JP2009085012A - Internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an internal combustion engine capable of improving homogeneity of air fuel mixture by strengthening a tumble flow inside a cylinder. <P>SOLUTION: The internal combustion engine is a cylinder direct injection type internal combustion engine having a piston and the cylinder storing the piston so as to enable reciprocation and dividing predetermined amount of fuel to directly inject the divided fuel to inside of the cylinder a plurality of times. In this internal combustion engine, an intersection point P between an extension in the fuel injection direction and a wall face of the cylinder is positioned on the upper side from the bottom dead center of the piston, in cross sectional view in the axial direction of the cylinder. When main fuel injection which is primary injection and sub fuel injection performed subsequent to the main fuel injection are performed, before the top face of the piston passes through the intersection point P during the compression stroke of the engine, the sub fuel injection is performed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an internal combustion engine, and more particularly to an internal combustion engine that can improve the homogeneity of an air-fuel mixture by strengthening a tumble flow in a cylinder.

  In recent internal combustion engines, in order to improve engine performance such as knock characteristics, a fuel injection method is employed in which a predetermined amount of fuel is divided into a plurality of times and directly injected into the cylinder.

  As a conventional internal combustion engine employing such a configuration, a technique described in Patent Document 1 is known. In a conventional internal combustion engine (cylinder injection type engine), an injector is disposed so as to inject fuel directly into a combustion chamber, and in an operating region where fuel is injected from the injector early in an intake stroke to perform uniform combustion. In a direct injection engine in which a certain uniform combustion region is set, the intake air flow rate detection means, the pre-injection time before the early injection start time in the uniform combustion region, and the post-injection after the early injection start time A filling amount calculating means for calculating the intake filling amount based on the detected intake air flow rate at both the time point and determining the fuel injection amount in the early injection based on the intake filling amount calculated at the time point before the injection, When the intake charge amount calculated at the post-injection time is larger than the intake charge amount calculated at the pre-injection time, an amount of fuel corresponding to the increase is injected during the first half of the compression stroke Characterized by comprising a fuel control means for causing the morphism.

JP 11-36958 A

  Here, in a direct injection type internal combustion engine in which fuel is directly injected into a cylinder, there is a problem that a tumble flow (intake flow) is effectively formed in the cylinder to improve the homogeneity of the air-fuel mixture. Such homogenization of the air-fuel mixture improves engine performance such as knock characteristics.

  Accordingly, the present invention has been made in view of the above, and an object thereof is to provide an internal combustion engine that can improve the homogeneity of the air-fuel mixture by strengthening the tumble flow in the cylinder.

  In order to achieve the above object, an internal combustion engine according to the present invention has a piston and a cylinder that reciprocally accommodates the piston, and a cylinder that divides a predetermined amount of fuel into multiple times and directly injects the fuel into the cylinder. An internal direct injection internal combustion engine, wherein an intersection P between an extension line in the fuel injection direction and a wall surface of the cylinder is above the bottom dead center of the piston in an axial sectional view of the cylinder, and When the main fuel injection that is the main fuel injection and the sub fuel injection performed after the main fuel injection are performed, before the top surface of the piston passes the intersection P during the compression stroke of the engine The sub fuel injection is performed.

  In this internal combustion engine, before the top surface of the piston passes a predetermined intersection P during the compression stroke of the engine, sub fuel injection is performed supplementarily to strengthen the tumble flow R in the cylinder. In such a configuration, (1) compared with a configuration in which only main fuel injection is performed, the tumble flow is effectively enhanced and the homogeneity of the air-fuel mixture is improved. Thereby, there is an advantage that the combustion speed of the fuel is increased and the knock characteristics of the engine are improved. Further, (2) there is an advantage that the tumble flow is effectively enhanced as compared with the configuration in which the sub fuel injection is performed after the top surface of the piston passes the predetermined intersection P.

  In the internal combustion engine according to the present invention, the crank angle a when the top surface of the piston is at the intersection P and the crank angle b when the sub fuel injection is performed are a-30 [deg] ≦ b ≦. It has a relationship of a-10 [deg].

  In this internal combustion engine, sub fuel injection is performed at a crank angle b that is 10 [deg] to 30 [deg] before the crank angle a when the top surface of the piston is at the intersection P. Such a configuration has an advantage that the tumble flow R is effectively strengthened because the sub fuel injection timing (crank angle b) is optimized.

  In the internal combustion engine according to the present invention, when the predetermined amount of fuel is divided and injected three times or more, the sub fuel injection is performed last.

  In this internal combustion engine, after the sub fuel injection is performed before the top surface of the piston passes the intersection P during the compression stroke of the engine, the fuel injection is not performed. This has the advantage that the tumble flow is effectively enhanced.

  In the internal combustion engine according to the present invention, the main fuel injection is performed when the piston is in the vicinity of bottom dead center during the intake stroke of the engine.

  In this internal combustion engine, main fuel injection is performed when the cylinder volume is sufficiently large. Thereby, a tumble flow is efficiently formed in the cylinder, and the homogeneity of the air-fuel mixture is improved.

  In the internal combustion engine according to the present invention, during the compression stroke of the engine and before the top surface of the piston passes the predetermined intersection P, the sub fuel injection is performed auxiliary to strengthen the tumble flow R in the cylinder. The In such a configuration, (1) compared with a configuration in which only main fuel injection is performed, the tumble flow is effectively enhanced and the homogeneity of the air-fuel mixture is improved. Thereby, there is an advantage that the combustion speed of the fuel is increased and the knock characteristics of the engine are improved. Further, (2) there is an advantage that the tumble flow is effectively enhanced as compared with the configuration in which the sub fuel injection is performed after the top surface of the piston passes the predetermined intersection P.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. Further, the constituent elements of this embodiment include those that can be replaced while maintaining the identity of the invention and that are obvious for replacement. In addition, a plurality of modifications described in this embodiment can be arbitrarily combined within a range obvious to those skilled in the art.

[Internal combustion engine]
FIG. 1 is a block diagram showing an internal combustion engine according to an embodiment of the present invention. 2-6 is explanatory drawing which shows the effect | action of the internal combustion engine described in FIG. The internal combustion engine 1 is applied to, for example, an in-cylinder injection type four-cycle gasoline engine (see FIG. 1). The internal combustion engine 1 includes an engine 2, an intake system 3, an exhaust system 4, and a control system 5.

  The engine 2 includes a piston 21, a cylinder (cylinder bore) 22 that accommodates the piston 21, a crankshaft 23 that is coupled to the piston 21, an intake port 24 and an exhaust port 25 that are connected to the cylinder 22, and fuel injection. It has an injector 26 and a spark plug 27. In the engine 2, the cross-section P of the cylinder 22 is located above the bottom dead center TDC of the piston 21 so that the intersection P between the extension line in the fuel injection direction and the wall surface of the cylinder 22 is above the bottom dead center TDC of the piston 21. An injector 26 is installed. In the engine 2, air is sucked into the cylinder 22 from the intake port 24 and compressed, and fuel is injected from the injector 26 into the cylinder 22 to form an air-fuel mixture. The air-fuel mixture is ignited by the spark plug 27 and burned in the cylinder 22 (combustion chamber), and the piston 21 is driven by the combustion energy to reciprocate in the cylinder 22. Then, the reciprocating motion of the piston 21 is converted into the rotational motion of the crankshaft 23 to generate power. Further, the combustion gas in the cylinder 22 is discharged to the outside of the cylinder 22 through the exhaust port 25.

  The intake system 3 includes an intake passage (intake pipe) 31 and an air filter 32, a throttle valve 33, and a surge tank 34 disposed on the intake passage 31. The intake passage 31 is connected to the intake port 24 of the engine 2 via an intake manifold. The air filter 32 is a filter that is disposed at the inlet of the intake passage 31 and removes dust, dust, and the like in the intake air. The throttle valve 33 is a flow rate adjusting valve that adjusts the cross-sectional area of air in the intake passage 31. The surge tank 34 is a tank that temporarily stores intake air and suppresses intake pulsation. In the intake system 3, the intake air that has passed through the air filter 32 is introduced into the engine 2 through the intake passage 31.

  The exhaust system 4 includes an exhaust passage (exhaust pipe) 41, and a first catalyst device 42 and a second catalyst device 43 disposed on the exhaust passage 41. The exhaust passage 41 is connected to the exhaust port 25 of the engine 2 via an exhaust manifold. The first catalyst device 42 and the second catalyst device 43 have a function of purifying the exhaust gas flowing through the exhaust passage 41. In the exhaust system 4, the exhaust of the engine 2 passes through the exhaust passage 41 and is purified by the catalyst devices 42 and 43 and discharged.

  The control system 5 includes an ECU (Electronic Control Unit) 51, a rotation speed sensor 52 that measures the rotation speed of the engine 2, and a torque sensor (not shown) that measures the load of the engine 2. In the control system 5, the ECU 51 performs fuel injection control, which will be described later, based on output signals from various sensors 52.

[Fuel injection control]
In the internal combustion engine 1, in order to improve engine performance, a predetermined amount of fuel is divided into a plurality of times (two or more times) and directly injected into the cylinder 22 (see FIGS. 1 and 2). For example, in this embodiment, fuel injection control is performed as follows.

  First, in the intake stroke of the engine 2, a tumble flow (intake flow) R is formed in the cylinder 22 by the intake air introduced from the intake port 24 (see FIG. 3). This tumble flow R flows from the intake port 24 side to the exhaust port 25 side in the combustion chamber (forward tumble flow).

  Next, when the piston 21 is at the bottom dead center BDC in this intake stroke, main fuel injection, which is the main fuel injection, is performed (see FIGS. 2 and 3). At this time, the fuel is injected along the tumble flow R in the cylinder 22 and is injected in a direction that strengthens the tumble flow R. Thereby, the homogeneity of the air-fuel mixture is improved.

  Next, after the main fuel injection, sub fuel injection, which is auxiliary fuel injection, is performed (see FIGS. 2 and 4). This sub fuel injection is in the compression stroke of the engine 2 and the top surface of the piston 21 passes through a predetermined point P (intersection of the extension line in the fuel injection direction and the wall surface of the cylinder 22; see FIG. 5). Performed before (immediately before). Specifically, when the piston 21 rises from the bottom dead center BDC and a compression stroke is performed, sub fuel injection is performed in a section between the bottom dead center BDC and a predetermined point P. This sub fuel injection is mainly performed to strengthen (increase the speed) the tumble flow R formed in the cylinder 22. That is, the tumble flow R in the cylinder 22 is attenuated with the passage of time from immediately after its formation. For this reason, sub fuel injection is performed during the compression stroke of the engine 2 and the tumble flow R is strengthened. Thereby, the homogeneity of the air-fuel mixture is further improved.

[effect]
As described above, in the internal combustion engine 1, the sub fuel injection is performed auxiliary to the inside of the cylinder 22 during the compression stroke of the engine 2 and before the top surface of the piston 21 passes the predetermined intersection point P. The tumble flow R is strengthened. In such a configuration, (1) compared to a configuration in which only main fuel injection is performed, the tumble flow R is effectively enhanced and the homogeneity of the air-fuel mixture is improved. Thereby, there is an advantage that the combustion speed of the fuel is increased and the knock characteristics of the engine are improved. Further, (2) there is an advantage that the tumble flow R is effectively enhanced as compared with the configuration in which the sub fuel injection is performed after the top surface of the piston 21 passes the predetermined intersection P. For example, in the configuration in which the sub fuel injection is performed when the top surface of the piston 21 is at the position of the intersection point P, the injected fuel stays in the vicinity of the intersection point P, and the speed-up effect of the tumble flow R decreases. Further, in the configuration in which the sub fuel injection is performed after the top surface of the piston 21 passes the intersection P, the injected fuel may hit the top surface of the piston 21 and attenuate the tumble flow R.

[Additional matters]
In the internal combustion engine 1, the crank angle a when the top surface of the piston 21 is at the intersection point P and the crank angle b when the sub fuel injection is performed are a-30 [deg] ≦ b ≦ a-10. [Deg] is preferable (see FIG. 2). That is, sub fuel injection is performed at a crank angle b that is 10 [deg] to 30 [deg] before the crank angle a when the top surface of the piston 21 is at the intersection P. Such a configuration has an advantage that the tumble flow R is effectively enhanced because the sub fuel injection timing (crank angle b) is optimized. For example, when b <a-30 [deg], the sub fuel injection timing is too early, and the tumble flow R may be attenuated between the sub injection and the ignition timing. Further, when a-10 [deg] <b (<a), the injected fuel tends to stay near the intersection P, and the speed-up effect of the tumble flow R may be reduced.

  In the above configuration, the crank angle b of the sub fuel injection is appropriately changed within the above range (a-30 [deg] ≦ b ≦ a−10 [deg]) in relation to the effect of increasing the tumble flow. Preferably, see FIG. Specifically, sub fuel injection is performed at a crank angle b where the tumble acceleration effect reaches its peak. Thereby, the tumble flow R is effectively strengthened. The crank angle b of the sub fuel injection can be appropriately selected according to the engine specifications and the like.

  Further, in the internal combustion engine 1, it is preferable that the sub fuel injection is performed last when a predetermined amount of fuel is divided and injected three times or more. That is, it is preferable that the fuel injection is not performed after the sub fuel injection is performed before the top surface of the piston 21 passes the intersection P during the compression stroke of the engine. Thereby, there is an advantage that the tumble flow R is effectively strengthened. For example, if fuel injection is performed after the top surface of the piston 21 passes through the intersection P, the injected fuel may strike the top surface of the piston 21 and attenuate the tumble flow R.

  In the internal combustion engine 1, the main fuel injection is preferably performed when the piston 21 is in the vicinity of the bottom dead center BDC in the intake stroke of the engine 2 (see FIGS. 2 and 3). In such a configuration, main fuel injection is performed when the cylinder volume is sufficiently large. Thereby, the tumble flow R is efficiently formed in the cylinder 22 and the homogeneity of the air-fuel mixture is improved. However, the main fuel injection timing is not particularly limited as long as it is before the sub fuel injection timing.

  In this embodiment, only the main fuel injection and the sub fuel injection are performed as described above (see FIG. 2). The main fuel injection is performed when the intake stroke of the engine 2 and the piston 21 is at the bottom dead center BDC, and the sub fuel injection is performed at a predetermined crank angle b (a-30 [deg] ≦ b ≦ a −10 [deg]).

  As described above, the internal combustion engine according to the present invention is useful in that the homogeneity of the air-fuel mixture can be improved by strengthening the tumble flow in the cylinder.

1 is a configuration diagram illustrating an internal combustion engine according to an embodiment of the present invention. It is explanatory drawing which shows the effect | action of the internal combustion engine described in FIG. It is explanatory drawing which shows the effect | action of the internal combustion engine described in FIG. It is explanatory drawing which shows the effect | action of the internal combustion engine described in FIG. It is explanatory drawing which shows the effect | action of the internal combustion engine described in FIG. It is explanatory drawing which shows the effect | action of the internal combustion engine described in FIG.

Explanation of symbols

1 Internal combustion engine 2 Engine 21 Piston 22 Cylinder 23 Crankshaft 24 Intake port 25 Exhaust port 26 Injector 27 Spark plug 3 Intake system 31 Intake passage 32 Air filter 33 Throttle valve 34 Surge tank 4 Exhaust system 41 Exhaust passage 42 First catalyst device 43 Second catalyst device 5 Control system 51 ECU
52 Speed sensor

Claims (4)

A direct injection type internal combustion engine that has a piston and a cylinder that reciprocally accommodates the piston, and divides a predetermined amount of fuel into a plurality of times and directly injects the fuel into the cylinder;
An intersection P between the extension line in the fuel injection direction and the wall surface of the cylinder is above the bottom dead center of the piston in the axial sectional view of the cylinder; and
When the main fuel injection that is the main fuel injection and the sub fuel injection performed after the main fuel injection are performed, before the top surface of the piston passes the intersection P during the compression stroke of the engine, An internal combustion engine in which the sub fuel injection is performed.   The crank angle a when the top surface of the piston is at the intersection point P and the crank angle b when the sub fuel injection is performed have a relationship of a−30 [deg] ≦ b ≦ a−10 [deg]. The internal combustion engine according to claim 1.   The internal combustion engine according to claim 1 or 2, wherein the sub fuel injection is performed last when a predetermined amount of fuel is divided and injected three times or more.   The internal combustion engine according to any one of claims 1 to 3, wherein the main fuel injection is performed when the piston is in the vicinity of bottom dead center during an intake stroke of the engine.

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