JP2013019404A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an in-cylinder injection internal combustion engine for forming homogeneous mixture gas in a cylinder suitably using tumble flow.SOLUTION: In the in-cylinder injection internal combustion engine, tumble flow is generated in a cylinder in the internal combustion engine in a prescribed time of a suction stroke, wherein a vortex center angle is defined as an angle made by a virtual vortex center line for forming by connecting a vortex center of assumed the tumble flow and a jetting port of a fuel injection device, and a reference surface extended to the radial direction of the cylinder, and an injection angle is defined as an angle made by a center line in the expansion of fuel spray injected from the fuel injection device to the longitudinal direction of the cylinder and the reference surface. Moreover, fuel injection is performed on the lower side than the reference surface in the cylinder by the fuel injection device and the ratio of the injection angle to the vortex center angle is set to ≤0.7.

Description

  The present invention relates to an internal combustion engine.

  In-cylinder direct-injection internal combustion engines that form a homogeneous mixture of fuel and intake air and perform combustion have been developed to improve fuel efficiency and reduce emissions. In such an in-cylinder direct injection type internal combustion engine, the injected fuel spray interferes with the intake valve, and fuel adheres to the intake valve, so that the required amount of fuel combustion cannot be performed and the engine output decreases. May end up. Therefore, by determining the fuel injection direction so that the central axis of the fuel spray from the fuel injection device overlaps the vertical plane passing between the two intake valves provided in the internal combustion engine, the fuel adheres to the intake valve. A technique for avoiding this is disclosed (for example, see Patent Document 1). The technique further discloses that the atomization is promoted by causing the fuel spray to collide with the tumble flow (vertical vortex flow) generated in the intake stroke to homogenize the air-fuel mixture in the cylinder. .

  Further, when a tumble flow is appropriately generated in an in-cylinder direct injection internal combustion engine, homogenization of the air-fuel mixture can be further promoted. Therefore, a technique for synchronizing an appropriate tumble flow and fuel spray even when the inflow direction of the intake air into the cylinder changes is disclosed (see, for example, Patent Document 2). In this technique, the fuel injection direction from the fuel injection device is configured to be variable, and the fuel injection direction is controlled along the intake air inflow direction.

JP 2004-218603 A JP 2008-255833 A

  In a direct injection type internal combustion engine, a tumble flow is conventionally used to homogenize the air-fuel mixture, but fuel spray is injected in the direction that collides with the tumble flow generated in the cylinder. When injected from the apparatus, the tumble flow is attenuated and the fuel does not diffuse uniformly in the cylinder, and the combustion timing comes in an unevenly distributed state. As a result, it becomes difficult to achieve fuel efficiency improvement and low emission by homogenizing the air-fuel mixture.

  Generally, in a direct injection type internal combustion engine, a fuel injection device is installed on the intake port side. In this case, the injected fuel spray may interfere with the intake valve. If fuel adheres to the intake valve, the required amount of fuel is not supplied into the cylinder, which may cause a reduction in engine output, a reduction in cooling effect due to the heat of vaporization of fuel, a deterioration in emissions, and the like.

  The present invention has been made in view of the above-described problems, and provides an in-cylinder direct injection internal combustion engine that suitably uses a tumble flow to form a homogeneous mixture in the cylinder. The purpose is to do.

In the present invention, in order to solve the above problems, the direction of the fuel spray injected from the fuel injection device reaches a position above the center of the tumble flow vortex generated in the cylinder by a predetermined ratio. The direction was decided. By adopting this configuration, it is possible to avoid the injected fuel from colliding with the tumble flow, and it is possible to achieve homogenization of the air-fuel mixture without attenuating the tumble flow by effectively synchronizing.

  More specifically, the present invention relates to a fuel injection device that is provided in the vicinity of an intake valve and directly injects fuel into the cylinder, and a tumble flow that generates a tumble flow in the longitudinal direction in the cylinder by opening and closing the intake valve. And a generation mechanism. In the internal combustion engine, the tumble flow generated in the cylinder by the tumble flow generation mechanism at a predetermined timing of the intake stroke is formed by connecting the assumed vortex center of the tumble flow and the injection port of the fuel injection device. The angle formed by the virtual vortex center line and the predetermined radial surface extending in the radial direction of the cylinder is defined as the vortex center angle, and the spread of the fuel spray injected from the fuel injection device in the longitudinal direction of the cylinder The angle formed by the center line and the predetermined radial direction surface is defined as the injection angle. The fuel injection device injects fuel below the predetermined radial surface in the cylinder, and a ratio of the injection angle to the vortex center angle is set to 0.7 or less.

  An internal combustion engine according to the present invention is a direct injection type internal combustion engine in which fuel is directly injected into a cylinder from a fuel injection device. The internal combustion engine is provided with a tumble flow generation mechanism, which can generate a tumble flow in the cylinder at a predetermined timing of the intake stroke. For the generation of the tumble flow by the tumble flow generation mechanism, various known generation modes can be adopted.For example, the shape of the intake port connected to the cylinder can be devised, or the flow of intake air drawn into the cylinder can be adjusted. By doing so, it is known that a tumble flow can be generated. Here, the tumble flow generated in the cylinder descends the cylinder inner wall on the exhaust valve side, and forms a so-called vertical vortex that rises through the piston top and the cylinder inner wall on the intake valve side. The fuel spray from the fuel injection device is synchronized with the tumble flow, so that the fuel can be efficiently diffused into the cylinder to form a homogeneous air-fuel mixture. However, if the fuel is injected in a direction opposite to the tumble flow, the momentum of the tumble flow is attenuated, and the formation of a homogeneous air-fuel mixture in the cylinder is hindered, resulting in fuel consumption deterioration and emissions. There is concern about the deterioration.

  Therefore, in the internal combustion engine according to the present invention, when the vortex center angle and the injection angle are defined as described above, the injection angle ratio that is the ratio of the injection angle to the vortex center angle is set to 0.7 or less. The vortex center angle refers to the virtual vortex center line formed by the tumble flow generated in the cylinder by the tumble flow generation mechanism and the vortex center line formed across the injection port of the fuel injection device, and the cylinder radial direction reference It is defined as the angle that the surface makes. Actually, the tumble flow generated in the cylinder is not a complete vertical vortex, but it contains irregular or regular turbulence depending on the shape of the top of the cylinder and piston, the intake velocity and direction of intake. is there. Based on this point, the tumbling center of the tumble flow assumed in the present invention is recognized as the center of the vortex flow when a person skilled in the art can grasp the tumbling flow of the tumble flow in the cylinder using a known technique. Says the position. The center of the eddy current may be recognized by a person skilled in the art, and when the eddy current is calculated using a computer such as a computer, parameters relating to the calculated eddy current (correlation between position and flow velocity, etc.) are considered. May be performed. Specifically, the calculation method based on computational fluid dynamics (CFD) using a computer etc. and other existing visualization techniques can be used to visually or numerically grasp the tumble flow in the cylinder. Then, the center of the vortex that is derived may be the vortex center of the assumed tumble flow. Therefore, the vortex center of the tumble flow to be assumed is not necessarily limited to being a singular vortex center in a strict sense, and includes a vortex center that is reasonably calculated by a person skilled in the art according to a known technique. .

On the other hand, the injection angle is defined as an angle formed by the center line of the fuel spray from the fuel injection device and the reference plane. The injection angle ratio, which is the ratio of the injection angle to the vortex center angle, means that in the range of 0 to 1, the fuel spray exists closer to the vortex center of the tumble flow as the value approaches 1. To do. However, in general, the fuel spray has a thickness in the longitudinal direction (cylinder axial direction). For example, when the fuel spray injected from the fuel injection device is a spray having a fan-shaped fan shape. It will have a relatively large thickness. For this reason, the lower side of the fuel spray is closer to the vortex center of the tumble flow than its central axis, and in some cases, it is located further below the virtual vortex center line passing through the vortex center in the cylinder. become. On the other hand, since the direction of the tumble flow is reversed above and below the virtual vortex center line, if the lower side of the fuel spray is positioned below the virtual vortex center line as described above, the fuel Since a part of the spray is injected so as to face the tumble flow, the tumble flow is attenuated, resulting in the formation of a homogeneous air-fuel mixture. Moreover, even if the virtual vortex center line is not exceeded, if the fuel spray exists only near the vortex center of the tumble flow, the speed of the tumble flow near the vortex center is lower than that of the outer peripheral portion, so that the fuel spray is effectively performed. It becomes difficult to synchronize with the tumble flow.

  Therefore, in the internal combustion engine according to the present application, the fuel injection from the fuel injection device is set below the reference plane, that is, to the vortex center side of the tumble flow, and the injection angle ratio is set to 0.7 or less. Is done. By setting the injection angle ratio to 0.7 or less, it becomes possible to synchronize the entire fuel, including the lower part of the sprayed fuel, so that attenuation of the tumble flow can be avoided, resulting in a decrease in engine output, etc. Can be suppressed. If the injection angle ratio is extremely small, the amount of fuel spray adhering to the inner wall of the cylinder may increase depending on the size of the cylinder, the fuel injection pressure, and the like. Therefore, the injection direction of the fuel injection device is preferably set so that the injection angle ratio is preferably close to 0.7.

  From the viewpoint of forming a homogeneous air-fuel mixture in the cylinder, a relatively large tumble flow is generated, and after the tumble flow and fuel spray are synchronized, the mixing of fuel and intake air is promoted by the disturbance of the tumble flow in the compression stroke. The fuel injection is preferably performed at a time in the vicinity of the intake bottom dead center in the intake stroke of the internal combustion engine. Therefore, the predetermined timing in the internal combustion engine may be a timing in the vicinity of the intake bottom dead center in the intake stroke of the internal combustion engine, whereby the injection angle ratio is 0 in the timing in the vicinity of the intake bottom dead center. It is preferable that the injection direction by the fuel injection device is set so as to be .7 or less.

  In the internal combustion engine, when the fuel spray has a fan-shaped fan shape, the fuel spray injected from the fuel injection device when the intake valve is in the maximum lift state for opening the valve is the intake valve. If there is interference, the spray width interfered by the intake valve when there is interference with the intake valve with respect to the spray width of the fuel spray when there is virtually no interference with the intake valve It is preferred that the spray interference ratio, defined as the ratio, is 0.7 or less. If the injection angle ratio is 0.7 or less, there is a possibility that the intake valve located near the fuel injection device and the fuel spray interfere with each other. If fuel adheres to the intake valve or its vicinity due to interference, there is a concern that the engine output will decrease or the emission will deteriorate. Therefore, by setting the injection angle ratio to 0.7 or less as described above and further reducing the spray interference ratio to 0.7 or less, formation of a homogeneous air-fuel mixture and avoidance of fuel adhesion to the intake valve, etc. Can be compatible.

  The internal combustion engine up to the above may be a spark ignition internal combustion engine or a compression ignition internal combustion engine as long as it is an in-cylinder direct injection internal combustion engine. For example, in the case of a spark-ignition internal combustion engine, the fuel spray injected from the fuel injection device may be homogenized in the cylinder and burned by igniting with an ignition plug. In the case of a compression ignition internal combustion engine, the premixed gas is formed homogeneously in the cylinder, and combustion is performed using the injected fuel near the compression top dead center as a fire type. In any form of internal combustion engine, in order to form a homogenized mixture (premixed mixture) in the cylinder, it can be said that it is preferable to set the injection angle ratio to 0.7 or less as described above. .

  It is possible to provide an in-cylinder direct injection internal combustion engine that suitably uses a tumble flow and forms a more homogeneous mixture in the cylinder.

1 is a diagram showing a schematic configuration of an internal combustion engine according to an embodiment of the present invention. It is a figure which shows the mode of the fuel spray in the cylinder of the internal combustion engine shown in FIG. FIG. 2 is a diagram showing a correlation between an injection angle ratio and a carbon monoxide concentration in exhaust gas in the internal combustion engine shown in FIG. 1. It is a figure which shows the condition of the spreading | diffusion of the fuel spray in the cylinder of the internal combustion engine shown in FIG. It is a figure which shows the condition of the spreading | diffusion of the fuel spray in the cylinder of the conventional internal combustion engine. FIG. 2 is a diagram showing a correlation between a stroke / bore ratio, a vortex center angle, and an injection angle in the internal combustion engine shown in FIG. 1. FIG. 2 is a diagram showing a correlation between an injection start timing and the number of PM particles contained in exhaust in the internal combustion engine shown in FIG. 1. FIG. 2 is a view showing a state of interference between fuel spray and an intake valve in the internal combustion engine shown in FIG. 1. FIG. 2 is a diagram comparing the internal combustion engine shown in FIG. 1 and a conventional port injection internal combustion engine with respect to an increase in volumetric efficiency of the cylinder and an improvement in torque exhibited by the internal combustion engine.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. The dimensions, materials, shapes, relative arrangements, and the like of the components described in the present embodiment are not intended to limit the technical scope of the invention to those unless otherwise specified.

<Example>
An embodiment of an internal combustion engine according to the present invention will be described based on the drawings attached to the present specification. FIG. 1 is a view showing a schematic configuration of a longitudinal section of an internal combustion engine according to the present embodiment, particularly in the vicinity of a fuel injection device. The internal combustion engine 1 is a cylinder ignition type spark ignition internal combustion engine for driving a vehicle. In the internal combustion engine 1, an intake port 2 and an exhaust port 3 are connected to the cylinder 8. The intake port 2 sends intake air into the cylinder 8 through opening and closing of the intake valve 3, and the exhaust port 3 sends combustion gas and the like as exhaust to the exhaust system of the internal combustion engine 1 through opening and closing of the exhaust valve 5. Although only one intake valve 4 and one exhaust valve 5 are shown in the cross-sectional view shown in FIG. 1, in reality, two intake valves 4 and two exhaust valves 5 are provided in parallel. A piston 10 is disposed in the cylinder 8, and a spark plug 6 is disposed on the top of the cylinder 8 facing the piston 10 so that the air-fuel mixture in the cylinder can be ignited.

  Further, in the internal combustion engine 1, the fuel injection device 7 is located between the two intake valves 4 below the intake port 2 (that is, closer to the cylinder block side in the cylinder head provided with the intake port 2). It is provided at the position. The injection direction of the fuel injection device 7 is generally set obliquely downward within the cylinder 8. Details of this fuel injection direction will be described later. Further, the fuel spray 7a injected from the fuel injection device 7 has a fan-shaped fan shape as shown in FIG. 7B described later, and has a certain thickness in the vertical direction as shown in FIG. The thickness of the fuel spray increases as it goes to the tip of the fuel spray.

In addition, the intake port 2 of the internal combustion engine 1 is lowered along the exhaust port 3 side of the inner wall of the cylinder 8 by the intake air introduced into the cylinder 8 during the intake stroke, that is, on the intake port 2 side of the inner wall of the cylinder 8, that is, A tumble flow generating mechanism that generates a tumble flow 9 that is a vertical vortex rising along the fuel injection device 7 side is constituted by a partition wall 11a and a shut-off valve 11b. The partition wall 11a divides the intake port 2 in the vicinity of the intake valve 4 vertically into two along the extending direction, and a closing valve 11b is provided in the lower intake port portion of the divided intake ports. The shut-off valve 11b can block the flow of the lower intake port portion and weaken the flow in accordance with an instruction from a control device such as an ECU (not shown). Thus, if the flow of the intake air in the lower intake port portion is weakened or closed by the closing valve 11b, the momentum of the intake air supplied into the cylinder 8 from the upper intake port portion where the closing valve 11b is not provided is strong. Become. As a result, the intake air is supplied into the cylinder along the upper wall of the intake port 2, and an effective tumble flow 9 can be generated in the cylinder 8. When a large amount of intake air is required, such as when a larger engine output is required in the internal combustion engine 1, the closing valve 11b is opened, and the intake air is supplied to the upper intake port portion and the lower intake port portion. It is also required to supply from both sides into the cylinder to eliminate the shortage of intake air.

  By generating a tumble flow in the cylinder 8 in this way, it becomes possible to efficiently mix the fuel spray 7a injected from the fuel injection device 7 with the intake air to form a homogeneous air-fuel mixture. In order to promote the formation of this air-fuel mixture, it is not preferable that the tumble flow attenuates in the cylinder 8. Therefore, in order to reduce the passage resistance when the tumble flow 9 travels along the top surface of the piston 10, the top of the piston 10 has an arc shape in the circumferential direction of the tumble flow as shown in FIG. A cavity having an arcuate bottom wall is formed. As described above, since the intake valve 4 is provided in the internal combustion engine 1, the two tumble flows generated in parallel in the cylinder via the two intake valves 4 are merged with each other. The width of the cavity is sufficiently large in order to turn in the cylinder and suppress attenuation at this time.

  Here, when a homogeneous air-fuel mixture is formed using the tumble flow, it is not preferable that the tumble flow is attenuated by the fuel spray 7 a injected from the fuel injection device 7. As shown in FIG. 1, the tumble flow flows along the cylinder inner wall on the exhaust valve 5 side along the lower side in the cylinder 8 and flows along the cylinder inner wall on the intake valve 4 side along the upper side. The air-fuel mixture is widely formed inside the cylinder 2 in a homogeneous state. If the flow of the tumble flow is attenuated by the fuel spray 7a, the air-fuel mixture is unevenly distributed in the cylinder 2 and a homogeneous diffusion state cannot be formed, and there is a concern about deterioration of fuel consumption and emission. Therefore, in the internal combustion engine 1 according to the present invention, the fuel injection direction from the fuel injection device 7 is determined based on the correlation between the tumble flow formed in the cylinder 2 and the fuel spray.

  The details of the fuel injection direction of the fuel injection device 7 will be described based on the longitudinal sectional view of FIG. FIG. 2 is a longitudinal sectional view of the internal combustion engine 1 as in FIG. 1, and particularly a diagram schematically showing the correlation between the fuel spray 7 a from the fuel injection device 7 and the tumble flow 9 generated in the cylinder 8. It is. First, in FIG. 2, a plane extending in the radial direction of the cylinder 8 through the injection port of the fuel injection device 7 is represented by a reference plane L0. When the cylinder 8 is installed vertically, the reference plane L0 is a horizontal plane, but when the cylinder 8 is installed obliquely in the internal combustion engine 1, it extends in a direction perpendicular to the axial direction of the cylinder 8. It becomes a surface.

Next, regarding the tumble flow 9 formed in the cylinder 2, the assumed vortex center of the tumble flow is P1, and a line connecting the injection port of the fuel injection device 7 and the vortex center P1 is a virtual vortex center line L1. And The “assumed vortex center” here includes the vortex center of the tumble flow 9 actually generated in the cylinder 8 and is based on computational fluid dynamics (CFD) using a computer or the like in advance. This includes the vortex center calculated and assumed, and the vortex center assumed for the tumble flow generated in the cylinder 8 using other existing visualization techniques. That is, the “assumed vortex center” according to the present application can be assumed by those skilled in the art in consideration of the fact that the exact vortex center of the tumble flow 9 generated in the cylinder 8 is not always stable. Says the vortex center of tumble flow in various ranges. In addition, regarding the tumble flow that is the target of the “supposed vortex center”, the tumble flow is generated in the cylinder 8 by opening the intake valve 4 and lowering the piston 10 in the intake stroke. In consideration of the mixing of the fuel spray from the device 7 and the intake air, the tumble flow generated in the cylinder 8 at a predetermined time near the intake bottom dead center in the intake stroke is set as a tumble flow that contributes to the mixing. Is preferred. For example, an assumed vortex center of the tumble flow 9 generated in the cylinder 8 when the crank angle in the internal combustion engine 1 is 220 to 180 BTDC is represented as a point P1.

  Next, as described above, the fuel spray 7a from the fuel injection device 7 has a fan shape that spreads forward. As shown in FIG. 2, the center axis passing through the center in the thickness direction (longitudinal direction) of the fuel spray 7a is defined as a spray center line L2. Therefore, when the fuel spray 7a has the spray angle C in the thickness direction, the spray center line L2 equally divides the spray angle C.

  When the reference plane L0, the virtual vortex center line L1, and the spray center line L2 are set in this way, the internal combustion engine 1 of the present application is configured with respect to the vortex center angle V1 that is an angle formed by the reference plane L0 and the virtual vortex center line L1. A ratio of the injection angle V that is an angle formed by the reference plane L0 and the spray center line L2, that is, a ratio represented by V / V1 (hereinafter referred to as “injection angle ratio”) is set to approximately 0.7 or less. Here, although repeated, the tumble flow 9 generally flows downward along the cylinder inner wall on the exhaust valve 5 side in the cylinder 8, flows along the top of the piston 10, and then the intake valve 4 side. This is a vortex flow of intake air flowing upward along the inner wall of the cylinder. If the fuel is injected from the fuel injection device 7 downward from the vortex center P1 of the tumble flow 9, the fuel is injected against the flow of the tumble flow. The fuel spray is hindered, and as a result, the tumble flow is attenuated. When the tumble flow is attenuated, the stirring action by the tumble flow is reduced in the latter half of the compression stroke, the homogeneity of the air-fuel mixture in the cylinder 8 is lowered, and the uneven distribution of the air-fuel mixture becomes remarkable. Even if fuel is injected from the fuel injection device 7 upward from the vortex center P1 of the tumble flow 9, since the fuel spray has a certain thickness, the lower side of the fuel spray is the flow of the tumble flow. If the fuel is jetted in opposition to the gas, the tumble flow is also partially attenuated, and it may be difficult to achieve a suitable homogenous mixture.

  Therefore, when injecting the fuel from the fuel injection device 7, from the viewpoint of forming a homogeneous air-fuel mixture, the fuel injection device 7 injects the fuel upward from the vortex center P1 of the tumble flow 9 by a certain ratio or more. It is preferable. As a result, the fuel spray is synchronized with the tumble flow in the cylinder 8 and the tumble flow and the fuel spray force are superposed to achieve more efficient homogenization of the air-fuel mixture. Then, in the internal combustion engine having a cylinder having a stroke / bore ratio (stroke / bore) of 1.0, the present applicant changes the correlation between the vortex center angle V1 and the injection angle V, and The relationship with homogenization was derived. In general, when the air-fuel ratio in the cylinder 8 is operated with stoichiometry, the concentration of carbon monoxide in the exhaust gas is regarded as an index indicating the homogeneity of the air-fuel mixture. Therefore, as shown in FIG. 3, in an internal combustion engine having a cylinder with a stroke / bore ratio (stroke / bore) of 1.0, with the air-fuel ratio set to stoichiometric, the injection angle ratio (= V / V1) and exhaust The correlation with the concentration of carbon monoxide (CO) in the solution was measured. Then, as the injection angle ratio becomes lower, the carbon monoxide concentration in the exhaust gas becomes smaller, and when the injection angle ratio becomes less than 0.7, the carbon monoxide concentration in the exhaust gas tends to be almost constant. Applicant found. Therefore, it is preferable to set the fuel injection direction of the fuel injection device 7 so that the injection angle ratio is approximately 0.7 or less.

  FIG. 4A shows the flow of fuel spray in the cylinder 8 when the injection angle ratio is 0.7 using numerical fluid dynamics (CFD), and FIG. 4B shows the cylinder 8 when the injection angle ratio is approximately 1. The flow of the fuel spray inside is shown using numerical fluid dynamics. As can be understood from these, the fuel spray tends to stay in the cylinder 8 when the injection angle ratio is large and approximately about 1, while the fuel injection device is configured by setting the injection angle ratio to 0.7. The fuel spray from 7 diffuses more uniformly in the cylinder 8.

If the injection angle ratio is made extremely small, there is a high possibility that fuel spray from the fuel injection device 7 adheres to the inner wall surface of the cylinder 8. Therefore, it is preferable not to make the injection angle ratio too small in the range of about 0.7 or less, in view of the tendency that if the injection angle ratio is about 0.7 or less, there is no significant difference in the homogeneity of the air-fuel mixture. Thereby, it becomes possible to suppress the fuel adhesion to the inner wall surface of the cylinder 8.

  Here, as the stroke / bore ratio of the cylinder 8 increases, the position of the vortex center P1 shifts further downward with respect to the injection port of the fuel injection device 7 so that the vortex center angle V1 increases. Therefore, as shown in FIG. 5, from the viewpoint of homogenization of the air-fuel mixture, it is preferable to set the injection angle V to be larger as the stroke / bore ratio of the cylinder 8 becomes larger, and the stroke / bore ratio. Regardless, the injection angle ratio is preferably set to 0.7 or less.

  As described above, the present applicant forms a homogeneous air-fuel mixture in the cylinder 8 by setting the injection angle ratio of the fuel injection device 7 to 0.7 or less in the direct injection type internal combustion engine 1. Found that it would be possible. However, according to the structure of the internal combustion engine 1 shown in FIG. 1, the fuel injection device 7 is disposed below the intake port 2. This is an extremely efficient arrangement for synchronizing the fuel spray with the intake air from the intake port 2 into the cylinder 8. Therefore, the intake valve 4 exists in the injection direction of the fuel injection device 7. In particular, when the intake valve 4 is in the maximum lift state, the intake valve 4 and the fuel spray are likely to interfere with each other, and fuel may adhere to the intake valve 4 or the cylinder head side. When such fuel adhesion occurs, the amount of fuel provided for combustion decreases, so that the desired engine output cannot be achieved, and as shown in FIG. This causes an increase in the number of PM particles and the like, and as a result, it becomes difficult to achieve suitable fuel injection by the fuel injection device 7. FIG. 6 is a diagram showing a correlation between the timing of injecting fuel from the fuel injection device 7 and the number of PM particles in the exhaust, and a line L3 is a correlation when there is interference between the intake valve 4 and fuel spray, A line L4 is a correlation when the interference does not exist. In this way, the presence of the interference results in an increase in the number of PM particles in the exhaust gas in a wide range with respect to the fuel injection timing from the fuel injection device 7, and thus a suitable fuel injection timing is determined. It becomes difficult.

  Further, in the direct injection type internal combustion engine 1, the fuel is directly injected into the cylinder 8 to cool the inside of the cylinder 8 by the heat of vaporization of the fuel, and the volumetric efficiency (ηV) of the intake air from the intake port 2. For example, WOT (Wide Open Throttle) performance can be improved. However, when the fuel spray and the intake valve 4 interfere as described above, the amount of fuel vaporized in the cylinder 8 decreases, so that sufficient cooling in the cylinder 8 cannot be performed, and the volumetric efficiency (ηV) of intake air is increased. Becomes difficult. When the injection angle ratio is set to 0.7 or less from the viewpoint of homogenization of the air-fuel mixture as described above, in short, since the injection direction of the fuel injection device 7 is set relatively upward, naturally, As shown in FIG. 7A, interference between the fuel spray and the intake valve 4 positioned in front of the fuel injection device 7 in the longitudinal section of the cylinder 8 is likely to occur.

Therefore, in the internal combustion engine 1 according to the present application, by setting the spray interference ratio between the fuel spray from the fuel injection valve 7 and the intake valve 4 to a predetermined value or less, the homogenization of the air-fuel mixture and the intake by the fuel spray interference are performed. It becomes possible to achieve both suppression of volumetric efficiency reduction. Specifically, as shown in FIG. 7B, the spray interference ratio is calculated according to the following equation.
Spray interference ratio = (ab) / a
a: Spread width of the fuel spray when there is no interference between the intake valve 4 and the fuel spray b: Spread width of the fuel spray when there is an interference with the intake valve 4 fuel spray As for the spread width of the spray, as shown in FIG. 7 (b), it is recognized that the fuel spray maintains a fan-shaped spread on the opposite side of the fuel injection device 7 with the paired intake valves 4 interposed therebetween. The width of the fuel spray at a certain place is indicated, and the spread width according to a and b is the width of each fuel spray at a common place.

When the spray interference ratio is set in this way, it means that the ratio at which the fuel spray from the fuel injection device 7 interferes with the intake valve 4 and adheres increases as the spray interference ratio increases. Therefore, in the internal combustion engine 1 of the present application, by setting the spray interference ratio to 0.7 or less, it is possible to achieve both homogenization of the air-fuel mixture and improvement in volume efficiency and engine output in the internal combustion engine 1. I found out that The upper diagram of FIG. 8 shows a volume efficiency improvement allowance (indicated by line L5 in the figure) in a conventional intake port injection type internal combustion engine and a volume efficiency improvement allowance (indicated by line L6 in the figure) of the internal combustion engine 1 according to the present application. Is shown). 8 shows a torque improvement allowance (indicated by a line L7 in the figure) in a conventional intake port injection type internal combustion engine and a torque increase allowance (indicated by a line L8 in the figure) in the internal combustion engine 1 according to the present application. It is).

  As described above, in the internal combustion engine 1 according to the present application, the homogenization of the air-fuel mixture in the cylinder 8 is improved by setting the injection angle ratio to 0.7 or less, and the spray interference ratio is 0.7 or less. By doing so, interference between the intake valve 4 and the fuel spray is suppressed. As a result, as shown in FIG. 8, the internal combustion engine 1 can exert an advantage over the conventional intake port injection type internal combustion engine with respect to the volume efficiency improvement margin and the torque improvement margin at almost the entire engine speed. .

<Other examples>
In the above-described embodiments, in the cylinder direct injection type spark ignition internal combustion engine having the ignition plug, the homogenization of the air-fuel mixture is improved by setting the injection angle ratio to 0.7 or less, and the spray interference ratio is further increased. In the present invention, the volumetric efficiency of the intake air in the cylinder 8 is improved by setting the value to a predetermined value or less. Here, the present invention can also be applied to an in-cylinder direct injection type compression ignition internal combustion engine. In general, a compression ignition internal combustion engine has a fuel injection device that directly injects fuel into a cylinder. By using the fuel injection device, the compression ignition internal combustion engine enters the cylinder at a timing before fuel injection near the top dead center of the compression stroke. In some cases, fuel is injected into the cylinder from the fuel injection device to form a premixed gas. In such a case, the above-described invention of the present application may be applied to form a tumble flow in the cylinder and to synchronize the fuel spray appropriately with the tumble flow. Moreover, in order to suppress the interference between the intake valve and the fuel spray as much as possible, the present invention described above may be applied.

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Intake port 3 ... Exhaust port 4 ... Intake valve 5 ... Exhaust valve 6 ... Spark plug 7 ... Fuel injection device 7a ... Fuel spray 8 ... Cylinder 9 ... Tumble flow 10 ... Piston 11a ... Partition 11b ... Shut-off valve

Claims (4)

A fuel injection device that is provided in the vicinity of the intake valve and directly injects fuel into the cylinder;
An internal combustion engine comprising: a tumble flow generating mechanism that generates a tumble flow in a longitudinal direction in a cylinder by opening and closing the intake valve;
In the internal combustion engine, a tumble flow generated in the cylinder by the tumble flow generation mechanism at a predetermined timing of the intake stroke is formed by connecting an assumed vortex center of the tumble flow and an injection port of the fuel injection device. The angle formed by the vortex center line and the reference plane extending in the radial direction of the cylinder is defined as the vortex center angle,
An angle formed by a center line of the fuel spray injected from the fuel injection device in the longitudinal extension of the cylinder and the reference plane is defined as an injection angle.
The fuel injection device performs fuel injection below the reference plane in the cylinder,
The ratio of the injection angle to the vortex center angle is set to 0.7 or less.
Internal combustion engine. The predetermined time is a time in the vicinity of the intake bottom dead center in the intake stroke of the internal combustion engine.
The internal combustion engine according to claim 1. The fuel spray injected from the fuel injection device is a spray having a fan-shaped fan shape.
The internal combustion engine according to claim 1 or 2. When the fuel spray injected from the fuel injection device interferes with the intake valve when the intake valve is in the maximum lift state for opening the valve, it is assumed that there is virtually no interference with the intake valve. A spray interference ratio defined as a ratio of the spray width interfered by the intake valve when there is interference with the intake valve with respect to the spray width of the fuel spray is 0.7 or less;
The internal combustion engine according to claim 3.

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