JP4103754B2 - Spark ignition direct injection engine - Google Patents

Description

  The present invention relates to a spark ignition direct injection engine, and more particularly to a spark ignition direct injection engine including 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.
However, in Japanese Patent Application Laid-Open No. 2001-248443, since the fuel is directly injected toward the electrode, there is a problem that the fuel tends to adhere to the electrode as droplets and the ignitability deteriorates.

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.
JP, 2002-130082, A Therefore, according to the present inventors, by using this multi-hole type injector, while suppressing the adhesion of fuel to the electrode of the spark plug, it is possible to ignite in the vicinity of the electrode. It has been found that it becomes possible to collect an air-fuel mixture at a fuel ratio.

  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, in order to improve the ignitability in the stratified combustion described above, not only the air-fuel mixture is collected in the vicinity of the spark plug electrode, but also how the air-fuel mixture can stay in the vicinity of the spark plug electrode. Become important.

  That is, as described above, even if the injection hole is set so that the air-fuel mixture is collected near the electrode of the spark plug by the multi-hole type injector, if the fuel spray penetration force is too large, the fuel spray will move around the spark plug for a short time. It will not be possible to ensure ignitability.

  In order to allow the air-fuel mixture to stay in the vicinity of the spark plug electrode for a long time, the fuel spray penetration force can be reduced. However, simply by reducing the fuel spray penetration force, the fuel spray spreads quickly. As a result, the air-fuel mixture may not be collected near the electrode of the spark plug.

  The present invention has been made in consideration of the above problems, and its purpose is to collect an air-fuel mixture in the vicinity of the electrode of the spark plug during stratified combustion, and to ensure a long staying time for ignition. An object is to provide a spark ignition direct injection engine capable of improving the performance.

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 between the two intake valves so that the tip portion faces the peripheral edge of the combustion chamber are provided. In the 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 ignition plug, the fuel injection valve includes a plurality of fuel injection valves so as to be positioned in the vicinity of the electrode of the ignition plug. , Which are at least viewed from the fuel injection valve side toward the front end side in the fuel injection direction, and have an electrode lower side nozzle hole whose axial center is directed to a space close to the lower surface of the electrode of the spark plug, and an axial center Rutotomoni but such a the electrode lateral side injection port directed to the space adjacent to the side electrode of the spark plug, which both injection port watches jetting direction tip end side around the axis of the fuel injection valve, the Electrode lower side nozzle is above A fuel spray that is located outside the movable range of the intake valve, is set so that the electrode side nozzle holes are positioned within the movable range of both the intake valves, and fuel is injected from the electrode side nozzle holes. The force is configured to be smaller than the spray penetration force of the fuel injected from the electrode lower side nozzle hole .

According to the above-described configuration, the spray penetration force of the fuel injected from the plurality of nozzles is configured to be different from each other, so that a difference occurs in the time for the fuel spray injected from each nozzle to reach the vicinity of the spark plug electrode. As a result, the air-fuel mixture can exist in the vicinity of the electrode of the spark plug for a long time, and the ignitability during stratified combustion can be improved.

Spray penetration force of the fuel injected from the top Symbol each nozzle hole can be set by varying at least one of the injection bore or passage length of each nozzle hole.

The aforementioned fuel injection valve, comprising the electrode lower side nozzle hole directed to a space adjacent to the lower surface of the electrodes of the spark plug, the electrode lateral side injection port directed to the space adjacent to the side of the spark plug electrodes Therefore, the air-fuel mixture can be effectively collected around the electrode of the spark plug, and the ignitability during stratified combustion can be improved.

Further, in the above-described configuration, the spark ignition direct injection engine is provided with two intake valves, and a tip portion of the fuel injection valve is disposed between the two intake valves. The electrode lower side nozzle holes are located outside the movable range of the two intake valves, and the electrode side nozzle holes are the two intake valves. The fuel spray penetrating force injected from the electrode side nozzle hole is set smaller than the fuel spray penetrating force injected from the electrode lower nozzle hole. It is configured as follows.

  Here, it is desirable that each nozzle hole is disposed outside the movable range of the intake valve so as not to collide with the intake valve. However, in order to collect the air-fuel mixture near the electrode of the spark plug, when the nozzle holes are arranged below and to the side of the electrode of the spark plug, the nozzle holes arranged on the side of the electrode are located within the movable range of the intake valve, The fuel spray injected from the nozzle hole collides with the intake valve.

  Therefore, when the fuel spray penetration force is made different, if the fuel spray penetration force of the fuel injected from the nozzle arranged on the side of the electrode where the fuel spray collides with the intake valve is reduced, the fuel flow rate injected from the nozzle And the fuel spray colliding with the intake valve is reduced.

According to the above-described configuration, the spray penetration force of the fuel injected from the electrode side nozzle hole is set smaller than the spray penetration force of the fuel injected from the electrode lower nozzle hole. While suppressing the collision of fuel spray injected from the intake valve to the intake valve as much as possible, it is possible to obtain a time difference until the fuel spray injected from each nozzle reaches the vicinity of the spark plug electrode, and ignitability during stratified combustion Can be improved .

In the second configuration of the present invention, the axial center of the electrode side nozzle hole is set so as to be positioned above the umbrella portion of the intake valve in the middle of the intake stroke when the lift amount of the intake valve is large. A fuel injection timing control means for setting the fuel injection timing injected from the injection valve according to the operating state of the engine;
The fuel injection timing control means is configured to set the fuel injection timing during uniform combustion to the middle of the intake stroke where the lift amount of the intake valve is large.

According to the above configuration, the axial center of the electrode side nozzle hole is set in the middle of the intake stroke, and the fuel injection timing is set in the middle of the intake stroke, so that the fuel injected from the electrode side nozzle is during uniform combustion. Is prevented from colliding with the intake valve, reaching the vicinity of the electrode of the spark plug of the fuel spray injected from each nozzle while suppressing the collision of the fuel spray injected from the electrode side nozzle with the intake valve as much as possible. Thus, the time difference until the igniting can be obtained, and the ignitability during stratified combustion can be improved .

  According to the present invention, during stratified combustion, the air-fuel mixture can be collected in the vicinity of the electrode of the spark plug, the staying time can be secured long, and the ignitability can be improved.

  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. Has been placed. (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).

  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 intake port 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 to the vicinity of the electrode of the plug 16 and the upper side of 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 having 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. Therefore, at least the output signals from the crank angle sensor 9, the air flow sensor 31, the linear O2 sensor 38, and the like that detect the rotation angle (engine speed) of the crankshaft 7 are input to the ECU 50, and in addition, the accelerator 50 An output signal from an accelerator opening sensor 51 for detecting 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 at 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 maximum. Fuel within the crank angle range of approximately the maximum lift at which the intake valve 12 lifts more than 3/4 of the maximum lift amount, for example, within the crank angle range of 60 ° to 150 ° after the intake top dead center, centering on the lifted crank angle Is uniformly 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. Further, as shown in FIG. 5B, the map at the time of cold is uniformly set to 20 MPa in the entire operation region where uniform combustion is performed. 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.

  Here, each nozzle diameter is set as follows. The nozzle diameters of the first nozzle hole and the fourth to eighth nozzle holes are the same diameter, for example, set to 0.15 mm, and the nozzle diameters of the second and third nozzle holes are the same diameter. , Smaller than the first, fourth to eighth nozzles, for example, 0.14 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.

  Moreover, since the nozzle diameters of the second and third nozzle holes arranged within the movable range of the intake valve 12 are set smaller than the other nozzle diameters, the flow rate of fuel injected from the nozzle holes is reduced. Therefore, even if the fuel spray collides with the intake valve 12, the impact degree of the collision can be suppressed.

  In addition, since the first nozzle hole and the second and third nozzle holes are set to have different nozzle diameters among the first to third nozzle holes arranged in the vicinity of the electrode E of the spark plug, the first nozzle hole, Since the fuel spray penetration force differs between the second and third nozzles, as shown in FIG. 10, the time when the combustible air-fuel mixture is formed around the electrode E of the spark plug by the fuel spray injected from the first nozzle The fuel spray injected from the second and third nozzles causes a difference in the timing when the combustible air-fuel mixture is formed around the electrode E of the spark plug, and the combustible air-fuel mixture remains in the vicinity of the electrode E of the spark plug for a long time. And ignitability during stratified combustion can be improved.

  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 arranged in the vicinity of the electrode E of the spark plug, there are the following requirements.

  That is, during the warm period when stratified combustion is performed, the atomized air-fuel mixture is collected in the vicinity of the electrode E of the spark plug, so that it is necessary to produce a mutual interference effect in each fuel spray near the electrode E of the spark plug. At the time of cold start, if this mutual interference effect occurs, conversely, 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 combustion is performed at a warm time, for example, when the fuel pressure is 12 MPa and the in-cylinder pressure is 1 MPa, as shown in FIG. 11A, the spray angle α1 of the fuel injected from the first injection port, The spray angle α2 (<α1) of the fuel injected from the second nozzle hole (third nozzle hole) 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, α2 are close to each other, and a mutual interference effect is produced 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 angles α1 and α2 are 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 vaporizes and the vaporized fuel spreads outward. is there. 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. 11B, the fuel injected from the first injection port Both the spray angle α1 ′ and the spray angle α2 ′ (<α1 ′) of the fuel injected from the second nozzle (third nozzle) become smaller, and the opening angle θ1 between the first nozzle and the second nozzle (third nozzle). The angle is smaller than. Accordingly, the spray angles α1 ′ and α2 ′ are positioned away from each other, and the above-described mutual interference effect is not generated.

  Note that the spray angles α1 ′ and α2 ′ during cold start are small because both the fuel pressure and the in-cylinder pressure are low, and the friction between the fuel and the in-cylinder air is small. This is because the spread is small.

  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 10 MPa and the in-cylinder pressure is 1 MPa, as shown in FIG. 12 (a), the spray of fuel injected from the first nozzle hole and the fifth nozzle hole 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 a mutual interference effect is not generated between these fuel sprays.

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. 12 (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.
Therefore, the spray angles α4 are positioned away from each other, and the above-described mutual interference effect is not generated.

  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, and the mutual interference effect as described above acts more, so that the spray penetration force L becomes excessively large, and the injected fuel spray is reduced. There arises a problem that it passes through the vicinity of the electrode E of the spark plug 16 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, the fuel sprays are separated too much, and the above-described mutual interference effect cannot be obtained.

  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. 14 (a), at a position 20 mm downstream from the nozzle point A of the fuel injection valve 18, two points B and C where the imaginary plane through which the spray center line passes and the contour of the fuel spray intersect are determined. The spray angle α is defined by ∠BAC (α = ∠BAC).
Further, as shown in FIG. 14B, the distance from the most advanced portion of the spray with respect to the axial direction of the fuel injection valve 18 is defined as the spray penetration force L.

  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 since the sample particle area is brightened by the laser sheet light, the spray is sprayed from the portion where the brightness changes in the photographed image. 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 of the fuel injection valve 18 and the axis L2 of the second injection port. 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 the 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 the 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.

  Moreover, since the nozzle diameters of the second and third nozzle holes arranged within the movable range of the intake valve 12 are set smaller than the other nozzle diameters, the flow rate of fuel injected from the nozzle holes is reduced. Therefore, even if the fuel spray collides with the intake valve 12, the impact degree of the collision can be suppressed.

  In addition, since the first nozzle hole and the second and third nozzle holes are set to have different nozzle diameters among the first to third nozzle holes arranged in the vicinity of the electrode E of the spark plug, the first nozzle hole, Since the fuel spray penetration force differs between the second and third nozzles, the time when the combustible air-fuel mixture is formed around the electrode E of the spark plug by the fuel spray injected from the first nozzle, and the second and third nozzles A difference occurs with the time when the combustible air-fuel mixture is formed around the electrode E of the spark plug due to the fuel spray injected from, and the combustible air-fuel mixture can exist in the vicinity of the electrode E of the spark plug for a long time. Can improve the ignitability.

  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, the mutual interference effect between the fuel sprays can be reliably obtained, and the ignitability can be improved. At the same time, the electrode E of the spark plug 16 can be arranged in the peripheral spray region b where the atomized fuel is distributed, and it is possible to suppress the non- atomized fuel 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 increased 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 flow rate is fast, so that mixing of the fuel and air is performed effectively, and the mixture can be made more uniform.

In the present embodiment, an example in which the nozzle diameter is changed in changing the fuel spray penetration force has been described. However, both the nozzle length or the nozzle diameter and the nozzle path length may be changed. .
For example, when the spray penetration force is increased, the nozzle diameter d1 and the nozzle passage length l1 shown in FIG. 15A are increased to the nozzle diameter d2 as shown in FIG. If the length is increased to 12, the spray penetration force can be increased. On the contrary, when the spray penetration force is reduced, the nozzle diameter d1 may be reduced and the nozzle passage length l1 may be shortened.

  Further, in the present embodiment, as the nozzle holes arranged in the vicinity of the electrode E of the spark plug 16, a first nozzle hole whose axial center is directed to the lower side of the electrode E, and first and second whose axial centers are directed to both sides of the electrode side. Although the example in which the second nozzle hole is positioned and the electrode E is surrounded by the first to third nozzle holes is shown, as shown in FIG. 16, the first nozzle hole is positioned adjacent to both sides of the first nozzle hole. The nozzle hole to the third nozzle hole may be arranged in parallel. In this case, the first nozzle hole corresponds to the first electrode lower nozzle hole, and the second and third nozzle nozzles correspond to the second electrode lower nozzle nozzle in the claims.

  Further, in the present embodiment, an example of the multi-hole type fuel injection valve 18 having eight injection holes is shown, but 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. The AA arrow directional view of FIG. The perspective view which shows the fuel-injection state from the fuel injection valve which concerns on embodiment of this invention. The figure which shows the fuel-air mixture distribution state around the electrode of the spark plug with respect to the crank angle change 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 warm 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 fuel at the time of cold start The figure which shows the relationship between the spray angle 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 spray angle of the fuel at the time of cold start The figure which shows the relationship between 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. Explanatory drawing explaining the spray penetration force change method which concerns on other embodiment of this invention. Explanatory drawing which shows arrangement | positioning of the nozzle hole which concerns on other embodiment of this invention.

Explanation of symbols

1: Engine 6: Combustion chamber 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)
L: Maximum lift position of intake valve (movable range of intake valve)
O: Axis center O1: Axis of first nozzle hole (axis center of electrode lower nozzle hole, axis of first electrode nozzle hole)
O2: axis of the second nozzle hole (axis of the electrode side nozzle hole, axis of the second electrode lower nozzle hole)
O3: Axis of third nozzle hole (axial center of electrode side nozzle hole, axial center of second electrode lower nozzle hole)
α1, α2, α1 ′, α2 ′, α3, α4: Spray angle θ1, θ2: Opening angle L: Spray penetration force

Claims (2)

A fuel injection unit that includes an ignition plug disposed in the combustion chamber and a fuel injection valve disposed between the two intake valves so that a tip portion thereof faces the periphery of the combustion chamber, and is injected from the fuel injection valve In a spark ignition direct injection engine whose direction is directed near the electrode of the spark plug,
The fuel injection valve is provided with a plurality of injection holes so as to be positioned in the vicinity of the electrode of the ignition plug , and at least the axis of the ignition plug is seen from the fuel injection valve side when viewed from the front end side in the fuel injection direction. An electrode lower side nozzle hole directed to a space near the lower surface of the electrode, and an electrode side nozzle hole whose axial center is directed to a space near the electrode side of the ignition plug,
The both nozzle holes are located at the tip end side in the injection direction centering on the axis of the fuel injection valve, the electrode lower nozzle holes are positioned outside the movable range of the two intake valves, and the electrode side nozzle holes are Set to be within the movable range of both intake valves, and
A spark ignition type direct injection engine characterized in that a spray penetration force of the fuel injected from the electrode side injection port is set smaller than a spray penetration force of the fuel injected from the electrode lower injection port . The axial center of the electrode side nozzle hole is set to be positioned above the umbrella portion of the intake valve in the middle of the intake stroke when the lift amount of the intake valve is large, and
Fuel injection timing control means for setting the fuel injection timing injected from the fuel injection valve according to the operating state of the engine,
2. The spark ignition direct injection engine according to claim 1, wherein the fuel injection timing control means sets the fuel injection timing at the time of uniform combustion to the middle stage of the intake stroke where the lift amount of the intake valve is large .

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