JP2005098120A - Spark-ignition direct-injection engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve homogenization by restraining a collision of fuel with intake valves in homogeneous combustion, while maintaining ignitability in stratified combustion. <P>SOLUTION: The injection direction of the fuel injected from a fuel injection valve 18, is pointed to the electrode vicinity of a spark plug 16. The fuel injection valve 18 is provided with an electrode lower side nozzle port having the axis pointing to a space outside of a movable range of both intake valves 12, and in close vicinity to an under surface of an electrode of the spark plug 16, when looking at the tip side in the fuel injection direction from at least the fuel injection valve side, and an electrode under side nozzle port having the axis pointing a space in the movable range of both intake valves 12, and in close vicinity to the side of the electrode of the spark plug 16, when looking at the tip side in the fuel injection direction from the fuel injection valve side. The electrode lower side nozzle port is set so as to be positioned above a shade part upper surface of the intake valves 12 in the middle of an intake stroke of increasing a lift quantity of the intake valves 12. A fuel injection timing control means for setting the fuel injection timing, is constituted so that the fuel injection timing in the homogeneous combustion is set in the middle of the intake stroke. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a spark ignition direct injection engine, and more particularly to a spark ignition direct injection engine provided with a fuel injection valve having a plurality of injection holes.

2. Description of the Related Art Conventionally, a spark ignition direct injection engine is known that includes an ignition plug and an injector that directly supplies fuel into a combustion chamber so as to improve fuel efficiency by performing stratified combustion.
In this type of engine, it is required to promote vaporization and atomization while suppressing fuel diffusion, and to ensure that an air-fuel mixture having an appropriate air-fuel ratio that can be ignited in the vicinity of the electrode of the spark plug is unevenly distributed. .
As such a technique, for example, as disclosed in Patent Document 1 below, fuel is directly injected into the electrode of the spark plug, and an air flow is generated below or near the side of the spray, thereby spreading the spray. Technology to suppress is known.
JP 2001-248443 A

  However, in the above-mentioned Patent Document 1, since the fuel is directly injected toward the electrode, there is a problem that the fuel is likely to adhere to the electrode as droplets and the ignitability is deteriorated.

By the way, as disclosed in Patent Document 2 below, an injector having a plurality of injection holes (hereinafter referred to as a multi-hole type injector) is known.
Japanese Patent Laid-Open No. 2002-130082

Therefore, according to the present inventors, by using this multi-hole type injector, it is possible to collect an air-fuel mixture having an appropriate air-fuel ratio that can be ignited in the vicinity of the electrode while suppressing the adhesion of fuel to the electrode of the spark plug. Found that it would be possible.
In other words, instead of directly injecting fuel into the electrode, the fuel is injected from the plurality of nozzles by positioning the plurality of nozzles so that the fuel is unevenly distributed around the electrode. Since the atomization is achieved and the distribution center of the spray sprayed from each nozzle is located at a position avoiding the electrode of the spark plug, the amount of fuel dropletized and adhering to the electrode can be reduced. is there.

By the way, the spark ignition direct injection engine is configured to perform uniform combustion in addition to the above-described stratified combustion. During this uniform combustion, an air-fuel mixture is introduced near the electrode of the spark plug as in stratified combustion. Instead of collecting, it is necessary to disperse the air-fuel mixture throughout the combustion chamber to make the air-fuel mixture uniform.
However, when the multi-hole type injector described above is used, the injection nozzle is arranged so that the fuel spray is directed near the electrode of the spark plug during stratified combustion, so that the fuel spray is placed on the umbrella portion of the intake valve during uniform combustion. There is a possibility that the fuel cannot be sufficiently distributed in the combustion chamber on the side opposite to the fuel injection valve arrangement side due to collision and reflection of the fuel upward in the combustion chamber.

  The present invention has been made in consideration of the above problems, and its object is to maintain the ignitability during stratified combustion while suppressing the collision of fuel with the intake valve during uniform combustion. It is an object of the present invention to provide a spark ignition direct injection engine capable of improving the uniformity of the engine.

In order to achieve the above object, the present invention provides the following solution as a solution. That is, in the first configuration of the present invention, an ignition plug disposed in the combustion chamber, and a fuel injection valve disposed such that the tip portion faces the periphery of the combustion chamber between the two intake valves. A spark ignition direct injection engine in which the fuel injection direction injected from the fuel injection valve is directed to the vicinity of the electrode of the spark plug;
The fuel injection valve is oriented at least in a space in which the axial center is outside the movable range of the two intake valves and close to the lower surface of the electrode of the spark plug when viewed from the fuel injection valve side toward the front end side of the fuel injection direction. When viewed from the fuel injection valve side and the front end side of the fuel injection direction from the fuel injection valve side, the axis is directed to a space close to the side of the electrode of the spark plug within the movable range of the two intake valves. And an electrode side nozzle hole,
The axis of the electrode side nozzle hole is set so as to be positioned above the upper surface of the umbrella portion of the intake valve in the middle of the intake stroke in which the lift amount of the intake valve is large, and the fuel injected from the fuel injection valve Fuel injection timing control means for setting the injection timing according to the operating state of the engine,
The fuel injection timing control means is configured to set the fuel injection timing at the time of uniform combustion to the middle stage of the intake stroke.
According to the first configuration of the present invention, the electrode lower side nozzle hole is disposed outside the movable range of the intake valve, and the axis of the electrode side nozzle hole is above the upper surface of the intake valve umbrella portion in the middle of the intake stroke. Since the fuel injection timing is set to the middle stage of the intake stroke, the fuel injected from the lower electrode nozzle is prevented from colliding with the intake valve during uniform combustion, and the side of the electrode The fuel injected from the nozzle is also injected in the middle of the intake stroke, the axial center of which is located above the upper surface of the intake valve umbrella, so that collision with the intake valve is suppressed.
Furthermore, since the fuel is injected in the middle of the intake stroke where the intake flow velocity is fast, the fuel and air are effectively mixed, and the mixture can be made more uniform.
Accordingly, it is possible to improve the homogenization of the air-fuel mixture during the uniform combustion.
Further, at the time of stratified combustion, the atomized fuel is collected in the vicinity of the electrode of the spark plug by the electrode lower side nozzle hole and the electrode side side nozzle hole, so that the ignitability can be improved.

In the second configuration of the present invention, two electrode side nozzle holes are provided so as to be located in spaces on both sides of the electrode of the spark plug, respectively, and the electrode lower nozzle hole and the two electrode side nozzle holes are It is configured to be arranged in a substantially triangular shape centering on the electrode of the spark plug as viewed from the front end side in the fuel injection direction centering on the axis of the fuel injection valve.
According to the second configuration of the present invention, since the electrode of the spark plug is surrounded by the fuel spray injected from the three nozzles, the atomized mixture is sufficiently collected near the electrode of the spark plug during stratified combustion. And ignitability can be improved.

In the third configuration of the present invention, the outer peripheral edge of the fuel spray injected from the electrode side injection port is set substantially parallel to the combustion chamber ceiling wall on the intake valve side.
Here, in order to suppress the collision of the fuel injected from the electrode side injection port with the intake valve, the electrode side injection port is positioned as far as possible above the upper surface of the umbrella portion of the intake valve. Although it is desirable to cause the fuel spray to collide with the ceiling wall of the combustion chamber, the fuel spray may collide with the ceiling wall of the combustion chamber.
According to the third configuration of the present invention, since the fuel spray injected from the electrode side injection port is set substantially parallel to the combustion chamber ceiling wall on the intake valve side, the fuel spray is injected from the electrode side injection port. It is possible to prevent the fuel spray from colliding with the ceiling wall side of the combustion chamber.

In the fourth configuration of the present invention, an opening angle between the axial centers of the electrode lower side nozzle hole and the electrode side side nozzle hole is set in a range of 15 to 25 °.
As a result of diligent research by the present inventors, if the opening angle between the axial centers of each nozzle hole is in the range of 15 to 25 °, the appropriate mutual interference effect is suppressed while suppressing the mutual interference effect from becoming excessively large. It was confirmed that
In other words, if the opening angle is too small, the air volume between the fuel sprays is small, the mutual interference effect acts more and the spray penetration force becomes excessively large, and the injected fuel spray moves near the electrode of the spark plug. The problem arises that it passes through and cannot be collected near the electrode of the spark plug.
On the other hand, if the opening angle is too large, there is a problem that the fuel sprays are too far apart to obtain a mutual interference effect.
And according to the present inventors, it was confirmed by analysis and experiment that the opening angle at which these problems do not occur is 15 ° to 25 °.
According to the 4th structure of this invention, since the opening angle between the axial centers of both nozzle holes is set between 15-25 degrees, it is suitable, suppressing that a mutual interference effect becomes large too much. Since a mutual interference effect is obtained, the ignitability can be improved.

In the fifth configuration of the present invention, the axial center of the electrode side nozzle hole is seen from the upper edge of the piston at the piston position at the top dead center of the intake stroke when viewed from the fuel injection valve side toward the front end side in the fuel injection direction. It is configured to be positioned above.
According to the fifth configuration of the present invention, during the intake stroke injection, the axis of the electrode side nozzle hole is positioned above the upper edge of the piston, so that the fuel spray injected from the electrode side nozzle is the upper part of the piston. It is possible to suppress the collision.

  ADVANTAGE OF THE INVENTION According to this invention, the collision of the fuel to the intake valve at the time of uniform combustion can be suppressed, and the uniformity of air-fuel mixture can be improved, maintaining the ignitability at the time of stratified combustion.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is an overall configuration diagram of a spark ignition direct injection engine 1 according to an embodiment of the present invention.
The engine 1 is arranged on a cylinder block 3 in which a plurality of cylinders, for example, four cylinders 2, 2, 2, 2 (only one is disclosed in FIG. 1) are provided in series, and the cylinder block 3. A cylinder head 4 is provided, and a piston 5 is fitted in each cylinder 2 so as to reciprocate in the vertical direction. Combustion chambers 6 are divided in the cylinders 2 between the pistons 5 and the cylinder heads 4, and the combustion chambers 6 are substantially arranged at the ceiling of the cylinders 2 as shown in an enlarged view in FIG. 2. By forming two inclined surfaces extending from the central portion to the vicinity of the lower end surface of the cylinder head 4, a so-called pent roof type combustion chamber having a roof-like shape is formed. On the other hand, a crankshaft 7 is rotatably supported in the cylinder block 3 below the piston 5, and the crankshaft 7 and the piston 5 are connected via a connecting rod 8.

  As shown in FIGS. 1 and 2, the cylinder head 4 is formed with two intake ports 10 and two exhaust ports 11 (only one is disclosed in FIGS. 1 and 2). One end of each of the two intake ports 10 and 10 is opened to the combustion chamber 6 from one of the inclined surfaces in the ceiling portion of each cylinder 2, and the other end side of the two intake ports 10 and 10 extends obliquely upward from the combustion chamber 6. Inlet valves 12 and 12 that are opened and closed at a predetermined timing are respectively opened at one side surface (the right side surface in FIGS. 1 and 2) independently of each other, and at one end openings of the intake ports 10 and 10, respectively. Is arranged. (In FIG. 1 and FIG. 2, only one is disclosed.) Each of the two exhaust ports 11 and 11 has one end opened to the combustion chamber 6 from the other inclined surface in the ceiling portion of each cylinder 2, The other end side merges into one in the middle and then extends substantially horizontally and opens to the other end surface of the engine 1 (the left side surface in FIGS. 1 and 2). Exhaust valves 13 and 13 that are opened and closed at predetermined timings are arranged. (In FIG. 1 and FIG. 2, only one is disclosed)

  As shown in FIG. 1, an intake passage 30 that communicates with the intake ports 10 and 10 of each cylinder 2 is connected to one side of the engine 1. The intake passage 30 is for supplying intake air filtered by an air cleaner (not shown) to the combustion chamber 6 of the engine 1 and is sucked into the engine 1 in order from the upstream side to the downstream side. A hot wire type air flow sensor 31 for detecting the amount of intake air to be detected, an electric throttle valve 32 for restricting the intake passage 26, and a surge tank 33 are provided. The electric throttle valve 32 is not mechanically connected to an accelerator pedal (not shown), and is opened and closed by being driven by an electric drive motor (not shown).

  Further, the intake passage 30 on the downstream side of the surge tank 33 is an independent passage branched for each cylinder 2, and the downstream end portion of each independent passage is further branched into two to each of the intake ports 10, 10 is communicated.

  In addition, an ignition plug 16 is disposed at the upper portion of the combustion chamber 6 substantially at the center of the combustion chamber 6 surrounded by the four intake and exhaust valves 12, 12, 13, and 13. The electrode at the tip of the spark plug 16 is located at a position protruding a predetermined distance from the ceiling of the combustion chamber 6, and an ignition circuit 17 is connected to the base end of the spark plug 16 for each cylinder 2. The ignition plug 16 is energized at a predetermined timing.

  In addition, a fuel injection valve 18 is disposed on the periphery of the combustion chamber 6 between the two intake ports 10 and 10 and below the intake ports 10 and 10. The fuel injection valve 18 is a multi-hole type fuel injection valve having a plurality of injection holes, specifically, eight injection holes. Each injection hole is ignited so that fuel spray injected from each injection hole will be described later. The fuel injection direction of the fuel injection valve 18 is set so as to be directed near the electrode of the plug 16 and above the piston 5.

A fuel distribution pipe 19 common to all the cylinders 2, 2, 2, 2 is connected to the base end portion of the fuel injection valve 18, and the fuel distribution pipe 19 has a high pressure supplied from the fuel supply system 20. Fuel is distributed and supplied to each cylinder 2. The fuel supply system 20 is configured, for example, as shown in FIG. 3, and the low-pressure fuel pump 23, the low-pressure regulator are arranged from the upstream side to the downstream side of the fuel passage 22 that communicates the fuel distribution pipe 19 and the fuel tank 21. 24, a fuel filter 25, a high-pressure fuel pump 26, and a high-pressure regulator 27 capable of adjusting the fuel pressure are sequentially arranged. The high-pressure fuel pump 26 and the high-pressure regulator 27 are connected to the fuel tank 21 side by a return passage 29. ing. Reference numeral 28 denotes a low pressure regulator that adjusts the pressure state of the fuel returned to the fuel tank 21 side.
The high-pressure fuel pump 26 is disposed on the end side of a cam shaft (not shown) and is configured to be driven according to the rotation of the cam shaft.

  Thus, the fuel sucked up from the fuel tank 21 by the low-pressure fuel pump 23 is regulated by the low-pressure regulator 24 and then pumped to the high-pressure fuel pump 26 via the fuel filter 25. A part of the fuel boosted by the high-pressure fuel pump 26 is returned to the fuel tank 21 side by the return passage 29 while adjusting the flow rate by the high-pressure regulator 27, so that the pressure state of the fuel supplied to the fuel distribution pipe 19 is an appropriate value, For example, the pressure is adjusted to 12 MPa to 20 MPa.

  On the other hand, as shown in FIG. 1, an exhaust passage 36 for discharging burned gas (exhaust gas) from the combustion chamber 6 is connected to the other side of the engine. An upstream end portion of the exhaust passage 36 is an exhaust manifold 37 that branches into each cylinder 2 and communicates with the exhaust port 11. A linear O 2 sensor that detects an oxygen concentration in the exhaust is provided at a collection portion of the exhaust manifold 37. 38 is disposed. The linear O2 sensor 38 is used to detect the air-fuel ratio based on the oxygen concentration in the exhaust gas, and can output linearly with respect to the oxygen concentration within a predetermined range including the theoretical air-fuel ratio. .

  Further, the upstream end of the exhaust pipe 39 is connected to the collecting portion of the exhaust manifold 37, and the three-way catalyst 54 and the NOx absorbent 40 are sequentially connected to the exhaust pipe 39 from the upstream side to the downstream side. It is connected. The NOx absorbent 40 absorbs NOx in an atmosphere with a high oxygen concentration in the exhaust, while releasing NOx absorbed as the oxygen concentration decreases, and reduces and purifies the released NOx by HC, CO, etc. in the exhaust. NOx absorption reduction type.

  In FIG. 1, reference numeral 50 denotes an engine control unit, which is an ignition circuit 17, a fuel injection valve 18, a high pressure regulator 27 for a fuel supply system 20, an electric throttle valve 32, an intake flow control valve (not shown), an EGR valve ( The engine control unit (hereinafter referred to as ECU) 50 is controlled. For this reason, at least the output signals from the crank angle sensor 9, the airflow sensor 31, the linear O2 sensor 38, etc., which detect the rotation angle (engine speed) of the crankshaft 7, are input to the ECU 50, in addition to the accelerator. An output signal from an accelerator opening sensor 51 that detects the opening of the pedal (accelerator operation amount) is input.

The ECU 50 performs fuel injection timing by the fuel injection valve 18, fuel pressure control by the high pressure regulator 27, and combustion state control by the fuel injection valve 18, the ignition circuit 17, and the high pressure regulator 27 based on signals input from the sensors. It is configured.
(Fuel injection control)
In the fuel injection control, the fuel injection control map is switched according to the engine temperature, and the control is performed according to the switched map.
The fuel injection control map is a warm time map shown in FIG. 4A when the engine temperature is a predetermined value (for example, 80 degrees) or more, and is shown when the engine temperature is lower than the predetermined value. The map is switched to the cold map shown in 4 (b).
As shown in FIG. 4A, the warm-time map is a stratified combustion region when the engine operating state is in the low load low rotation region, and in this region, the fuel injection timing by the fuel injection valve 18 is compressed. In the case of batch injection, for example, in the case of batch injection, fuel is injected in the range of 0 ° to 60 ° before compression top dead center (BTDC), and the mixture is burned in a state where the air-fuel mixture is unevenly distributed in the vicinity of the spark plug 16. Stratified combustion is performed. In this stratified combustion region, the fuel injection amount and the throttle opening are controlled so that the air-fuel ratio of the air-fuel mixture is leaner than the stoichiometric air-fuel ratio. Further, the region other than the stratified combustion region is a uniform combustion region, and the intake valve 12 in the middle of the intake stroke of the cylinder 2 by the fuel injection valve 18, for example, around 100 ° to 120 ° after the intake top dead center, is lifted to the maximum. Fuel is injected into the crank angle range of approximately the maximum lift at which the intake valve lifts 3/4 or more of the maximum lift amount, for example, within the crank angle range of 60 ° to 150 ° after the intake top dead center. Thus, the fuel is sufficiently mixed with the intake air to form a uniform air-fuel mixture in the combustion chamber 6, and the uniform combustion is performed. In this uniform combustion region, the fuel injection amount and the throttle opening are controlled so that the air-fuel ratio of the air-fuel mixture becomes substantially the stoichiometric air-fuel ratio (A / F≈14.7) in most operation regions. In the load operation state, the air-fuel ratio is controlled to be richer than the stoichiometric air-fuel ratio (A / F = about 13), and a large output corresponding to a high load can be obtained.
In the cold map, as shown in FIG. 4B, uniform combustion is performed in the entire operation region.

(Fuel pressure control)
In the fuel pressure control, the fuel pressure control map is switched according to the engine temperature, and the control is performed according to the switched map.
The fuel pressure control map is a warm time map shown in FIG. 5A when the engine temperature is a predetermined value (for example, 80 degrees) or more, and FIG. 5 when the engine temperature is lower than the predetermined value. The map is switched to the cold map shown in (b).
As shown in FIG. 5A, the warm-time map shows that in the stratified combustion region, the fuel pressure is changed between 12 MPa and 20 MPa as the engine speed increases, but at least in the uniform combustion region on the high rotation side. , Uniformly set to 20 MPa.
Moreover, the map at the time of cold is uniformly set to 20 MPa in the entire operation region where uniform combustion is performed as shown in FIG.
However, as described above, the high-pressure fuel pump 26 is driven according to the rotation of the camshaft, and since the rotation of the camshaft is low and the fuel pressure does not rise sufficiently at the start, the fuel pressure at the start Is, for example, about 0.5 MPa.

Next, the eight injection holes of the multi-hole type fuel injection valve 18 which are the points of the present invention will be described with reference to FIGS. 2 and 6 to 9.
FIG. 6 is a diagram schematically showing a three-dimensional inclination angle with respect to the axis of each nozzle hole with respect to the axis when the front end side of the fuel injection direction is viewed around the axis of the multi-hole type fuel injection valve 18. 7 is a longitudinal sectional view of the cylinder head in which the piston is at the bottom dead center position, FIG. 8 is a view taken along the line AA in FIG. 7, and FIG. 9 is a view in which fuel is injected from each injection hole of the multi-hole type fuel injection valve 18. It is a perspective view which shows a state.

In FIG. 6, L is the axis of the multi-hole fuel injection valve 18, V is the maximum lift position of the intake valve 12 (for example, the position when the maximum lift is 9 mm), and P1 is the piston top dead center position. , P2 is the piston bottom dead center position, L1 to L8 are the axial centers of the first to eighth nozzles (the nozzles are not shown), and A1 to A8 are the spray angles of the fuel injected from the first to eighth nozzles. , E indicate the electrodes of the spark plug.
The nozzle diameters of all the nozzle holes are the same, for example, set to 0.15 mm.
Note that L1 corresponds to the axis of the electrode lower side nozzle hole in the claims, and L2 and L3 correspond to the axis of the electrode side nozzle hole in the claims.
The axis L1 to L8 of each nozzle hole is as follows with respect to the axis L, the maximum lift position V of the intake valve, the piston top dead center position P1, the piston bottom dead center position P2, and the electrode E of the spark plug. The inclination angle is related.

First, the axis L1 of the first nozzle hole is arranged so as to be directed from the axis L to a predetermined position below the electrode E of the spark plug. Note that the axis L1 and the spray angle A1 of the first nozzle are located between the maximum lift positions V of the two intake valves 12, that is, outside the movable range of the intake valve 12.
Further, the spray angle A1 of the fuel injected from the first nozzle is arranged so as to be positioned between the intake valves 12 and 12, as shown in FIG.
The axis L2 of the second nozzle hole is arranged so as to be directed from the axis L to a predetermined position on the side of the electrode E of the spark plug (left side in the figure).
The axial center L3 of the third nozzle hole is arranged so as to be directed from the axial center L to a predetermined position on the side of the electrode E of the spark plug (right side in the figure).
The axis L2 of the second nozzle hole, the spray angle A2, the axis L3 of the third nozzle hole, and the spray angle A3 are all located within the movable range of the maximum lift positions V, V of the intake valve 12.
Further, as shown in FIG. 8, the spray angle A2 of the second nozzle hole and the spray angle A3 of the third nozzle hole are positioned above the intake valves 12 and 12 in the middle of the intake stroke when the lift amount of the intake valve becomes large. In addition, as shown in FIG. 7, the outer peripheral edge is set to be substantially parallel to the intake side ceiling wall 6 a of the combustion chamber 6.
In addition, the shaft centers L1 to L3 and the spray angles A1 to A3 of the first nozzle hole to the third nozzle hole are the top dead center positions (indicated by two-dot chain lines in FIG. 8), as shown in FIG. However, it is set to be positioned above the upper edge of the piston.

The axial center L4 of the fourth nozzle hole is arranged so as to be directed from the axial center L to a predetermined position (left side in the figure) above the piston bottom dead center position P2 on the piston side (lower side in the figure).
The axis L5 of the fifth nozzle hole is arranged on the piston side (lower side in the figure) from the axis L so as to be directed to a predetermined position (center position in the figure) above the piston bottom dead center position P2. .
The axis L6 of the sixth nozzle hole is arranged so as to be directed from the axis L to a predetermined position (right side in the figure) above the piston bottom dead center position P2 on the piston side (lower side in the figure).
The shaft center L7 of the seventh nozzle hole is arranged so as to be directed from the shaft center L to a predetermined position (left side in the figure) below the piston bottom dead center position P2 on the piston side (lower side in the figure).
The axial center L8 of the eighth nozzle hole is disposed so as to be directed from the axial center L to a predetermined position (right side in the figure) below the piston bottom dead center position P2 on the piston side (lower side in the figure).
The axis L3 to L8 and the spray angles A3 to A8 of the third to eighth nozzles are located outside the movable range of the maximum lift positions V and V of the intake valve 12, respectively.
Further, the entire fuel spray injected from each nozzle is set so as to be within a conical space of 70 ° or less with the axis L as the center.
Then, as described above, the spray of fuel injected from the fuel injection valve 18 in which each nozzle hole and spray angle are set is in a state as shown in FIG. 9, for example.

As described above, since the axial centers L1 to L3 of the first to third nozzle holes are disposed below and on both sides of the electrode E of the spark plug, atomization occurs near the electrode E of the spark plug during stratified combustion. The collected air-fuel mixture can be collected, and the ignitability can be improved.
Further, the spray angle A2 of the second nozzle hole and the spray angle A3 of the third nozzle hole are positioned above the intake valves 12 and 12 in the middle of the intake stroke when the lift amount of the intake valve becomes large. The collision of the fuel spray injected from the injection port with the intake valves 12, 12 can be suppressed.
In addition, since the outer peripheral edges of the spray angle A2 of the second nozzle hole and the spray angle A3 of the third nozzle hole are set to be substantially parallel to the intake side ceiling wall 6a of the combustion chamber 6, the second and third nozzle holes Collision of the injected fuel spray on the ceiling wall 6a can be suppressed.
Further, the axial centers L1 to L3 and the spray angles A1 to A3 of the first to third nozzle holes are set so as to be positioned above the upper edge of the piston even when the piston is at the top dead center position. The collision of the fuel spray injected from the first to third nozzle holes with the piston 5 can be suppressed.
Further, since the shaft centers L4 to L8 of the fourth to eighth nozzle holes are arranged on the piston side with respect to the shaft center L, the air-fuel mixture can exist in the entire combustion chamber 6, and the air-fuel mixture at the time of uniform combustion can be made. Homogenization can be improved.
Further, since the axial centers L1, L4 to L8 of the first, fourth to eighth nozzles are arranged outside the movable range of the intake valve 12, most of the nozzle holes are movable within the movable range of the intake valve 12 while being multi-holes. It can arrange | position outside and it can suppress that the fuel spray injected from each nozzle hole collides with the intake valve 12. FIG.

Here, regarding the relationship with the first nozzle hole L1 to the third nozzle hole L3 disposed in the vicinity of the electrode E of the spark plug, there are the following requirements.
In other words, when the stratified charge combustion is warm, the atomized air-fuel mixture is collected in the vicinity of the electrode E of the spark plug, so that it is necessary to generate a mutual interference effect. When this occurs, a rich air-fuel mixture adheres to the electrode of the spark plug and the startability deteriorates, so there is a demand for preventing the mutual interference effect from occurring.
Therefore, the axial centers L1 to L3 of the first to third nozzle holes whose axial centers are directed around the electrode E of the spark plug are the spray angle α of the fuel injected from each nozzle hole, and the opening angle θ of each nozzle hole. Is set to have the following relationship.
The opening angle θ is set in advance to an angle between 15 ° and 25 °, for example, 20 °. The spray angle α varies depending on the difference in fuel pressure and in-cylinder pressure, and the spray angle α is different from the opening angle θ. Relationships are changing.
First, when the stratified charge combustion is warm, for example, when the fuel pressure is 12 MPa and the in-cylinder pressure is 1 MPa, as shown in FIG. 10A, injection is performed from the first injection port and the second injection port (third injection port). The fuel spray angle α1 is widened and is larger than the opening angle θ1 between the first nozzle hole and the second nozzle hole (third nozzle hole).
Accordingly, the spray angles α1 are close to each other, and a mutual interference effect is generated between the fuel sprays injected from the first nozzle hole and the second nozzle hole and from the first nozzle hole and the third nozzle hole.
The reason why the warm spray angle α1 is increased is that both the fuel pressure and the in-cylinder pressure are high and the friction between the fuel and the in-cylinder air is large, so that the fuel is vaporized and the vaporized fuel spreads outward.
Further, at the time of cold start in which uniform combustion is performed, for example, when the fuel pressure is 0.5 MPa and the in-cylinder pressure is 0.1 MPa, as shown in FIG. The spray angle α2 of the fuel injected from the three nozzle holes is small, and the angle is smaller than the opening angle θ1 between the first nozzle hole and the second nozzle hole (third nozzle hole).
Accordingly, the spray angles α2 are positioned away from each other, and the above-described mutual interference effect is not generated.
The reason why the spray angle α2 during the cold start is small is that both the fuel pressure and the in-cylinder pressure are low, the friction between the fuel and the in-cylinder air is small, the fuel is poorly vaporized, and the outward spread of the fuel is small. It is.

Moreover, there exists the following request | requirement about the relationship between the axial center L1 of a 1st nozzle hole, and the axial center L5 of the 5th nozzle hole arrange | positioned below the axial center L1 of the 1st nozzle hole.
That is, in order to ensure the ignitability during stratified combustion, the axis L1 of the first nozzle hole needs to be directed to the vicinity of the electrode E of the spark plug, but the fifth nozzle approaches the first nozzle hole. If it passes, a mutual interference effect will arise between the 1st nozzle hole and the 5th nozzle hole, the fuel spray injected from the 1st nozzle hole will be drawn to the 5th nozzle side, and air-fuel mixture will be collected in the vicinity of electrode E of a spark plug There is a risk that it will not be possible.
Therefore, the axis L1 of the first nozzle hole and the axis L5 of the fifth nozzle hole have a relationship such that the spray angle α of the fuel injected from each nozzle hole and the opening angle θ of each nozzle hole are as shown below. Is set.
The opening angle θ is preset to, for example, approximately 35 °, and the spray angle α changes depending on the difference in fuel pressure and in-cylinder pressure, and the relationship between the spray angle α and the opening angle θ changes. Yes.
First, when the stratified charge combustion is warm, for example, when the fuel pressure is 12 MPa and the in-cylinder pressure is 1 MPa, as shown in FIG. 11A, the fuel spray injected from the first and fifth nozzles Although the angle α3 widens, the angle is smaller than the opening angle θ2 between the first nozzle hole and the fifth nozzle hole.
Accordingly, the spray angles α3 are located away from each other and do not cause a mutual interference effect.
Further, at the time of cold start in which uniform combustion is performed, for example, when the fuel pressure is 0.5 MPa and the in-cylinder pressure is 0.1 MPa, as shown in FIG. 11 (b), injection is performed from the first injection port and the fifth injection port. The spray angle α4 of the fuel spray is further reduced with respect to the warm time, and the cold spray angle α4 is smaller than the opening angle θ2 between the first and fifth nozzles in the cold state as in the warm time. Yes.
Accordingly, the spray angles α4 are located away from each other and no mutual interference effect occurs.
As described above, the first nozzle hole and the fifth nozzle hole are fuels injected from the respective nozzle holes so that the mutual interference effect does not occur both in the warm time in which stratified combustion is performed and in the cold start in which uniform combustion is performed. The relationship between the spray angle and the opening angle between the nozzle holes is set.

Here, the reason why the opening angle θ1 is set between 15 ° and 25 ° is as follows.
That is, if the opening angle θ is too small, the air volume between the fuel sprays is small, the mutual interference effect acts more, and the spray penetration force L becomes excessively large. There arises a problem that it passes through the vicinity of the electrode E and cannot be collected in the vicinity of the electrode E of the spark plug 16.
On the other hand, if the opening angle θ is too large, there is a problem that the fuel sprays are too far apart to obtain a mutual interference effect.
Then, it was confirmed by analysis and experiment that the opening angle θ at which these problems do not occur is 15 ° to 25 ° when the nozzle diameter of the fuel injection valve 18 is 0.15 mm and the fuel pressure is 20 MPa.

The distance from the first through third nozzle holes to the electrode E of the spark plug 16 is set to 20 mm or more.
Hereinafter, the reason will be described with reference to FIG.
First, the fuel spray injected from the nozzle is present in the vicinity of the center, a central spray region a in which liquid fuel that is not atomized is distributed, and the atomized fuel that exists outside the center spray region a. Can be divided into the peripheral spray region b in which is distributed.
Normally, the fuel spray injected from the nozzle hole gradually spreads conically from the nozzle hole, but if the peripheral spray region b is shorter than 20 mm from the nozzle hole, atomization has not progressed and is not present. .
On the other hand, the spark plug 16 is disposed in the peripheral spray region b outside the central spray region a because the electrode E of the spark plug 16 is wet and does not ignite when disposed in the central spray region a in each spray region. There is a need.
From the above, it is necessary to arrange the spark plug 16 in the peripheral spray region b that is 20 mm or more away from the nozzle hole.

Here, the definitions of the spray angle α and the spray penetration force L described above will be described with reference to FIG.
The spray angle α is a geometric fuel injection area from the fuel injection valve 18, and the geometric fuel injection area is a fuel spray when there is no intake flow in the combustion chamber 6. This is the droplet area.
Hereinafter, specific examples will be described.
As shown in FIG. 13 (a), at a position 20 mm downstream from the nozzle part A point of the fuel injection valve 18, two points B and C where the imaginary plane through which the spray center line passes and the outline of the fuel spray intersect are determined. The spray angle α is defined by ∠BAC (α = ∠BAC).
Further, as shown in FIG. 13 (b), the distance from the most advanced portion of the spray is defined as the spray penetration force L with respect to the axial direction of the fuel injection valve 18.
As an actual measurement method of the spray angle α and the spray penetration force L, for example, a laser sheet method may be used.
That is, first, a sample of dry sol belt corresponding to fuel properties is used as the fluid injected by the fuel injection valve 18, and the pressure of this sample is set to a predetermined value within the range of fuel pressure actually used at room temperature (for example, 12 MPa). Moreover, as an atmospheric pressure, the pressure vessel provided with the laser passage window which can image | photograph spraying, and the window for a measurement is pressurized to 0.5 Mpa, for example. Then, a drive pulse signal having a predetermined pulse width is input to the fuel injection valve 18 so that the fuel injection amount per pulse is 9 mm ³ / stroke at room temperature, and fuel is injected. At this time, a laser sheet light having a thickness of 5 mm is irradiated to the fuel spray so as to pass through the spray center line, and a spray image is taken with a high-speed camera from a direction orthogonal to the laser sheet light surface. Take a picture. Then, the spray angle θ and the spray penetration force L are determined according to the above-mentioned definition based on the imaging screen 1.56 milliseconds after the input timing of the above-described drive pulse signal.
Note that the spray contour in the photographed image is the contour of the droplet-shaped sample particle area, and the sample particle area is brightened by the laser sheet light. I try to figure out the outline.

Therefore, according to the present embodiment, when warm, both the fuel pressure and the in-cylinder pressure are high and the spray angle α is likely to spread, and the axis L1 of the first injection port and the axis L2 of the second injection port of the fuel injection valve 18 are maintained. And the opening angle θ between the axis L1 of the first nozzle hole and the axis L3 of the third nozzle hole are set to be equal to or less than the spray angle α of the fuel injected from both the nozzle holes, respectively. The air volume in the space between the spray angles α of fuel injected from the first nozzle hole and the second nozzle hole, and the air volume in the space between the spray angles α of fuel injected from the first nozzle and the third nozzle, respectively. And the mutual interference effect of each fuel spray described above can be obtained, so that the ignitability can be improved.
Further, when cold, both the fuel pressure and the in-cylinder pressure are low, and the spray angle α is difficult to spread, and the opening angle is made larger than the spray angle α. Therefore, the fuel is injected from the first and second nozzles. Since the air volume in the space between the sprayed angles α and the air volume in the space between the spray angles α ejected from the first and third nozzles can be increased and the above-described mutual interference effect can be suppressed, atomization can be achieved. It can suppress that the air-fuel | gaseous mixture which adhered to the electrode E in large quantities, and ignitability deteriorates.
Further, the axis L2 of the second nozzle hole, the spray angle A2, the axis L3 of the third nozzle hole, and the spray angle A3 are positioned above the intake valves 12 and 12 in the middle of the intake stroke when the lift amount of the intake valve increases. Therefore, it is possible to suppress the collision of the fuel spray injected from the second and third nozzles with the intake valves 12 and 12 in the middle of the intake stroke.
Further, since the outer peripheral edges of the spray angle A2 of the second nozzle hole and the spray angle A3 of the third nozzle hole are set so as to be substantially parallel to the intake side ceiling wall 6a of the combustion chamber 6, injection is performed from the second and third nozzle holes. The collision of the fuel spray applied to the ceiling wall 6a can be suppressed.
Further, the axial centers L1 to L3 and the spray angles A1 to A3 of the first to third nozzle holes are set so as to be positioned above the upper edge of the piston even when the piston 5 is at the top dead center position. Therefore, the collision of the fuel spray injected from the first to third nozzle holes with the piston 5 can be suppressed.
Further, the opening angle θ between the axis L1 of the first nozzle hole and the axis L2 of the second nozzle hole, and the opening angle θ between the axis L1 of the first nozzle hole and the axis L3 of the third nozzle hole are 15 to 25 °. Therefore, the appropriate mutual interference effect can be obtained while suppressing the mutual interference effect from becoming excessively large, so that the ignitability can be improved.
In addition, since the distance from the first to third nozzle holes to the electrode E of the spark plug 16 is set to 20 mm or more, a mutual interference effect can be reliably obtained, ignitability can be improved, and atomization can be achieved. The electrode E of the spark plug 16 can be disposed in the peripheral spray region b where the dispersed fuel is distributed, and the fuel that has not been atomized can be prevented from adhering to the electrode E.
Further, at the time of stratified combustion, the opening angle θ between the axis L1 of the first nozzle hole and the axis L5 of the fifth nozzle hole is made larger than the spray angle α of the fuel injected from both the nozzle holes. Since the air volume in the space between the spray angles α injected from the nozzle holes is expanded and the mutual interference of the fuel sprays described above can be suppressed, the fuel spray injected from the first nozzle holes is attracted to the fifth nozzle side. The air-fuel mixture can be collected near the electrode E of the spark plug 16.
Further, since fuel is injected from the fourth to eighth nozzles arranged on the piston side during uniform combustion, the air-fuel mixture can be dispersed throughout the combustion chamber, and the air-fuel mixture in the combustion chamber 6 can be made uniform. Can be planned.
In addition, during uniform combustion, fuel is injected in the middle of the intake stroke where the intake air flow rate is fast, so that mixing of the fuel and air is effectively performed, and the mixture can be made more uniform.

  In this embodiment, an example of the multi-hole type fuel injection valve 18 having eight injection holes is shown. However, the present invention may be applied to a multi-hole type fuel injection valve having other numbers of injection holes. .

1 is an overall configuration diagram of a spark ignition direct injection engine according to an embodiment of the present invention. The cylinder head longitudinal cross-sectional view which concerns on embodiment of this invention. 1 is a schematic diagram of a fuel supply system according to an embodiment of the present invention. (A) is a figure which shows the fuel-injection control map at the time of warm which concerns on embodiment of this invention, and is a figure which shows the fuel-injection control map at the time of cold. (A) is a figure which shows the fuel pressure control map at the time of warm which concerns on embodiment of this invention, (b) is a figure which shows the fuel pressure control map at the time of cold. The figure which shows typically the three-dimensional inclination | tilt angle with each nozzle hole with respect to an axial center when the fuel injection direction front end side is seen centering on the axial center of the fuel injection valve which concerns on embodiment of this invention. The longitudinal cross-sectional view of the cylinder head in the piston bottom dead center position which concerns on embodiment of this invention. FIG. 9 is an AA arrow view of FIG. 8. The perspective view which shows the fuel-injection state from the fuel injection valve which concerns on embodiment of this invention. (A) is a figure which shows the relationship between the spray angle of the fuel at the time of the warm time which concerns on embodiment of this invention, and the opening angle of a 1st nozzle hole, and a 2nd, 3rd nozzle hole, (b) is the time of a cold start The figure which shows the relationship between the spray angle of a fuel, and the opening angle of a 1st nozzle hole, and a 2nd, 3rd nozzle hole. (A) is a figure which shows the relationship between the spray angle of the fuel at the time of warm which concerns on embodiment of this invention, and the opening angle of a 1st nozzle hole, and a 5th nozzle hole, (b) is the fuel atomization at the time of cold start The figure which shows the relationship between an angle | corner and the opening angle of a 1st nozzle hole and a 5th nozzle hole. The figure which shows the spraying state of the fuel spray which concerns on embodiment of this invention. Explanatory drawing explaining the definition of the spray angle which concerns on embodiment of this invention, and the spray penetration force.

Explanation of symbols

1: engine 6: combustion chamber 6a: ceiling wall 12, 12: intake valve 16: ignition plug 18: fuel injection valve 23: low pressure fuel pump (fuel pressure adjusting means)
24: Low pressure regulator (fuel pressure adjustment means)
26: High-pressure fuel pump (fuel pressure adjusting means)
27: High pressure regulator (fuel pressure adjustment means)
50: Engine control unit (fuel injection timing control means)
V: Maximum lift position of intake valve (movable range of intake valve)
L: Axis center L1: Axis line of first nozzle hole (axis center of electrode lower nozzle hole)
L2: Axis of second nozzle hole (axis of electrode side nozzle hole)
L3: Axis of third nozzle hole (axis of electrode side nozzle hole)
α1, α2, α3, α4: Spray angle θ1, θ2: Opening angle

Claims (5)

A fuel to be injected from the fuel injection valve, comprising: a spark plug disposed in the combustion chamber; and a fuel injection valve disposed such that a tip portion thereof faces the periphery of the combustion chamber between the two intake valves. In the spark ignition direct injection engine in which the injection direction is directed to the vicinity of the electrode of the spark plug,
The fuel injection valve is oriented at least in a space in which the axial center is outside the movable range of the two intake valves and close to the lower surface of the electrode of the spark plug when viewed from the fuel injection valve side toward the front end side of the fuel injection direction. When viewed from the fuel injection valve side and the front end side of the fuel injection direction from the fuel injection valve side, the axis is directed to a space close to the side of the electrode of the spark plug within the movable range of the two intake valves. And an electrode side nozzle hole,
The axis of the electrode side nozzle hole is set so as to be positioned above the upper surface of the umbrella portion of the intake valve in the middle of the intake stroke in which the lift amount of the intake valve is large, and the fuel injected from the fuel injection valve Fuel injection timing control means for setting the injection timing according to the operating state of the engine,
The spark ignition direct injection engine characterized in that the fuel injection timing control means is configured to set the fuel injection timing at the time of uniform combustion in the middle of the intake stroke. Two electrode side nozzle holes are provided so as to be located in spaces on both sides of the electrode of the spark plug,
The electrode lower side nozzle hole and the two electrode side side nozzle holes are arranged in a substantially triangular shape centering on the electrode of the spark plug when viewed from the front end side in the fuel injection direction centering on the axis of the fuel injection valve. 2. The spark ignition direct injection engine according to claim 1, wherein   3. The spark ignition direct type according to claim 1, wherein an outer peripheral edge of the fuel spray injected from the electrode side nozzle hole is set substantially parallel to a combustion chamber ceiling wall on the intake valve side. Jet engine.   The opening angle between the axial centers of the electrode lower side nozzle hole and the electrode side side nozzle hole is set within a range of 15 to 25 °. Spark ignition direct injection engine.   The axial center of the electrode side nozzle hole is located above the upper edge of the piston at the piston position at the top dead center of the intake stroke when viewed from the fuel injection valve side toward the front end side in the fuel injection direction. Features a spark ignition direct injection engine.

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