JP2000220460A - Cylinder injection type internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain good lean-burning not depending on the engine speed at low and medium load driving even of a flat type piston in a spark ignition engine to inject fuel directly to a cylinder in an internal combustion engine. SOLUTION: An internal combustion engine is provided with an ignition plug 6 and a fuel injection valve 5 to inject fuel directly in a cylinder. A cylinder center axis is defined as Z axis, an axis crossing with the Z axis vertically and passing through a gravitational point of the cylinder and a point directly under the fuel ignition valve 5 is defined as X axis, and an axis passing through the gravitational point of the cylinder, which is perpendicular to the X axis and the Z axis is defined as Y axis. At that time, airflow turning around the center of the axis is formed in a cylinder 1. Injected fuel 16 is set so that the fuel injection quantity control can be carried out. In this case, air-fuel ratio becomes higher than stoichiometric air-fuel ratio under an atomization state where the spray angle perpendicular to the XZ plane becomes narrower than the spray angle parallel to the XZ plane in the low and medium load driving. Fuel is injected during the periods from the latter half of the intake stroke to the former half of the compression stroke.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct injection type internal combustion engine in which fuel is directly injected into a cylinder of a spark ignition engine using a spark plug.

[0002]

2. Description of the Related Art In recent years, an in-cylinder injection type internal combustion engine that directly injects fuel into a cylinder of a spark ignition engine (gasoline engine) has been put to practical use. This type of internal combustion engine performs combustion by injecting fuel during a compression stroke in a low to medium load region and locally collecting and spraying a fuel spray around an ignition plug (also referred to as stratification of a mixture or stratified combustion). is there)
Lean air-fuel ratio combustion (hereinafter simply referred to as lean combustion) is possible, and in the high load operation range, it is necessary to uniformly mix fuel with air to achieve homogeneous combustion, so that fuel is injected during the intake stroke. The fuel injection start timing is changed according to the load.

Further, in order to achieve the above-described stratified combustion, a direct injection type spark ignition is provided in which a concave portion is provided on the upper surface of a piston to inject fuel into the concave portion during a compression stroke of a low-to-medium load operation to stratify the concave portion. In an engine (in-cylinder injection type internal combustion engine) or (for example, JP-A-4-94416), an intake pipe is provided with a sub-intake passage, and an air flow supplied from the sub-intake passage flows along a concave portion provided in the upper part of the piston. An in-cylinder injection internal combustion engine that stratifies fuel spray by transferring it to an ignition plug (Japanese Patent Laid-Open No. 10-141)
070 publication) has been proposed.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a spark igniter for lean combustion (during low-to-medium load operation) even if the upper surface is a flat piston without providing a recess on the upper surface of the piston as described above. It is an object of the present invention to provide an in-cylinder injection type internal combustion engine capable of achieving excellent stratified combustion, improving thermal efficiency and improving ignition performance, and satisfying requirements for fuel efficiency, exhaust gas purification, and output increase.

[0005] In addition, there is also provided an in-cylinder injection type internal combustion engine capable of uniformly forming an air-fuel mixture in a cylinder and performing homogeneous combustion during high load operation in addition to favorable lean combustion during low and medium load operation.

[0006]

Means for Solving the Problems (1) The present invention basically proposes the following means for solving the problems in order to achieve the above object.

That is, in a cylinder injection type internal combustion engine having an ignition plug and injecting fuel directly into a cylinder by a fuel injection valve, the cylinder center axis of the internal combustion engine intersects perpendicularly with the Z axis and the Z axis, and the center of gravity of the cylinder is When an axis passing through a point immediately below the position where the fuel injection valve is arranged is defined as an X axis, and an axis passing through the center of gravity of the cylinder and perpendicular to the X axis and the Z axis is defined as a Y axis,
Means for forming an air flow which rotates around the Y axis in the cylinder, wherein the fuel injected from the fuel injection valve has a spray angle in a direction perpendicular to the XZ plane in a direction parallel to the XZ plane during low to medium load operation. The fuel injection amount control is performed such that the air-fuel ratio becomes higher than the stoichiometric air-fuel ratio in the spray mode in which the spray angle is smaller than the spray angle.

According to the above-described structure, the fuel injected into the cylinder during the low-to-medium-load operation uses an air flow around the Y axis (this air flow is not a swirl swirling around the cylinder axis but a so-called orthogonal to the cylinder axis). To rotate around the axis
Here, the fuel is conveyed to the spark plug by riding on a spark plug (sometimes referred to as a tumble for the purpose of distinguishing the swirl from the above-described swirl), so that fuel injection into the cylinder is started during the latter half of the intake stroke and the earlier half of the compression stroke. Even if it is set, the fuel injection start timing can be set so that the injected fuel spray reaches the spark plug by the above-mentioned tumble near the top dead center during the piston compression stroke.

The fuel spray at this time is a so-called vertical flat spray in which the spray angle in the direction perpendicular to the XZ plane is smaller than the spray angle in the direction parallel to the XZ plane. By riding the flow, the fuel spray is concentrated near the spark plug even with a flat type piston that does not have a concave part on the piston upper surface, as a result, good fuel ignition and combustion is achieved, and the air-fuel ratio is higher than the stoichiometric air-fuel ratio It enables lean combustion at an air-fuel ratio with increased leanness by controlling the fuel injection amount.

During high load operation, the fuel injection is started during the intake stroke so that the fuel and air are sufficiently mixed, or the fuel is injected from a plurality of fuel injection ports. If the spray angle in the direction perpendicular to the XZ plane is set to be wider than the spray angle in the direction parallel to the XZ plane, a uniform air-fuel mixture is formed in the cylinder, and good homogeneous combustion becomes possible.

[0011]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic plan view of an internal perspective view of one of cylinders taken out of a direct injection internal combustion engine (direct injection spark ignition engine) according to a first embodiment of the present invention. 7A is a longitudinal sectional view thereof, and FIG. 7B is an explanatory diagram of coordinate axes defined in the present embodiment.

First, the gist of the present invention will be described with reference to these drawings.

The piston 2 provided in the cylinder 1 is a so-called flat type piston whose upper surface is formed in a flat surface without a concave portion.

The head of the cylinder 1 has two intake valves 4
Are arranged, and each intake valve 4 and the corresponding intake pipe (intake passage) 3
And are connected. Although the number of exhaust valves also corresponds to the number of intake valves, illustration of the exhaust valves and the exhaust pipe connected thereto is omitted.

An ignition plug 6 is provided at the center of the head of the cylinder 1, and a fuel injection valve 5 is provided at a position between the intake valves 4.

Here, as shown in FIG. 7 (b), an axis which intersects the cylinder center axis perpendicularly to the Z axis and passes through the center of gravity of the cylinder and the point immediately below the position where the fuel injection valve 5 is arranged is shown. Is defined as the X axis, and the axis passing through the center of gravity of the cylinder and perpendicular to the X axis and the Z axis is defined as the Y axis.

In this case, the fuel injection valve 5 is arranged on the XZ plane, and the intake valve 4 is arranged so as to sandwich the XZ plane.

The intake pipe 3 located upstream of the intake valve 4 includes:
A half-moon-shaped air flow control valve 8 is provided which is controlled to close the lower half of the passage cross section during low-medium load operation. Since the control valve 8 has a half-moon shape, the state in which the lower half passage is closed is closed. During a high load operation, the lower half passage is opened and the upper half is originally open. It is completely open. The control valve 8 is arranged downstream of a throttle valve (not shown) for controlling an air flow rate. Opening / closing control of the control valve 8 is executed by the control device 7 based on a control command signal. The control device 7 also controls the fuel injection rate of the fuel injection valve 5, controls the injection start timing, controls the ignition timing of the ignition plug, and the like.

When the lower half of the flow path (lower half of the cross section of the intake passage) of the intake pipe 3 is closed by the control valve 8, as shown in FIG. After the air flows in the upper half flow path of the intake pipe 3, air flows into the cylinder 1 through a side of the intake valve 4 closer to the ignition plug (center side of the cylinder 1), and then flows in a direction opposite to the intake side. An air flow (hereinafter, referred to as a tumble) that rotates around the Y axis in the cylinder 1 is formed.

The angular velocity of the tumble is set to tumble number 2. The tumble number is defined as a ratio (ωa / ω) of the angular velocity ωa of the vortex (air flow) and the angular velocity ωc of the crankshaft when a rigid vortex (ideal vortex of the tumble) is assumed in the cylinder 1.
where tumble number 2 is the angular velocity ω of the rigid body vortex
c is twice the angular speed ωa of the crankshaft. When the tumble number is set in this manner, when fuel is injected near the bottom dead center of the intake stroke (in the present embodiment, fuel injection into the cylinder 1 is performed during the second half of the intake stroke and the first half of the compression stroke during low to medium load operation. (Set to start), the fuel can be transported in a tumble airflow so as to concentrate on the position of the ignition plug 6 near the top dead center.

More specifically, when fuel is conveyed to the position of the ignition plug 6 by tumble, the number of tumbles required to reach the ignition plug 6 through the cylinder 1 changes depending on the fuel injection timing. The number of tumbles required for stratification is determined by the crank angle from fuel injection to ignition.
In this case, it is a value obtained by dividing 360 degrees corresponding to one rotation of the crank angle by the angle T. That is, assuming that the crank angle from fuel injection to ignition is T, the angular velocity ωa of the tumble (air flow) is obtained by multiplying the crankshaft angular velocity ωc by a value obtained by dividing 360 degrees corresponding to one rotation of the crank angle by the angle T. This is a value, which can be expressed by the following equation.

[0023]

Ωa = (360 ° / T) × ωc For example, when the fuel injected at the bottom dead center is set at the top dead center as the ignition timing, the crank angle T is 180 degrees, and 360 degrees is 180 degrees. The divided value of 2 is the number of tumbles required for stratification. When the controller 7 determines the required number of tumbles from the fuel injection timing, the controller 7 controls the closing operation timing of the control valve 8 (the timing to close the lower half of the passage cross section of the intake pipe) to control the cylinder 1.
Form the required tumble within. During high load operation, tumble control is not required, and the control valve 8 is fully opened to reduce pressure loss.

Here, the internal structure of the fuel injection valve 5 used in this embodiment will be described with reference to a partial longitudinal sectional view of FIG.

In FIG. 2, a main fuel passage 12 is formed at the center of the main body of the fuel injection valve 5, and thereafter is divided into a plurality of fuel passages 14a to 14c.
9c. A core 21, an electromagnetic coil 11, and a yoke 22 are arranged concentrically with the fuel passage 12. When the electromagnetic coil 11 is energized and excited, a magnetic circuit is formed by the core, the yoke, the plunger portion of the valve 10, and the like. It is pulled up against the spring force of the return spring 24, and the valve is opened.

As shown in FIG. 2, the fuel injection valve 5 provided in the cylinder 1 has a plurality (three in this embodiment) of fuel injection ports (hereinafter, referred to as injection ports) 9a, 9b, 9c. These injection ports 9 a, 9 b, 9 c are formed by a combination of holes provided in a plurality of layers (for example, three layers) of the plate 13 provided at the tip of the fuel injection valve 5.

The three jet ports 9a, 9b, 9c are Y
In the axial direction, one of them (injection port 9a) is located in the middle, and the remaining 9b and 9c are located on both sides of the central ejection port 9a. There is provided an injection port switching means for injecting fuel from the injection ports 9a, and for injecting fuel from the injection ports 9b, 9c on both sides during high load operation. Here, an example of the injection port switching means will be described.

The fuel injection valve 5 changes the amount of current flowing through the coil 11 depending on the operation state of the internal combustion engine, and changes the lift amount of the valve 10 to thereby change the fuel flow paths 14a and 1a in the injection valve body.
4b and 14c can be switched. In the case of low and medium load operation, a weak current is caused to flow through the coil 11 and the lift amount of the valve 10 is controlled to be small, thereby selecting the fuel flow path 14a communicating with the injection port 9a as shown in FIG. In this case, by passing a strong current through the coil 11 and controlling the lift amount of the valve 10 to be large, the fuel flow paths 14b, 14c leading to the injection ports 9b, 9c as shown in FIG.
Is set to be selected.

As shown in FIG. 5A, the multilayer plate 13 is composed of three circular metal plates (a metal plate having excellent corrosion resistance and heat resistance) 13
a, 13b, 13c, circular holes 9b-1, 9a-1, 9c-1 are formed in the upper plate 13a, and elongated holes 9b-2, 9a-2, 9c-2 are formed in the middle plate 13b. However, in the lower layer, the plate 13c is provided with the elongated holes 9b-3, 9a-3, 9c-3 each of which corresponds to the number of the fuel injection ports, which cross the elongated holes of the middle layer. 5b, each fuel injection port 9b, 9a, 9c is formed. Of these, the lower slot 9b-3, 9a-3, 9c-3 has the longitudinal direction XZ. Orients parallel to the plane.

The fuel passes through the injection port 9a during low and medium load operation, and passes through the injection ports 9b and 9c during high load operation to be atomized and become fuel spray. The fuel spray injected from the injection port 9a during low-medium load operation employs the above-described structure of the injection port 9a, so that the spray angle θ1 in the direction perpendicular to the XZ plane (Y-axis direction) as shown in FIG. Is smaller than the spray angle θ2 in the direction parallel to the XZ plane. Further, the control device 7 is set to perform the fuel injection amount control at which the air-fuel ratio becomes higher than the stoichiometric air-fuel ratio during the low and medium load operation.

The spray angles θ1 and θ2 shown in FIG. 6 are determined as follows.

The spray angle θ1 is as follows. As shown in FIG. 25 (a), an isosceles triangle having an angle θ is assumed, and the angle θ is defined as L, where L is the base length when the stroke length of the piston in the cylinder is the height H of the isosceles triangle. The cylinder inner diameter D × L × stroke length H
In the virtual cuboid inside the cylinder (indicated by oblique lines in FIG. 25B), the total injected fuel amount is an angle capable of forming an air-fuel mixture having a stoichiometric mixture ratio. The fuel spray angle θ1 in the vertical direction was set. If stratified combustion is possible in such a virtual rectangular parallelepiped, the stoichiometric air-fuel ratio can be substantially reduced even in a lean burn region (particularly, a super-lean burn where the ratio of fuel mass to air mass is 1:40). Close combustion becomes possible. In this embodiment, the fuel spray angle θ1 as described above is used.
And the fuel spray within the fuel spray angle θ1 is transported by tumble from the two intake valves so as to reach the ignition plug 6 during the compression stroke, thereby ensuring good lean combustion (stratified combustion).

The spray angle θ2 is an angle that does not collide with the upper wall surface of the cylinder head 1 or the wall surface on the intake side of the cylinder 1 when the outer shape of the fuel spray is extended.

Spouts 9b, 9 used during high load operation
The dimension of c is the same as that of the jet port 9a, but the direction of the jet port is slightly inclined outward so that the fuel sprays injected from the jet ports 9b and 9c do not intersect. The angle is an angle at which the injected fuel does not hit the side wall surface of the cylinder 1.

In order to satisfactorily burn an air-fuel mixture having a higher air-fuel ratio (lean air-fuel ratio) than the ideal air-fuel ratio during low to medium load operation, stratification is necessary as described above. Although fuel was injected in the latter half of the compression stroke, in this case, when the piston 2 approaches the top dead center, the fuel is injected so that the fuel spray and the tumble strike from the front, the tumble stops, and the fuel is injected into the spark plug. It is also conceivable that the distribution cannot be distributed to No. 6 and no ignition occurs.

On the other hand, when the fuel injection start timing is set to the piston bottom dead center as in the present embodiment, the interference between the tumble and the fuel spray is small, and the mixture can be conveyed to the spark plug by the tumble. At the time of high load operation, the fuel needs to be sufficiently mixed with the air. Therefore, the fuel injection start timing is a timing at which the fuel is completely injected before the piston 2 reaches the bottom dead center of the intake stroke.

Hereinafter, the operation of the present embodiment will be described in detail with reference to FIGS.

First, the low-medium load operation (lean combustion) will be described.

In the initial stage of the intake stroke (suction stroke), the fuel injection start timing is set at the bottom dead center.
Fully closes the control valve 8 in order to generate a tumble number 2 air flow in the cylinder 1.

When the intake stroke starts, the intake valve 4 opens and the piston 2 descends, so that air is sucked into the cylinder 1 and a tumble 15 having a strength of 2 is generated (FIG. 7).

When the piston 2 reaches the bottom dead center, the control device 7 sends a fuel injection signal to the fuel injection valve 5. At this time, a weak current flows through the coil 11 to generate a magnetic field on the outer periphery of the coil 11, the valve 10 is lifted upward, fuel flows through the flow path 14a, and the fuel is atomized from the ejection port 9a formed by the multilayer plate 13. Injected to form a fuel spray 16. The mass of fuel injected is 1 of the mass of air taken into cylinder 1.
/ 40.

8 and 9 show the inside of the cylinder 1 during the compression stroke. FIG. 9 is a view of the inside of the cylinder 1 as viewed from above, and FIG. 9 is a view as viewed from the side. Since the intake valve 4 is already closed, the description is omitted together with the intake pipe 3. The fuel spray 16 is vaporized to form a mixture 17 of fuel and air, and is conveyed to the tumble 15 to reach the surface of the piston 2. The air flow in the cylinder 1 is only the tumble 15, and the air-fuel mixture 17 is not easily diffused in a direction perpendicular to the tumble 15, and the air-fuel mixture 17 is held at the center of the cylinder 1.

FIGS. 10 and 11 show the inside of the cylinder 1 at the ignition timing when the piston 2 reaches the top dead center. FIG. 10 is a view of the inside of the cylinder 1 as viewed from above, and FIG. 11 is a view as viewed from the side. The mixture 17 is conveyed to the tumble 15 and reaches the spark plug 6. Total fuel injection amount is 1/4 of air
Although the operating condition is as low as 0, the mixture 17 around the spark plug 6
, A sufficient air-fuel mixture close to the stoichiometric air-fuel ratio is obtained, and good combustion is possible. Further, since the number of tumbles generated in the cylinder when the engine speed becomes high is constant, the stratification can be stably realized by transporting the air-fuel mixture by tumbling even at a low load and a high speed.

FIGS. 12 and 13 show a state in which the piston 2 is at the bottom dead center during the high load operation. FIG. 12 is a view of the cylinder 1 seen from above, and FIG. It is the figure seen from the side.

In the high load operation, the control device 7 fully opens the control valve 8 in order to obtain a high output. When the intake stroke starts, the intake valve 4 opens and the piston 2 descends, so that the intake valve 4
Although air flows into the cylinder 1 from the surrounding gap, the force of the air flow on the opposite side of the fuel injection valve 5 exceeds the force of the air flow in the part as shown by reference numeral 15 to form the tumble 15.

The control device 7 sends a signal to the fuel injection valve 5 so as to inject fuel at the fuel injection start timing. At this time, a strong current flows through the coil 11, and a magnetic field is generated around the coil 11, and the valve 10 is lifted up. When the valve 10 is lifted, fuel flows into the flow paths 14 b and 14 c, and the fuel is atomized and injected from the outlets 9 b and 9 c formed by the multilayer plate 13 to form a fuel spray 16. The fuel injection amount during the high-load operation is 1 / 14.7 (stoichiometric air-fuel ratio) of the mass of air flowing into the cylinder 1. Spout 13b, 1
By injecting fuel from the two injection ports 3c, the spray angle is increased, and the injection ports are directed outward, so that the fuel spray 16 spreads throughout the cylinder 1.

FIGS. 14 and 15 show the cylinder 1 during the compression stroke.
14 is a view of the inside of the cylinder 1 as seen through from above, and FIG. 15 is a view as seen from the side. Since the intake valve 4 is already closed, the description is omitted together with the intake pipe 3.

The fuel spray 16 is vaporized to form a mixture 17 of fuel and air, and is conveyed to the tumble 15 to reach the surface of the piston 2. By the time the piston rises and reaches the end of the compression stroke, the mixture 17 is dispersed by the tumble 15 to form a uniform mixture throughout the cylinder 1.
At this time, the air-fuel ratio of the air-fuel mixture satisfactorily burns at a theoretical mixture ratio of 14.7.

Next, a second embodiment of the present invention will be described with reference to FIGS.
3 will be described.

The tumble forming means (arrangement of the control valve 8), the arrangement of the intake valve 4, the flat piston structure, and the fuel spray form at the time of low-medium load operation of the direct injection internal combustion engine according to this embodiment are shown in FIG. Since the configuration is the same as that shown in FIGS. 1 and 7, illustrations corresponding to FIGS. 1 and 7 are omitted. Example 1 and Example 1
The difference from the embodiment is that the internal structure of the fuel injection valve 5 is different.

As shown in FIG. 16, the fuel injection valve 5
There are two injection ports 9d and 9e, and the injection ports are constituted by a multilayer plate 13 provided at the tip of the fuel injection valve 5. The fuel injection valve 5 is installed so that these two injection ports are arranged in the Y-axis direction. A valve 10 is provided upstream of the fuel outlet, and when a current flows through the coil 11, a magnetic field is generated to move the valve 10 upward and fuel is injected from the injection port.

The amount of current flowing through the coil 11 is varied depending on the operation state of the internal combustion engine, and the lift amount of the valve 10 is changed. In the case of low-medium load operation, the lift amount of the valve 10 is determined so that a weak current flows through the coil 11 and the fuel flowing from the inlet 12 selects the flow path 14d. In the case of a high-load operation, a strong current flows through the coil 11, and the lift amount of the valve 10 is determined so that the fuel flowing from the inlet 12 selects the flow path 14e. In the case of low-medium load operation, as shown in FIG.
In the case of high load operation, fuel is injected from the injection port 9e as shown in FIG.

As shown in FIG. 17, the multilayer plate 13 is composed of three metal plates 13a, 13b and 13c, and the upper, middle and lower metal plates are respectively provided with jets 9d,
Circular holes 9d-1, 9e-1 for forming 9e, elongated (rectangular) holes 9d-2, 9e-2 and 9d-3, 9e-
3 are open, and the spouts 9d and 9e are formed by overlapping these holes.

The fuel is atomized by passing through the holes 9d and 9e and becomes a fuel spray. The shape of the spout 9d is exactly the same as the spout 9a of the first embodiment. The elongated holes 9e-2 and 9e-3, which are elements of the ejection port 9e, are connected to the ejection port 9d-
It is rotated 90 degrees with respect to 2, 9d-3, respectively.
The spray shape of the ejection port 9e is as follows.
The fuel spray angle is rotated by degrees, and the fuel spray angle θ1 perpendicular to the XZ plane is larger than the fuel spray angle θ2 parallel to the XZ plane.

The fuel injection start timing, the number of tumbles required for stratification, and the method of generating the tumbles in this embodiment are the same as those in the first embodiment, and these information are set in the control device 7.

The operation at the time of low-to-medium load operation is the same as that of the first embodiment, and therefore will not be described, and the operation at the time of high-load operation will be described.

FIGS. 20 and 21 show the inside of the cylinder 1 when the piston 2 is at the bottom dead center during the high-load operation. FIG. 21 is a diagram viewed from the side.

In high-load operation, the control device 7 fully opens the control valve 8 in order to obtain a high output. When the intake stroke starts, the intake valve 4 opens and the piston 2 descends, so that air flows into the cylinder 1 through a gap formed around the intake valve 4, and the position at which the fuel injection valve 5 falls as described above. The air flow force on the side away from the other air flow exceeds the other air flow to form the tumble 15.

The control device 7 sends a signal to the fuel injection valve 5 so as to inject fuel at the fuel injection start timing. At this time, a strong current flows through the coil 11, and a magnetic field is generated around the coil 11, and the valve 10 is lifted up. When the valve 10 is lifted, fuel flows into the flow path 14e, and the multilayer plate 13
The fuel is atomized and injected from the injection port 9e formed by the above to form a fuel spray 18. In this embodiment, the spout 14
By providing e rotated by 90 degrees, the spray angle θ1 of the fuel spray becomes large, and the fuel is easily dispersed.

FIGS. 22 and 23 show cylinders 1 during the compression stroke.
It is shown inside. FIG. 22 is a view of the inside of the cylinder 1 as viewed from above, and FIG. 23 is a view as viewed from the side. Since the intake valve 4 is already closed, the description is omitted together with the intake pipe 3. The fuel spray 18 is vaporized to form a mixture 17 of fuel and air, and is conveyed to the tumble 15 to reach the surface of the piston 2. By the time the piston rises and reaches the end of the compression stroke, the mixture 17 is diffused by the tumble 15 to form a uniform mixture throughout the cylinder 1. At this time, the air-fuel ratio of the air-fuel mixture satisfactorily burns at a theoretical mixture ratio of 14.7.

FIG. 24 shows a third embodiment of the present invention, which has the same configuration as that of the first embodiment except for the following points.

That is, in the present embodiment, as shown in FIG. 24, the speed component V2 on the piston side of the spray spread in the direction parallel to the XZ plane of the fuel spray 16 is made larger than the speed component V1 on the cylinder head side. . By providing a speed difference between V1 and V2 of the fuel spray 16 in this way, it is possible to prevent the fuel spray 16 from adhering to the inner wall of the cylinder 1. In particular, the situation where the fuel spray of the speed component V1 traverses the cylinder and adheres to the inner wall of the cylinder is prevented. As a method of providing this speed difference, it is conceivable to cut the flow path length of the fuel injection port obliquely.

[0063]

According to the present invention, during low-medium load operation, a tumble is generated in the cylinder, and a fuel spray having a thin spray width in a direction perpendicular to the XZ plane is injected at the bottom dead center of the piston.
Since the optimal mixture of tumble is used to concentrate the mixture near the stoichiometric air-fuel ratio near the ignition plug during the compression stroke, good lean combustion (even during low-medium load operation) can be achieved without being affected by the engine speed even with a flat piston. Stratified combustion). Further, at the time of high load operation, it is possible to obtain a good combustion by widening the fuel spray and uniformly distributing the air-fuel mixture in the cylinder.

Further, according to the present invention, in order to enable better stratified combustion with the flat type piston, heat loss is reduced (improvement of thermal efficiency) as compared with the case where the piston recess is provided, and air inside the piston is further improved. Flow resistance can be reduced and tumble forming force can be sufficiently ensured.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a bottom dead center of a piston at the time of lean burn in a first embodiment of the present invention seen through from a cylinder upper surface.

FIG. 2 is a partially omitted sectional view of a fuel injection valve used in the embodiment.

FIG. 3 is a cross-sectional view illustrating a part of the fuel injection valve during lean combustion according to the first embodiment.

FIG. 4 is a cross-sectional view showing a part of the fuel injector during homogeneous combustion according to the first embodiment.

FIG. 5 is an exploded perspective view of a multilayer plate having a fuel injection port according to the first embodiment and a plan view seen from a lower layer side.

FIG. 6 is an explanatory diagram of a fuel spray angle inside a cylinder during lean combustion according to the first embodiment.

FIG. 7 is a sectional side view of a cylinder showing a state of a piston bottom dead center at the time of lean combustion according to the first embodiment, and an explanatory diagram showing coordinate axes of the cylinder.

FIG. 8 is a schematic top view showing a compression stroke at the time of lean combustion according to the first embodiment as seen through the inside of a cylinder.

FIG. 9 is a side cross-sectional view showing the inside of the cylinder in the compression stroke during lean combustion according to the first embodiment.

FIG. 10 is a top view of the state of the top dead center of the piston at the time of lean combustion in the first embodiment, as seen through the inside of the cylinder.

FIG. 11 is a side sectional view of the cylinder showing a state of the piston top dead center at the time of lean combustion according to the first embodiment.

FIG. 12 is a top view of the state of the piston bottom dead center during homogeneous combustion according to the first embodiment, as seen through the inside of the cylinder.

FIG. 13 is a side cross-sectional view of the cylinder showing a state of the piston bottom dead center during homogeneous combustion according to the first embodiment.

FIG. 14 is a top view of the compression stroke during homogeneous combustion according to the first embodiment as seen through the inside of the cylinder.

FIG. 15 is a side cross-sectional view of the cylinder illustrating a state of a compression stroke during homogeneous combustion according to the first embodiment.

FIG. 16 is a partial cross-sectional view of a fuel injection valve used in the second embodiment.

FIG. 17 is an exploded perspective view of a multilayer plate forming an injection port of the fuel injection valve according to the second embodiment, and a plan view seen from a lower layer side thereof.

FIG. 18 is a partial cross-sectional view of the fuel injection valve during lean combustion according to the second embodiment.

FIG. 19 is a partial cross-sectional view of the fuel injection valve during homogeneous combustion according to the second embodiment.

FIG. 20 is a top view of the state of the bottom dead center of the piston during homogeneous combustion in Example 2 as seen through the inside of the cylinder.

FIG. 21 is a side cross-sectional view of a cylinder showing a state of a piston bottom dead center during homogeneous combustion according to the second embodiment.

FIG. 22 is a top view of the state of the compression stroke during homogeneous combustion according to the second embodiment as seen through the inside of a cylinder.

FIG. 23 is a side cross-sectional view of the cylinder showing a state of a compression stroke during homogeneous combustion according to the second embodiment.

FIG. 24 is a side sectional view showing the inside of the cylinder of the third embodiment.

FIG. 25 is an explanatory diagram showing the relationship among a spray angle of fuel injected into a cylinder, a cylinder inner diameter D, a base L of a virtual isosceles triangle of fuel spray, and a cylinder height (stroke) H, and D × L × FIG. 4 is an explanatory diagram showing an ideal mixture formation space formed in the cylinder at the time of lean combustion by H.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Cylinder, 2 ... Piston, 3 ... Intake pipe, 4 ... Intake valve, 5 ... Fuel injection valve, 6 ... Spark plug, 7 ... Control device,
8. Air flow control valve, 9a, 9b, 9c, 9d, 9e ...
Injection port (fuel injection port), 10 ... valve, 11 ... coil, 12
... fuel inlet, 13 ... multilayer board, 14a, 14b, 14c,
14d, 14e: flow path, 15: tumble, 16: fuel spray, 17: mixture, 18: fuel spray.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02M 61/14 310 F02M 61/14 310A 61/18 350 61/18 350A (72) Inventor Takuya Ishiga Ibaraki 7-1-1, Omika-cho, Hitachi City Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Takuya Shiraishi 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture F-term in Hitachi Research Laboratory, Hitachi, Ltd. (Reference) 3G023 AA01 AA18 AB03 AC05 AD03 AD07 AD09 AD14 AD27 AG01 AG02 3G066 AA02 AA03 AA05 AD12 BA01 BA03 CC01 CC21 CC37 CC48 DB06 DB08 DB09 3G301 HA01 HA04 HA16 HA17 JA00 KA06 KA08 KA09 LA05 LB04 MA01 MA11 MA01BZZA01 P03

Claims (13)

[Claims] 1. An in-cylinder injection type internal combustion engine having a spark plug and injecting fuel directly into a cylinder by a fuel injection valve, wherein the cylinder center axis of the internal combustion engine intersects perpendicularly with the Z axis and the cylinder center of gravity. When an axis passing through the point immediately below the position where the fuel injection valve is disposed is defined as the X axis, and an axis passing through the center of gravity of the cylinder and perpendicular to the X axis and the Z axis is defined as the Y axis, the center of the cylinder is defined as the Y axis. Means for forming a rotating air flow, wherein the fuel injected from the fuel injector has a spray form in which the spray angle in the direction perpendicular to the XZ plane is smaller than the spray angle in the direction parallel to the XZ plane during low to medium load operation. Wherein the fuel injection amount control is performed such that the air-fuel ratio becomes higher than the stoichiometric air-fuel ratio. 2. The in-cylinder injection type internal combustion engine according to claim 1, wherein the fuel injection valve is set to start fuel injection into the cylinder during a low-medium load operation during a second half of an intake stroke and a first half of a compression stroke. organ. 3. The angular velocity ωa of the air flow rotating about the Y axis is defined as 360 ° which is one rotation of the crank angle, where T is the crank angle from fuel injection to ignition.
3. The direct injection internal combustion engine according to claim 1, wherein a value obtained by multiplying the divided value by a crankshaft angular velocity ωc is obtained. 4. The cylinder head has two intake valves disposed so as to sandwich the XZ plane, and each intake passage communicating with the intake valve has a lower half of a cross section of the intake passage during low-medium load operation. Air flow control valve is provided to block
4. The direct injection internal combustion engine according to claim 1, wherein said air flow control valve constitutes means for forming an air flow rotating about the Y axis in said cylinder. 5. The direct injection internal combustion engine according to claim 1, wherein a velocity component on a piston side of the spray spread in a direction parallel to the XZ plane is larger than a velocity component on a cylinder head side. organ. 6. The fuel injected from the fuel injection valve is set such that a spray angle in a direction perpendicular to the XZ plane is wider than a spray angle in a direction parallel to the XZ plane during high load operation. 6. The direct injection internal combustion engine according to claim 5. 7. An in-cylinder injection type internal combustion engine having an ignition plug and injecting fuel directly into a cylinder by a fuel injection valve, wherein the cylinder center axis of the internal combustion engine intersects perpendicularly with the Z axis and the cylinder center of gravity. When an axis passing through the point immediately below the position where the fuel injection valve is disposed is defined as the X axis, and an axis passing through the center of gravity of the cylinder and perpendicular to the X axis and the Z axis is defined as the Y axis, The fuel injection valve includes a plurality of fuel injection ports that form a fuel spray in which a spray angle in a direction perpendicular to the XZ plane is smaller than a spray angle in a direction parallel to the XZ plane. Among them, it is set that fuel is injected from one fuel injection port at the time of low-medium load operation, fuel is injected from two or more fuel injection ports at the time of high load operation, and the air-fuel ratio is low at the time of low-medium load operation. Higher than stoichiometric air-fuel ratio An in-cylinder injection type internal combustion engine comprising means for controlling a fuel injection amount. 8. A plurality of fuel injection ports are arranged in the Y-axis direction, one of which is located in the middle and the other is located on both sides of the center fuel injection port. 8. An in-cylinder injection type internal combustion engine according to claim 7, further comprising injection port switching means for injecting fuel from said middle fuel injection port during load operation and injecting fuel from both fuel injection ports during high load operation. 9. A multi-layer plate is provided at a tip of the fuel injection valve,
This multilayer plate is a metal plate, a circular hole is formed in the upper layer, an elongated hole is formed in the middle layer, and an elongated hole which crosses the elongated hole of the middle layer is formed in the lower layer by the number of fuel injection ports, respectively. 9. The direct injection internal combustion engine according to claim 8, wherein each of the fuel injection ports is formed by overlapping a circular hole and a crossed elongated hole, and a longitudinal direction of the lower elongated hole is parallel to the XZ plane. . 10. The direct injection internal combustion engine according to claim 8, wherein the fuel injection ports on both sides are formed obliquely so that the fuel to be injected does not cross. 11. An in-cylinder injection type internal combustion engine having an ignition plug and injecting fuel directly into a cylinder by a fuel injection valve, wherein the cylinder center axis of the internal combustion engine intersects perpendicularly with the Z axis and the cylinder center of gravity. When the axis passing through the point directly below the position where the fuel injection valve is located is defined as the X axis, and the axis passing through the center of gravity of the cylinder and perpendicular to the X axis and the Z axis is defined as the Y axis, the axis rotates around the Y axis in the cylinder. A first fuel injection port for forming a fuel spray in which a spray angle in a direction perpendicular to the XZ plane is smaller than a spray angle in a direction parallel to the XZ plane. And a second fuel injection port for forming a fuel spray in which a spray angle in a direction perpendicular to the XZ plane is wider than a spray angle in a direction parallel to the XZ plane. Select the fuel injection port of Cylinder injection internal combustion engine, characterized in that it is set to select the second fuel injection port. 12. An isosceles triangle having an angle θ is assumed, and the angle θ is defined assuming that a stroke length of a piston in the cylinder is a height H of the isosceles triangle and a base length is L. It is an angle at which the total injected fuel amount can form an air-fuel mixture having a stoichiometric mixture ratio in an in-cylinder virtual rectangular parallelepiped having a cylinder inner diameter D × L × stroke length H.
The direct injection internal combustion engine according to any one of claims 1 to 11, wherein? Is a fuel spray angle in a direction perpendicular to the XZ plane. 13. The fuel injection valve can switch a fuel flow path in the injection valve main body by changing a valve lift amount, and when the valve lift amount is controlled to be small, the fuel injection valve operates during the low and medium load operation. 8. A fuel flow path connected to a fuel injection port to be used is selected, and when the valve lift is controlled to be large, a fuel flow path connected to the fuel injection port to be used during the high-load operation is set. 12. The direct injection internal combustion engine according to any one of claims 11 to 11.