JP2009162187A - Internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an internal combustion engine capable of suitably forming tumble flow while an intake valve opens. <P>SOLUTION: This engine is provided with an intake valve 34 capable of moving forward from a valve close position for closing an intake passage 30 communicating to a combustion chamber 16 to a valve open position for opening the intake passage 30 and moving backward from the valve open position to the valve close position, and a pressure increase means 45 capable of increasing pressure in the combustion chamber 16 at front in a forward direction of the intake valve 34 while the intake valve 34 opens. Since pressure difference in the combustion chamber 16 can be reduced by increasing pressure in the combustion chamber 16 right below the intake valve 34 in the forward direction while the intake valve 34 is open, intake air is not sucked near a section right under the intake valve 34 and tumble flow can be suitably formed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an internal combustion engine in which a tumble flow is formed in a combustion chamber.

  As a conventional internal combustion engine, a spark ignition direct injection engine with a supercharger that varies the lift amount of an intake valve that opens and closes an intake port communicating with a combustion chamber is known (see, for example, Patent Document 1). In this engine, by varying the lift amount of the intake valve according to the operating state of the engine, the flow rate of the air sucked into the combustion chamber is varied, and the tumble flow formed in the combustion chamber is strengthened.

JP 2003-106180 A

  By the way, conventionally, when the engine operates in a low speed region, the lift amount of the intake valve is low. In this case, the air flowing into the combustion chamber from the intake port through the intake valve flows along the wall surface of the combustion chamber, so the pressure in the combustion chamber near the intake valve is equal to the pressure on the wall surface of the combustion chamber. Compared to low pressure. Then, the air flowing along the wall surface of the combustion chamber flows toward the vicinity immediately below the intake valve due to the pressure difference, thereby generating a plurality of small vortices (turbulent flow). When a plurality of small vortices are generated, it may be difficult to form a main tumble flow.

  Therefore, an object of the present invention is to provide an internal combustion engine that can suitably form a tumble flow when the intake valve is opened.

  An internal combustion engine of the present invention is capable of advancing from a valve closing position for closing an intake passage communicating with a combustion chamber to a valve opening position for opening the intake passage, and an intake valve capable of retreating from the valve opening position to the valve closing position. And a pressure raising means capable of raising the pressure of the combustion chamber in the forward direction of the intake valve when the intake valve is opened.

  In this case, it is preferable that a fuel injection valve capable of injecting fuel into the combustion chamber is further provided, and the fuel injection valve functions as pressure increasing means.

  Further, in this case, when the intake valve is opened, the fuel injection valve injects fuel toward the combustion chamber in the forward direction of the intake valve with a low penetration force lower than a preset normal penetration force. It is preferable to perform pressure rising injection.

  On the other hand, when the intake valve is opened, the fuel injection valve may perform pressure rising injection in which fuel is injected to the end of the intake valve in the forward direction with a preset normal penetration force.

  In these cases, the lift amount from the valve closing position to the valve opening position of the intake valve is set between a preset normal lift amount and a small lift amount smaller than the normal lift amount according to the operating state of the internal combustion engine. The fuel injection valve further includes a variable amount of lift that is variable, and the fuel injection valve performs fuel injection along the flow of the tumble flow formed in the combustion chamber when the intake valve moves forward and backward by a normal lift amount, while the intake valve When the valve moves forward and backward with a small lift amount, it is preferable to perform pressure increase injection.

  In these cases, the fuel injection valve is configured to be able to inject fuel into a plurality of times during one combustion cycle. When the intake valve is opened, the fuel injection valve is in one combustion cycle. It is preferable that at least one of the total number of fuel injections in (1) is performed as pressure increase injection, and the remaining number of fuel injections is performed along the flow of the tumble flow formed in the combustion chamber.

  On the other hand, an air injection valve capable of injecting air into the combustion chamber is further provided, and the air injection valve functions as a pressure increasing means. When the intake valve is opened, the air injection valve is moved in the forward direction of the intake valve. You may perform the pressure rise injection which injects air toward the combustion chamber in the front.

  In this case, a fuel injection valve capable of injecting fuel into the combustion chamber is further provided. When the intake valve is opened, the air injection valve performs pressure rising injection, and the fuel injection valve is formed in the combustion chamber. It is preferable to perform fuel injection along the tumble flow.

  The internal combustion engine according to the present invention can reduce the pressure difference in the combustion chamber by raising the pressure in the combustion chamber immediately below the intake valve when the intake valve is opened. There is an effect that the tumble flow can be suitably formed without the drawn air being drawn near the vicinity of the intake valve.

  Hereinafter, an internal combustion engine according to the present invention will be described with reference to the accompanying drawings. Note that the present invention is not limited to the embodiments.

  Here, FIG. 1 is a schematic configuration diagram of the engine according to the first embodiment, and FIG. 2 is a diagram of the tumble flow formed in the combustion chamber when the intake valve of the conventional engine moves forward and backward with a small lift amount. It is explanatory drawing. FIG. 3 is an explanatory diagram of the tumble flow formed in the combustion chamber when the intake valve of the engine according to the first embodiment moves forward and backward with a small lift amount, and FIG. 4 shows the intake into the combustion chamber during the intake stroke. It is a graph showing the change of the flow velocity of the air to be performed. Further, FIG. 5 is an explanatory diagram of the tumble flow formed in the combustion chamber when the intake valve moves forward and backward by the normal lift amount.

  First, an internal combustion engine (hereinafter abbreviated as an engine) according to a first embodiment will be described with reference to FIG. This engine 1 is an in-cylinder injection type gasoline engine, and is controlled by an engine ECU 2.

  The engine 1 includes a crankcase 10 from the bottom, a cylinder block 11 provided at the top of the crankcase 10, and a cylinder head 12 provided at the top of the cylinder block 11 via a head gasket (not shown). Is formed. In the upper part of the cylinder block 11, a plurality of pistons 13 are accommodated in accordance with the number of cylinders (one in the drawing) so as to move up and down, and in the accommodation part formed by the lower part of the cylinder block 11 and the crankcase 10, A crankshaft 14 is accommodated. Each piston 13 and crankshaft 14 are connected by a connecting rod 15, and the vertical movement of each piston 13 is transmitted to the crankshaft 14. A plurality of pent roof type combustion chambers 16 are formed in accordance with the number of cylinders by the cylinder block 11, the cylinder head 12 and the piston 13.

  The crankcase 10 is provided with a crank angle sensor 20 that detects the rotation angle of the crankshaft 14. The crank angle sensor 20 is connected to the engine ECU 2. The engine ECU 2 determines an ignition timing by a spark plug 44 described later or a fuel injection timing by a fuel injection valve 45 described later based on the detection result of the crank angle sensor 20. I have control.

  In the cylinder block 11, a plurality of cylinder bores 24 for accommodating a plurality of pistons 13 are formed in a columnar shape. Each piston 13 is formed in a cylindrical shape so as to be fitted to each cylinder bore 24, and is supported in the cylinder bore 24 so as to be vertically movable between a top dead center and a bottom dead center. Further, a piston cavity 25 is formed in the head surface of the piston 13 so as to be immersed.

  The cylinder head 12 has two intake ports (intake passages) 30 (one in the drawing) that communicate with the combustion chambers 16 inside thereof, and two intake ports (one in the drawing) that face each intake port 30 and communicate with the combustion chambers 16. An exhaust port 31 (one in the drawing) is formed.

  In addition, two intake valves 34 are respectively provided in the two intake side communication ports 32 between the combustion chamber 16 and each intake port 30, and between the combustion chamber 16 and each exhaust port 31. Two exhaust valves 35 are disposed in the two exhaust side communication ports 33.

  Each of the intake valves 34 and each of the exhaust valves 35 is formed in a trumpet-shaped conical shape, and has a valve opening position (lower end position) that opens each of the intake side communication ports 32 and each of the exhaust side communication ports 33. Further, it is configured to be movable back and forth (up and down) between a valve closing position (upward end position) that closes each intake side communication port 32 and each exhaust side communication port 33. An intake camshaft 40 is disposed at the proximal end of the two intake valves 34, and an exhaust camshaft 41 is disposed at the proximal end of the two exhaust valves 35. By rotating 40 and 41, the two intake valves 34 and the two exhaust valves 35 can be opened and closed. That is, each intake valve 34 and each exhaust valve 35 advance from the closed position to the open position, thereby opening each intake side communication port 32 and each exhaust side communication port 33. On the other hand, each intake valve 34 and each exhaust valve 35 closes each intake side communication port 32 and each exhaust side communication port 33 by moving backward from the valve opening position to the valve closing position.

  At this time, the amount of movement of each intake valve 34 from the closed position to the open position, that is, the lift amount can be changed by the variable valve mechanism 50 (lift amount variable means). The variable valve mechanism 50 is a so-called VVT (Variable Valve Timing). The lift amount is set by the cam profile of the cam 48 provided on the intake side camshaft 40, and the variable valve mechanism 50 appropriately switches between the cam 48 that is the normal lift amount and the cam 48 that is the small lift amount. Thus, the lift amount of each intake valve 34 can be changed between the normal lift amount and the small lift amount. The lift amount changed by the variable valve mechanism 50 is varied according to the operating state of the engine 1. Specifically, when the engine 1 is operated at a low load, the amount of air taken into the combustion chamber 16 is small. Therefore, while each intake valve 34 is operated with a small lift, when the engine 1 is operated with a high load, the amount of air taken into the combustion chamber 16 increases, so that each intake valve 34 is operated with a normal lift.

  A spark plug 44 is disposed at the top of the combustion chamber 16 so that the tip protrudes, and a fuel injection valve that injects fuel into the combustion chamber 16 below the intake port 30 of the cylinder head 12. 45 (pressure raising means) is provided. In addition, although mentioned later for details, the fuel injection valve 45 is arrange | positioned so that fuel can be injected toward each intake valve 34 vicinity of the combustion chamber 16. FIG.

  Here, the combustion operation of one combustion cycle in each cylinder of the engine 1 will be described. In the combustion cycle, an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke are sequentially performed.

  In the intake stroke, the piston 13 starts moving from the top dead center to the bottom dead center, and the intake valve 34 is moved forward to open the intake side communication port 32. Then, air is sucked into the combustion chamber 16 through the intake side communication port 32 due to the negative pressure of the combustion chamber 16, and thereafter, the intake valve 34 is moved backward to close the intake side communication port 32. At this time, fuel injection is started from the fuel injection valve 45, and the sucked air and the fuel are mixed to become an air-fuel mixture.

  In the compression stroke, the piston 13 moves from the bottom dead center to the top dead center. When the piston 13 moves to the top dead center, the air-fuel mixture is compressed along with this movement. When the piston 13 reaches near the top dead center, the spark plug 44 is sparked to ignite the air-fuel mixture. The fuel injection from the fuel injection valve 45 ends before the spark plug 44 is discharged.

  In the expansion stroke, the air-fuel mixture expands (explodes) by combustion of the air-fuel mixture by ignition, and moves the piston 13 from the top dead center toward the bottom dead center.

  In the exhaust stroke, the piston 13 that has reached the bottom dead center moves again toward the top dead center due to inertia. At this time, the exhaust valve 35 is moved forward to open the exhaust side communication port 33, and the exhaust gas after combustion is discharged from the exhaust side communication port 33 as the piston 13 moves to the top dead center. After the exhaust gas is discharged, the exhaust valve 35 is moved backward to close the exhaust side communication port 33.

  By repeating the above combustion cycle, each piston 13 is moved up and down, and this power is transmitted to the crankshaft 14 via the connecting rod 15, whereby the engine 1 can obtain driving force.

  As shown in FIG. 2, when the engine 1 is operating at a low load, each intake valve 34 moves forward and backward with a small lift amount. Therefore, when each intake valve 34 is opened, The air sucked into the combustion chamber 16 through each intake valve 34 flows along the wall surface of the combustion chamber 16. In other words, if the lift amount of each intake valve 34 is a small lift amount, the opening area becomes smaller than the normal lift amount, and the flow along the wall surface of the combustion chamber 16 tends to occur. At this time, the pressure in the combustion chamber 16 in the vicinity immediately below each intake valve 34 in the forward direction is lower than the pressure on the wall surface side of the combustion chamber 16. Then, the air flowing along the wall surface of the combustion chamber 16 is attracted to the vicinity of each intake valve 34 in the combustion chamber 16 due to the pressure difference, thereby generating a plurality of small vortices (turbulent flow). If a plurality of small vortices are generated, it becomes difficult to form a tumble flow that is a mainstream. For this reason, in this embodiment, when each intake valve 34 is opened, fuel is injected from the fuel injection valve 45 into the vicinity of each intake valve 34 in the combustion chamber 16, and the pressure in the vicinity of each intake valve 34 in the combustion chamber 16. Is raised, the pressure difference in the combustion chamber 16 is reduced. As a result, the air flowing along the wall surface of the combustion chamber 16 can suitably form a tumble flow without being drawn near to the vicinity of each intake valve 34. Hereinafter, the fuel injection valve 45 which is a characteristic part of the present invention will be described.

  The fuel injection valve 45 has its fuel injection operation and fuel injection timing controlled by the engine ECU 2, and the engine ECU 2 controls the fuel injection valve 45 so that all of the fuel injected in one combustion cycle is supplied a plurality of times. It is the structure which can perform the multi-pilot injection injected separately. In the multi-pilot injection, among the total number of fuel injections in one combustion cycle, when each intake valve 34 is opened, at least one fuel injection is performed and the piston 13 is located near the bottom dead center. The remaining number of fuel injections are performed.

  The fuel injection valve 45 is disposed so as to be able to inject fuel into the combustion chamber 16 in front of each intake valve 34 in the forward direction, in other words, into the combustion chamber 16 immediately below each intake valve 34 that moves up and down. Yes. Specifically, the fuel injection valve 45 is disposed such that the injection direction for injecting fuel toward the combustion chamber 16 is a low V angle. Note that the low V angle is an angle at which a plane perpendicular to the central axis of the cylinder bore 24 is 0 ° and is inclined toward the bottom dead center to become an acute angle.

  Furthermore, the fuel injection valve 45 can change the penetration force of fuel injection. The penetrating force is changed by changing the fuel pressure (fuel pressure) of the fuel injection valve 45, the injection period of the fuel injection valve 45, the injection hole of the fuel injection valve 45, and the like. When varying the penetration force of fuel injection, for example, the engine ECU 2 controls the high-pressure pump 66 provided in the fuel supply system 60 that supplies fuel to the fuel injection valve 45, thereby supplying the fuel to the fuel injection valve 45. The pressure (fuel pressure) of the fuel is made variable, thereby changing the penetration force of the fuel injection. Specifically, the fuel supply system 60 includes a delivery passage 65 connected to the combustion injection valve 45, a variable volume high pressure pump 66 connected to the delivery passage 65, and a fuel tank 67 connected to the high pressure pump 66. And a fuel pressure sensor 68 is provided in the delivery passage 65. The fuel pressure sensor 68 and the high pressure pump 66 are connected to the engine ECU 2, and the engine ECU 2 controls the high pressure pump 66 based on the detection result of the fuel pressure sensor 67. The penetration force of fuel injection is such that when each intake valve 34 moves forward and backward with a normal lift amount, fuel is injected with a preset normal penetration force, while each intake valve 34 advances and retreats with a small lift amount. When moving, the fuel is injected with a low penetrating force that is lower than the normal penetrating force.

  Here, a series of operations for injecting fuel from the fuel injection valve 45 when each intake valve 34 moves forward and backward with a small lift amount will be described with reference to FIGS. In the intake stroke, when each intake valve 34 is moved forward to open the intake side communication port 32, air is taken into the combustion chamber 16 from each intake port 30. At this time, as shown in FIG. 3, the fuel injection valve 45 performs fuel injection with a low penetrating force toward the combustion chamber 16 in the vicinity immediately below each intake valve 34 (pressure rising injection). Specifically, as shown in FIG. 4, the fuel injection valve 45 has at least one of the total number of fuel injections in one combustion cycle in the vicinity of the maximum flow velocity of the air sucked into the combustion chamber 16. Fuel injection is performed as pressure increase injection.

  FIG. 4 is a graph showing a change in the flow velocity of the air sucked into the combustion chamber 16 in the intake stroke. In this graph, the horizontal axis represents the crank angle, and the vertical axis represents the air flow velocity. R1 is a change in the flow velocity of air when each intake valve 34 is opened at the reference valve opening timing, and R2 is each intake valve at the valve opening timing delayed from the reference valve opening timing. This is a change in the air flow rate when the valve 34 is opened. Here, when comparing R1 and R2, the maximum of the flow rate of R2 is retarded compared to the maximum of the flow rate of R1. That is, when the opening timing of each intake valve 34 is retarded, the maximum flow velocity is also retarded accordingly. This graph is stored in the engine ECU 2, and the engine ECU 2 injects fuel from the fuel injection valve 45 at a crank angle at which the flow velocity is maximum based on this graph. A plurality of graphs (two in this embodiment: R1, R2) are provided corresponding to the opening timing of each intake valve 34, and this graph is derived in advance through experiments or the like. Thereby, even if the valve opening timing of each intake valve 34 is advanced or retarded, the engine ECU 2 corresponds to the valve opening timing of each intake valve 34 advanced or retarded, and opens each intake valve 34. It is possible to perform pressure rising injection at a crank angle at which the flow velocity is maximized.

  When fuel having a low penetrating force is injected from the fuel injection valve 45, the pressure in the combustion chamber 16 in the vicinity immediately below each intake valve 34 in the forward direction increases due to the injected fuel. Then, since the pressure difference between the pressure on the wall surface side of the combustion chamber 16 through which the intake air flows and the pressure in the combustion chamber 16 in the vicinity of the position immediately below each intake valve 34 is reduced, the pressure difference along the wall surface of the combustion chamber 16 is reduced. Thus, the flowing air is not attracted to the vicinity immediately below each intake valve 34. Thereby, the air which flows along the wall surface of the combustion chamber 16 can form a tumble flow satisfactorily.

  Thereafter, when the piston 13 reaches near the bottom dead center, the fuel injection valve 45 performs the remaining number of times of fuel injection with a low penetration force (fuel injection). At this time, since the tumble flow is formed in the combustion chamber 16 by the pressure rising injection by the fuel injection valve 45, the fuel injection valve 45 can perform the fuel injection along the flow of the tumble flow. Thus, the tumble flow can be accelerated. In the vicinity of the bottom dead center of the piston 13, the fuel injection valve 45 injects the fuel with a low penetration force. However, the fuel injection valve 45 may inject the fuel with a normal penetration force.

  Next, a series of operations for injecting fuel from the fuel injection valve 45 when each intake valve 34 moves forward and backward by the normal lift amount will be described with reference to FIG. In the intake stroke, when each intake valve 34 is moved forward to open the intake side communication port 32, air is taken into the combustion chamber 16 from each intake port 30. In this case, since the lift amount of each intake valve 34 is the normal lift amount, the air sucked into the combustion chamber 16 forms a tumble flow satisfactorily as shown in FIG. For this reason, when each intake valve 34 is opened, it is not necessary to perform pressure increase injection by the fuel injection valve 45 when the flow velocity of the intake air is maximum.

  Thereafter, when the piston 13 reaches near the bottom dead center, the fuel injection valve 45 normally injects the fuel with a penetrating force. At this time, since the tumble flow is formed in the combustion chamber 16, the fuel injection valve 45 can perform fuel injection along the flow of the tumble flow, and can increase the speed of the tumble flow. Become.

  According to the above configuration, when it is difficult to form a tumble flow in the combustion chamber 16 during the intake stroke, when each intake valve 34 is opened, the combustion chamber 16 is located immediately below the forward direction of each intake valve 34. On the other hand, by injecting fuel from the fuel injection valve 45 with a low penetration force, that is, by pressure-injecting injection, the pressure in the vicinity of each intake valve 34 in the combustion chamber 16 can be increased. Therefore, the pressure difference between the pressure on the wall surface side of the combustion chamber 16 and the pressure in the vicinity of each intake valve 34 in the combustion chamber 16 can be reduced, and the air flowing along the wall surface of the combustion chamber 16 is combusted. A tumble flow can be formed satisfactorily without being drawn near the intake valves 34 in the chamber 16.

  Further, when each intake valve 34 moves forward and backward with a small lift amount, when each intake valve 34 is opened, after the pressure increase injection is performed by the fuel injection valve 45, the piston 13 reaches near the bottom dead center. The fuel injection valve 45 can accelerate the tumble flow by performing fuel injection along the flow of the formed tumble flow.

  Further, even when each intake valve 34 moves forward and backward by the normal lift amount, when the piston 13 reaches the vicinity of the bottom dead center, the fuel injection valve 45 causes the fuel injection along the flow of the tumble flow formed. By performing this, the tumble flow can be accelerated.

  In the first embodiment, the pressure increase injection and the fuel injection are performed without changing the injection angle of the fuel injection valve 45. However, in order to perform the optimal injection according to the pressure increase injection and the fuel injection, respectively. You may change an injection angle suitably. Alternatively, two fuel injection valves 45 may be prepared, one used for pressure increase injection and the other used for fuel injection. In this case, the fuel injection valve 45 used for the pressure increase injection is disposed so as to have an optimal injection angle for the pressure increase injection, and the fuel injection valve 45 used for the fuel injection has an optimal injection angle for the fuel injection. It is preferable to arrange so that.

  Next, the engine 101 according to the second embodiment will be described with reference to FIGS. 6 and 7. Only different parts will be described in order to avoid duplicate descriptions. FIG. 6 is an explanatory diagram of a tumble flow formed in the combustion chamber when the intake valve of the engine according to the second embodiment moves forward and backward with a small lift amount, and FIG. 7 illustrates the combustion chamber of the engine according to the second embodiment. FIG. The engine 101 according to the second embodiment includes a first fuel injection valve 110 and a second fuel injection valve 111. The first fuel injection valve 110 (pressure increase means) is used for pressure increase injection, and the second fuel injection valve is used. 111 is used for fuel injection. At this time, the first fuel injection valve 110 sprays fuel to the end 112 of each intake valve 34 in the forward direction by performing fuel injection with a normal penetration force when each intake valve 34 is opened. .

  As shown in FIGS. 6 and 7, in the engine 101, a first fuel injection valve 110 used for pressure rising injection is disposed below the intake port 30 of the cylinder head 12, and in the circumferential direction of the cylinder bore 24. A second fuel injection valve 111 used for fuel injection is disposed adjacent to the first fuel injection valve 110. Similar to the fuel injection valve 45 of the first embodiment, the second fuel injection valve 111 is arranged such that the injection direction for injecting fuel toward the combustion chamber 16 is a low V angle. On the other hand, the first fuel injection valve 110 is disposed so as to have an angle at which fuel sprays onto the end 112 of each intake valve 34 in the forward direction. Further, the first fuel injection valve 110 injects fuel when each intake valve 34 is opened when each intake valve 34 moves forward and backward with a small lift amount.

  Here, a series of operations for injecting fuel from the first fuel injection valve 110 and the second fuel injection valve 111 when each intake valve 34 moves forward and backward with a small lift amount will be described. In the intake stroke, when each intake valve 34 is moved forward to open the intake side communication port 32, air is taken into the combustion chamber 16 from each intake port 30. At this time, the first fuel injection valve 110 performs fuel injection with normal penetration force toward the end 112 of each intake valve 34 in the forward direction (pressure rising injection). Also in this case, as shown in FIG. 4, the fuel is injected from the first fuel injection valve 110 in the vicinity where the flow velocity of the air sucked into the combustion chamber 16 becomes maximum.

  When fuel having a normal penetrating force is injected from the first fuel injection valve 110, the injected fuel adheres to the end 112 of each intake valve 34 in the forward direction. Then, when the piston 13 heads toward the bottom dead center, the fuel adhering to each intake valve 34 is vaporized, thereby increasing the pressure in the combustion chamber 16 in the vicinity immediately below each intake valve 34 in the forward direction. Then, since the pressure difference between the pressure on the wall surface side of the combustion chamber 16 through which the intake air flows and the pressure of the combustion chamber 16 in the vicinity of each intake valve 34 is reduced, the air flowing along the wall surface of the combustion chamber 16 is It is not attracted to the vicinity immediately below each intake valve 34. Thereby, the air which flows along the wall surface of the combustion chamber 16 can form a tumble flow satisfactorily.

  Thereafter, when the piston 13 reaches the vicinity of the bottom dead center, the second fuel injection valve 111 injects the fuel with a normal penetration force. At this time, since the tumble flow is formed in the combustion chamber 16 by the pressure rising injection by the first fuel injection valve 110, the second fuel injection valve 111 performs the fuel injection along the flow of the tumble flow. As a result, the tumble flow can be accelerated.

  Next, a series of operations for injecting fuel from the first fuel injection valve 110 and the second fuel injection valve 111 when each intake valve 34 moves forward and backward by the normal lift amount will be described. In the intake stroke, when each intake valve 34 is moved forward to open the intake side communication port 32, air is taken into the combustion chamber 16 from each intake port 30. In this case, since the lift amount of each intake valve 34 is a normal lift amount, the air sucked into the combustion chamber 16 forms a tumble flow satisfactorily. For this reason, when each intake valve 34 is opened, it is not necessary to inject fuel from the first fuel injection valve 110 when the flow velocity of the intake air is maximum.

  Thereafter, when the piston 13 reaches near the bottom dead center, the second fuel injection valve 111 normally injects the fuel with a penetrating force. At this time, since the tumble flow is formed in the combustion chamber 16, the second fuel injection valve 111 can increase the tumble flow by performing fuel injection along the flow of the tumble flow. It becomes.

  Even in the above configuration, when it is difficult to form a tumble flow in the combustion chamber 16 during the intake stroke, the fuel hits the end 112 of each intake valve 34 in the forward direction when each intake valve 34 is opened. As described above, by injecting fuel from the first fuel injection valve 110, that is, by performing pressure increase injection, the pressure in the vicinity of each intake valve 34 in the combustion chamber 16 can be increased. Therefore, the pressure difference between the pressure on the wall surface side of the combustion chamber 16 and the pressure in the vicinity of each intake valve 34 in the combustion chamber 16 can be reduced, and the air flowing along the wall surface of the combustion chamber 16 is combusted. A tumble flow can be formed satisfactorily without being drawn near the intake valves 34 in the chamber 16. Further, since it is not necessary to change the penetration force of the first fuel injection valve 110 and the second fuel injection valve 111, it is not necessary to make a structure for changing the fuel pressure.

  In Example 2, the first fuel injection valve 110 and the second fuel injection valve 111 were used to perform the pressure increase injection and the fuel injection, respectively, but the single fuel injection valve was used to perform the pressure increase injection and the fuel injection. Fuel injection may be performed. In this case, it is preferable to change the injection angle of the fuel injection valve in accordance with the pressure increase injection and the fuel injection so that the optimum injection can be performed.

  Next, the engine 201 according to the third embodiment will be described with reference to FIG. Only different parts will be described in order to avoid duplicate descriptions. FIG. 8 is an explanatory diagram of the tumble flow formed in the combustion chamber when the intake valve of the engine according to the third embodiment moves forward and backward with a small lift amount. The engine 201 according to the third embodiment includes an air injection valve 202 (pressure increasing means) capable of injecting air into the combustion chamber 16 when each intake valve 34 is opened. The air injection valve 202 is an air injection valve. As a result, the pressure in the combustion chamber 16 in the vicinity of the position immediately below each intake valve 34 in the forward direction is increased.

  In this engine 201, a fuel injection valve 203 that injects fuel into the combustion chamber 16 is disposed below the intake port 30 of the cylinder head 12, and is adjacent to the fuel injection valve 203 in the circumferential direction of the cylinder bore 24. An injection valve 202 is provided. And the fuel injection valve 203 is arrange | positioned so that the injection direction which injects a fuel toward the combustion chamber 16 may become a low V angle similarly to the fuel injection valve 45 of Example 1. FIG. On the other hand, the air injection valve 202 has an air injection timing controlled by the engine ECU 2 and is disposed so as to be able to inject air into the combustion chamber 16 in the vicinity of the intake valve 34 in the forward direction. Further, the air injection valve 202 injects air when each intake valve 34 is opened when each intake valve 34 moves forward and backward with a small lift amount.

  Here, a series of operations for injecting air from the air injection valve 202 and the fuel injection valve 203 when each intake valve 34 moves forward and backward with a small lift amount will be described. In the intake stroke, when each intake valve 34 is moved forward to open the intake side communication port 32, air is taken into the combustion chamber 16 from each intake port 30. At this time, the air injection valve 202 performs air injection toward the combustion chamber 16 in the vicinity immediately below each intake valve 34 (pressure rising injection). Specifically, as shown in FIG. 4, air is injected from the air injection valve 202 in the vicinity where the flow velocity of the air sucked into the combustion chamber 16 becomes maximum.

  When air is injected from the air injection valve 202, the pressure in the combustion chamber 16 in the vicinity immediately below each intake valve 34 in the forward direction increases due to the injected air. Then, since the pressure difference between the pressure on the wall surface side of the combustion chamber 16 through which the intake air flows and the pressure of the combustion chamber 16 in the vicinity of each intake valve 34 is reduced, the air flowing along the wall surface of the combustion chamber 16 is It is not attracted to the vicinity immediately below each intake valve 34. Thereby, the air which flows along the wall surface of the combustion chamber 16 can form a tumble flow satisfactorily.

  Thereafter, when the piston 13 reaches near the bottom dead center, the fuel injection valve 203 injects the fuel with a normal penetration force. At this time, since the tumble flow is formed in the combustion chamber 16 by the pressure rising injection by the air injection valve 202, the fuel injection valve 203 performs the fuel injection along the flow of the tumble flow to thereby tumble. The flow can be increased.

  Next, a series of operations for injecting fuel from the air injection valve 202 and the fuel injection valve 203 when each intake valve 34 moves forward and backward by the normal lift amount will be described. In the intake stroke, when each intake valve 34 is moved forward to open the intake side communication port 32, air is taken into the combustion chamber 16 from each intake port 30. In this case, since the lift amount of each intake valve 34 is a normal lift amount, the air sucked into the combustion chamber 16 forms a tumble flow satisfactorily. For this reason, when each intake valve 34 is opened, it is not necessary to inject air from the air injection valve 202 when the flow velocity of the intake air is maximum.

  Thereafter, when the piston 13 reaches near the bottom dead center, the fuel injection valve 203 normally injects with a penetrating force. At this time, since the tumble flow is formed in the combustion chamber 16, the fuel injection valve 203 can increase the tumble flow by performing fuel injection along the flow of the tumble flow. .

  Even in the above configuration, when it is difficult to form a tumble flow in the combustion chamber 16 in the intake stroke, when the intake valve 34 is opened, the intake valve 34 is directed toward the combustion chamber 16 immediately below the forward direction. Thus, the pressure in the vicinity of each intake valve 34 in the combustion chamber 16 can be increased by injecting air from the air injection valve 202, that is, by performing pressure increase injection. Therefore, the pressure difference between the pressure on the wall surface side of the combustion chamber 16 and the pressure in the vicinity of each intake valve 34 in the combustion chamber 16 can be reduced, and the air flowing along the wall surface of the combustion chamber 16 is combusted. A tumble flow can be formed satisfactorily without being drawn near the intake valves 34 in the chamber 16.

  As described above, the present invention is useful for an in-cylinder direct injection internal combustion engine, and is particularly suitable for forming a tumble flow in a combustion chamber.

1 is a schematic configuration diagram of an engine according to Embodiment 1. FIG. It is explanatory drawing of the tumble flow formed in a combustion chamber, when the intake valve of the engine concerning the conventional moves forwards and backwards by small lift amount. It is explanatory drawing of the tumble flow formed in a combustion chamber when the intake valve of the engine concerning Example 1 moves forward / backward with a small lift amount. It is a graph showing the change of the flow velocity of the air suck | inhaled in a combustion chamber in an intake stroke. It is explanatory drawing of the tumble flow formed in a combustion chamber when an intake valve moves forwards and backwards by normal lift amount. It is explanatory drawing of the tumble flow formed in a combustion chamber in case the intake valve of the engine concerning Example 2 moves forward / backward with a small lift amount. It is a bottom view of the combustion chamber of the engine concerning Example 2. FIG. FIG. 10 is an explanatory diagram of a tumble flow formed in a combustion chamber when an intake valve of an engine according to a third embodiment moves forward and backward with a small lift amount.

Explanation of symbols

1 Engine (Example 1)
16 Combustion chamber 30 Intake port 32 Intake side communication port 34 Intake valve 40 Intake side camshaft 45 Fuel injection valve 50 Variable valve mechanism 66 High pressure pump 101 Engine (Example 2)
DESCRIPTION OF SYMBOLS 110 1st fuel injection valve 111 2nd fuel injection valve 112 End part of intake valve 201 Engine (Example 3)
202 Air injection valve 203 Fuel injection valve

Claims (8)

An intake valve that can advance from a valve closing position that closes the intake passage communicating with the combustion chamber to a valve opening position that opens the intake passage, and that can retract from the valve opening position to the valve closing position;
An internal combustion engine, comprising: a pressure increasing means capable of increasing the pressure of the combustion chamber in front of the intake valve in the forward direction when the intake valve is opened. A fuel injection valve capable of injecting fuel into the combustion chamber;
The internal combustion engine according to claim 1, wherein the fuel injection valve functions as the pressure increasing means.   The pressure at which the fuel injection valve injects fuel toward the combustion chamber in the forward direction of the intake valve with a low penetration force lower than a preset normal penetration force when the intake valve is opened. The internal combustion engine according to claim 2, wherein the ascending injection is performed.   The fuel injection valve performs a pressure increase injection for spraying fuel to an end portion of the intake valve in a forward direction with a normal penetration force set in advance when the intake valve is opened. 2. The internal combustion engine according to 2. Depending on the operating condition of the internal combustion engine, the lift amount of the intake valve from the closed position to the open position is between a preset normal lift amount and a small lift amount smaller than the normal lift amount. Further comprising a lift amount varying means that can be varied at
The fuel injection valve is
When the intake valve moves forward and backward by the normal lift amount, while performing fuel injection along the flow of the tumble flow formed in the combustion chamber,
5. The internal combustion engine according to claim 3, wherein the pressure increase injection is performed when the intake valve moves forward and backward by the small lift amount. The fuel injection valve is configured to be able to inject fuel into a plurality of times during one combustion cycle,
When the intake valve is opened, the fuel injection valve performs at least one fuel injection as the pressure increase injection among the total number of fuel injections in one combustion cycle, and performs the remaining number of fuel injections. The internal combustion engine according to any one of claims 3 to 5, wherein the internal combustion engine is performed along a tumble flow formed in the combustion chamber. An air injection valve capable of injecting air into the combustion chamber;
The air injection valve functions as the pressure increasing means,
The said air injection valve performs the pressure rise injection which injects air toward the said combustion chamber ahead of the advancing direction of the said intake valve at the time of the valve opening of the said intake valve. Internal combustion engine. A fuel injection valve capable of injecting fuel into the combustion chamber;
When the intake valve is opened, the air injection valve performs the pressure rising injection, and the fuel injection valve performs fuel injection along a flow of a tumble flow formed in the combustion chamber. The internal combustion engine according to claim 7.

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