamber
A spark plug located and the is connected to the concave plants in the piston top surface
A side wall surface protruding from the recess and extending to the opposite side of the flat surface from the recess,
And the lower surface of the cylinder head at the top dead center of the piston
A flat plate that is close to and extends so as to intersect the side wall surface
Formed with the side wall surface and the slope intersecting
The peak of the ignition plug at the top dead center of the piston
A raised portion located in the vicinity grayed, the nozzle hole directed to below the spark plug with disposed in a peripheral region of the recess side of the combustion chamber in the cylinder head for injecting fuel directly into the combustion chamber An injector having a compression stroke that directs the injector from the injector to the recess.
The injected fuel along the side wall
From below to the spark plug and the piston
The slope in the vicinity of the compression top dead center of tons Shirindahe'
An in-cylinder injection type internal combustion engine , wherein a squish flow generated by the lower surface of the cylinder is guided to the recess side to prevent fuel injected from the injector from flowing out to the slope side.