JP4186771B2 - 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.

  Further, as a result of earnest research, the present inventors have devised the relationship between the spray angles injected from the respective nozzle holes when the multi-hole type injector is used as described above, and thereby the fuel sprays injected from the respective nozzle holes It was found that a mutual interference effect can be obtained.

  The mutual interference effect will be described in detail. First, it has been found that the mutual interference effect occurs when the fuel sprays approach each other by setting the opening angle and the spray angle between the axial centers of the nozzle holes.

  In other words, when the fuel sprays injected from the nozzles approach each other, the air volume in the space between the fuel sprays decreases, the degree of the air around the fuel sprays caught in the fuel sprays decreases, and the fuel spray speed increases. Become.

  As a result, the pressure in the space between the fuel sprays is reduced, the fuel sprays are attracted to each other, and the fuel spray rate is increased, so that the air-fuel mixture on the center side between the fuel sprays is atomized and concentrated. Thus, the air-fuel mixture on the peripheral side becomes a finely atomized thin air-fuel mixture.

  Therefore, the atomized rich air-fuel mixture can be collected in the vicinity of the electrode, and the ignitability can be improved.

  As described above, not only using a multi-hole type injector, but also improving the ignitability by setting the relationship between the opening angle and the spray angle between the axis of each nozzle so that a mutual interference effect occurs. Is something that can be done.

  However, when a multi-hole type injector is used as described above and the relationship between the spray angles injected from the respective nozzle holes is set so that a mutual interference effect occurs, the ignitability is warm in the stratified combustion. Although improved, there is a problem that ignitability is deteriorated because a rich air-fuel mixture collects in the vicinity of the electrode of the spark plug at the time of cold, particularly at the time of cold start.

  In other words, even though the mixture is atomized, the ignitability is poor at the time of cold start, and the fuel injection amount is increased. Therefore, a large amount of atomized mixture adheres to the electrode and the ignitability deteriorates. Because.

  The present invention has been made in view of the above-described problems, and its purpose is to improve the ignitability due to the mutual interference effect between the fuel sprays during the warm time while maintaining the ignitability during the cold start. It is to provide a spark ignition type direct injection engine that is possible.

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 combustion chamber are injected from the fuel injection valve. In a spark ignition direct injection engine in which the fuel injection direction is directed near the electrode of the spark plug,
The injection timing of the fuel injected from the fuel injection valve is set to a compression stroke when the engine temperature is a predetermined value or more, and when the engine temperature is lower than the set value, the intake stroke is set. Fuel injection timing control means to be set to
A fuel pressure adjusting means for adjusting the pressure of the fuel supplied to the fuel injection valve to a higher fuel pressure at the time of warming than at the time of starting in the cold time;
The fuel injection valve has at least an electrode lower injection port whose axis is directed to a space close to the lower surface of the electrode of the spark plug when viewed from at least the fuel injection direction tip side from the fuel injection valve side, and the axis is the above An electrode side nozzle hole directed to a space close to the side of the electrode of the spark plug,
Spray angle of fuel or we injected the both injection port, the time between the temperature becomes larger than the opening angle between the axis of both jetting nozzle, the time of starting at between the cold axis of both spray port It is configured to be less than the opening angle.

  Here, the mutual interference effect is affected by the fuel spray angle, and this spray angle is affected by the fuel pressure and the in-cylinder pressure.

  That is, the spray angle of the fuel is widened because the fuel is vaporized by friction between the fuel and the air in the cylinder when the fuel is injected into the cylinder, and the vaporized fuel spreads outward.

  The spread of the spray angle becomes larger as the fuel pressure and the in-cylinder pressure are higher because the friction is larger.

  Specifically, at the warm time when stratified combustion is performed, a high fuel pressure for stratified combustion is set, and the fuel injection timing is set in the compression process, so that the in-cylinder pressure at the time of fuel injection is also high. Therefore, at the warm time, since both the fuel pressure and the in-cylinder pressure are large, the spray angle is also large.

  On the other hand, at the cold start in which non-stratified combustion (homogeneous combustion) is performed, the increase in fuel pressure is delayed due to the delay in driving the engine-driven high-pressure fuel pump, the fuel pressure becomes low, and the fuel injection Since the timing is set to the intake stroke, the in-cylinder pressure at the time of fuel injection is also low. Therefore, at the time of cold start, both the fuel pressure and the in-cylinder pressure are small, and the spray angle is small.

  According to the first configuration of the present invention, at the time of warm, both the fuel pressure and the in-cylinder pressure are high and the spray angle is easy to spread, and the opening angle between the shaft centers of both the fuel injection valves is from the both nozzles. Since it is less than the spray angle of the injected fuel, the air volume in the space between the spray angles injected from both nozzles is reduced, and the mutual interference effect of each fuel spray described above is obtained, improving ignitability can do.

  Further, when cold, both the fuel pressure and the in-cylinder pressure are low and the spray angle is difficult to spread, and the opening angle is made larger than the spray angle. Since the air volume in the space is increased and the above-described mutual interference effect can be suppressed, it is possible to suppress the deterioration of ignitability due to a large amount of atomized air-fuel mixture adhering to the electrode.

In the second configuration of the present invention, in the spark ignition direct injection engine having the same premise as the first configuration, the fuel for setting the injection timing of the fuel injected from the fuel injection valve to either the compression stroke or the intake stroke Injection timing control means;
A fuel pressure adjusting means for adjusting the pressure of the fuel supplied to the fuel injection valve to a higher fuel pressure than when the fuel injection timing is set in the intake stroke when the fuel injection timing is set in the compression stroke;
The fuel injection valve has at least an electrode lower injection port whose axial center is directed to a space near the lower surface of the electrode of the spark plug when viewed from at least the fuel injection direction tip side from the fuel injection valve side, and the shaft center is the above-mentioned An electrode side nozzle hole directed to a space close to the side of the electrode of the spark plug,
When the fuel injection timing is set to the compression stroke, the spray angle of the fuel injected from both the nozzles becomes larger than the opening angle between the shaft centers of the both nozzles, and when the fuel injection timing is set to the intake stroke It is comprised so that it may become below the opening angle between the axial centers of both the above-mentioned nozzle holes .

According to the second configuration of the present invention, when the fuel injection timing is set to a compression stroke with a high in-cylinder pressure, the fuel pressure is adjusted to a high fuel pressure for stratified combustion, and is the same as in the warm mode in the first configuration. Since both the fuel pressure and the in-cylinder pressure increase, the spray angle increases and the air volume in the space between sprays decreases. Therefore, the mutual interference effect of each fuel spray mentioned above is acquired, and ignitability can be improved.

On the other hand, when the fuel injection timing is set to the intake stroke where the in-cylinder pressure is low, the fuel pressure is adjusted to be lower than that during the stratified combustion, and both the fuel pressure and the in-cylinder pressure are the same as during the cold start in the first configuration. Since it becomes low, a spray angle becomes small, the air volume in the space between sprays increases, and the mutual interference effect mentioned above can be suppressed. Therefore, it can suppress that atomized air-fuel | gaseous mixture adheres to an electrode in large quantities and ignitability deteriorates.

  In the third configuration of the present invention, the opening angle between the axial centers of the two nozzle holes is set between 15 and 25 degrees.

  As a result of diligent research by the present inventors, when the opening angle between the axial centers of each nozzle hole is in the range of 15 to 25 °, the mutual interference effect between the fuel sprays is appropriately suppressed while being suppressed. It was confirmed that a good mutual interference effect was obtained.

  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 third configuration of the present invention, since the opening angle between the axial centers of the two nozzle holes is set between 15 and 25 °, the mutual interference effect between the fuel sprays is suppressed from becoming excessively large. However, since an appropriate mutual interference effect is obtained, the ignitability can be improved.

  In the fourth configuration of the present invention, the distance from both the nozzle holes to the electrode of the spark plug is set to 20 mm or more.

  Here, according to the earnest studies by the present inventors, the above-described mutual interference effect is that the fuel spray injected from each nozzle gradually spreads in a conical shape according to the distance away from each nozzle, It has been found through analysis and experiment that the above-mentioned mutual interference effect occurs when the distance of the fuel spray is close to 20 mm from the nozzle.

  According to the 4th structure of this invention, since the distance from both nozzles to the electrode of a spark plug is set to 20 mm or more, a mutual interference effect can be acquired reliably and ignitability can be improved.

  ADVANTAGE OF THE INVENTION According to this invention, the ignitability by the mutual interference effect between the fuel sprays at the time of warm can be improved, maintaining the ignitability at the time of cold start.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Embodiment 1)
FIG. 1 is an overall configuration diagram of a spark ignition direct injection engine 1 according to Embodiment 1 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. The region other than the stratified combustion region is a uniform combustion region. The fuel is injected by the fuel injection valve 18 in the intake stroke of the cylinder 2 and sufficiently mixed with the intake air. Uniform combustion is performed in which the gas is burned after forming the. 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 as a point of the present invention will be described with reference to FIGS. 2, 6, and 7.

  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; FIG. 7 is a perspective view showing a state in which fuel is injected from each injection port of the multi-hole type fuel injection valve 18.

  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 valves.

  Further, the axial center L2 of the second 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 (left side in the figure).

  Further, 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 drawing).

  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, the axis L4 of the fourth nozzle hole is arranged so as to be directed from the axis 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.

  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. 7, 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, 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 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 between the fuel sprays, while at the cold start, When this mutual interference effect 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 axis L1 of the first nozzle hole and the axis L2 of the second nozzle hole, and the axis L1 of the first nozzle hole and the axis L3 of the third nozzle hole, which are centered around the electrode E of the spark plug, The spray angle α of the fuel injected from each nozzle hole and the opening angle θ of each nozzle hole are 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 warm stratified combustion is performed, for example, when the fuel pressure is 12 MPa and the in-cylinder pressure is 1 MPa, as shown in FIG. 8A, 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.

  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 where 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 is too long, a mutual interference effect occurs between the fuel sprays between the first nozzle hole and the fifth nozzle hole, and the fuel spray injected from the first nozzle hole is drawn toward the fifth nozzle hole and mixed in the vicinity of the electrode E of the spark plug. You may not be able to collect your mind.

  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. 9A, 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 do not cause the above-described 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. 9B, injection is performed from the first and fifth nozzles. 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, 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, the fuel sprays are too far apart, causing a problem that the mutual interference effect between the fuel sprays 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. 11 (a), at a position 20 mm downstream from the nozzle part A of the fuel injection valve 18, two points B and C at which 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. 11 (b), 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 first 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 obtained. 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.

  Further, since the fourth to eighth nozzle holes are arranged outside the movable range of the intake valve 12, the collision of the fuel spray injected from the nozzle hole to the intake valve 12 is suppressed as much as possible around the electrode E of the spark plug 16. The air-fuel mixture can be collected, and the ignitability can be improved.

  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 in which the dispersed fuel is distributed, and it is possible to suppress the mixture that has not been atomized 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, at the time of uniform combustion, fuel is injected from the fourth to eighth nozzles arranged on the piston side, so that the air-fuel mixture can be dispersed throughout the combustion chamber, and the air-fuel mixture in the combustion chamber 6 is made uniform. Can be achieved.

  In the first embodiment, the present invention is applied to the multi-hole type fuel injection valve 18 having eight injection holes. However, the present invention is applied to a multi-hole type fuel injection valve having other number of injection holes. You may do it.

(Embodiment 2)
Next, Embodiment 2 will be described with reference to FIGS.
12 is a longitudinal sectional view of the cylinder head according to the second embodiment, FIG. 13 is a plan view of the cylinder head according to the second embodiment, and FIG. 14A is a spray angle during warming, the first nozzle hole, the second nozzle nozzle, and the third nozzle nozzle. FIG. 14B is a diagram showing the relationship between the spray angle during cold and the opening angle between the first nozzle hole and the second and third nozzle holes.

  In the first embodiment, an example of a side injection type spark ignition type direct injection engine in which the tip of the fuel injection valve 18 is arranged at the periphery of the combustion chamber 6 is shown in the present embodiment. An example in which the tip is applied to a center-injection type spark-ignition direct-injection engine in which the tip is disposed in the vicinity of the approximate center of the combustion chamber 6 is shown.

  12 and 13, the spark plug 16 is disposed at a predetermined inclination angle with respect to the axial center m of the cylinder in the vicinity of the approximate center of the combustion chamber 6.

  Further, the fuel injection valve 18 is disposed substantially parallel to the cylinder axis m near the center of the combustion chamber 6.

  The fuel injection valve 18 shows an example of a multi-hole type fuel injection valve having three injection holes.

  The three injection holes of the fuel injection valve 18 are the first injection hole in which the injected fuel spray A1 is directed below the electrode E of the spark plug 16, and the injected fuel sprays A2 and A3 are the electrodes of the spark plug 16. It is comprised from the 2nd, 3rd nozzle hole each directed to both sides.

  The first nozzle hole corresponds to the electrode lower nozzle hole, and the second and third nozzle nozzles correspond to the electrode side nozzle nozzle in the claims.

  And these nozzle holes are set so that the spray angle α of the fuel injected from each nozzle hole and the opening angle θ of each nozzle hole have the relationship shown below, as in the first embodiment (FIG. 8). .

  As shown in FIG. 14 (a), first, when warm stratified combustion is performed, for example, when the fuel pressure is 10 MPa and the in-cylinder pressure is 1 MPa, injection is performed from the first injection port and the second injection port (third injection port). The fuel spray angle α5 is widened and is larger than the opening angle θ3 between the first nozzle hole and the second nozzle hole (third nozzle hole).

  Accordingly, the spray angles α5 approach each other, and a mutual interference effect is generated between the fuel sprays.

  Further, at the time of cold 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, the spray angle of the fuel injected from the first injection port and the second injection port (third injection port) Both α5 are small, and the angle is smaller than the opening angle θ3 between the first nozzle hole and the second nozzle hole (third nozzle hole).

  Accordingly, the spray angles α5 are located away from each other, and the above-described mutual interference effect is not generated.

  As described above, according to the second embodiment, as in the first embodiment, at the warm time, both the fuel pressure and the in-cylinder pressure are high, and the axis of the first nozzle hole of the fuel injection valve 18 is easy to spread. The opening angle θ between L1 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, respectively, are sprays of fuel injected from both the nozzle holes. Since the angle α is equal to or less than the angle α, the air volume in the space between the spray angles α injected from both nozzles is reduced, and the mutual interference effect of each fuel spray described above can be obtained, so that the ignitability can be improved. .

  In the cold state, 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 spray angle α injected from both nozzles Since the air volume in the space between the two increases and the above-described mutual interference effect can be suppressed, it is possible to suppress a large amount of atomized air-fuel mixture from adhering to the electrode E and deteriorating the ignitability.

  In the second embodiment, the fuel injection valve 18 is arranged at the center of the combustion chamber 6. However, as shown by a two-dot chain line in FIG. 13, the fuel injection valve 18 is arranged in the vertical direction on the peripheral side of the combustion chamber 6. Also good.

  In the second embodiment, an example of the multi-hole type fuel injection valve 18 having three injection holes is shown. However, four or more injection holes are provided to allow the mixture to be dispersed in the combustion chamber 6. A multi-hole fuel injection valve may be applied.

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 1 of this invention. 1 is a schematic diagram of a fuel supply system according to Embodiment 1 of the present invention. (A) is a figure which shows the fuel-injection control map at the time of warm which concerns on Embodiment 1 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 1 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 around the axial center of the fuel injection valve which concerns on Embodiment 1 of this invention. The perspective view which shows the fuel-injection state from the fuel injection valve which concerns on Embodiment 1 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 1 of this invention, and the opening angle of a 1st nozzle hole, and a 2nd, 3rd nozzle hole, (b) is at the time of cold start The figure which shows the relationship between the spray angle of the 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 1 of this invention, and the opening angle of a 1st nozzle hole, and a 5th nozzle hole, (b) is the fuel of the time of a cold start The figure which shows the relationship between the spray angle and the opening angle of the 1st nozzle hole and the 5th nozzle hole. Explanatory drawing which shows the spray state of the fuel spray which concerns on Embodiment 1 of this invention. Explanatory drawing explaining the definition of the spray angle which concerns on Embodiment 1 of this invention, and the spray penetration force. The longitudinal cross-sectional view of the cylinder head which concerns on Embodiment 2 of this invention. The top view of the cylinder head which concerns on Embodiment 2 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 1 of this invention, and the opening angle of a 1st nozzle hole, and a 2nd, 3rd nozzle hole, (b) is at the time of cold start The figure which shows the relationship between the spray angle of the fuel, and the opening angle of a 1st nozzle hole, and a 2nd, 3rd nozzle hole.

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)
V: Maximum lift position of intake valve (movable range of intake valve)
L: axial center of the fuel injection valve L1: axial center of the first nozzle hole (axial center of the 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)
A1: Spray angle of fuel injected from the first nozzle port A2: Spray angle of fuel injected from the second nozzle port A3: Spray angle of fuel injected from the third nozzle port α1, α2, α3, α4, α5: Spray Angle θ1, θ2, θ3: Opening angle

Claims (4)

A spark plug disposed in the combustion chamber; and a fuel injection valve disposed such that a tip thereof faces the combustion chamber; a fuel injection direction injected from the fuel injection valve is in the vicinity of an electrode of the spark plug In the spark ignition direct injection engine oriented to
The injection timing of the fuel injected from the fuel injection valve is set to the compression stroke when the engine temperature is higher than a predetermined value, and when the engine temperature is lower than the set value, the intake stroke is set. Fuel injection timing control means to be set to
A fuel pressure adjusting means for adjusting the pressure of the fuel supplied to the fuel injection valve to a higher fuel pressure at the time of warming than at the time of starting in the cold time;
The fuel injection valve has at least an electrode lower injection port whose axial center is directed to a space near the lower surface of the electrode of the spark plug when viewed from at least the fuel injection direction tip side from the fuel injection valve side, and the shaft center is the above-mentioned An electrode side nozzle hole directed to a space close to the side of the electrode of the spark plug,
Spray angle of fuel or we injected the both injection port, the time between the temperature becomes larger than the opening angle between the axis of both jetting nozzle, the time of starting at between the cold axis of both spray port A spark-ignition direct injection engine characterized by being set to be less than the opening angle. A spark plug disposed in the combustion chamber; and a fuel injection valve disposed such that a tip thereof faces the combustion chamber; a fuel injection direction injected from the fuel injection valve is in the vicinity of an electrode of the spark plug In the spark ignition direct injection engine oriented to
Fuel injection timing control means for setting the injection timing of the fuel injected from the fuel injection valve to either the compression stroke or the intake stroke;
A fuel pressure adjusting means for adjusting the pressure of the fuel supplied to the fuel injection valve to a higher fuel pressure than when the fuel injection timing is set in the intake stroke when the fuel injection timing is set in the compression stroke;
The fuel injection valve has at least an electrode lower injection port whose axis is directed to a space close to the lower surface of the electrode of the spark plug when viewed from at least the fuel injection direction tip side from the fuel injection valve side, and the axis is the above An electrode side nozzle hole directed to a space close to the side of the electrode of the spark plug,
When the fuel injection timing is set to the compression stroke, the spray angle of the fuel injected from both the nozzles becomes larger than the opening angle between the shaft centers of the both nozzles, and when the fuel injection timing is set to the intake stroke features and to that sparks ignition direct injection engine that are set to be less than the open angle between the axis of both jetting nozzle.   The spark-ignition direct injection engine according to claim 1 or 2, wherein an opening angle between the axial centers of the two nozzle holes is set between 15 and 25 degrees.   The spark ignition type direct injection engine according to any one of claims 1 to 3, wherein a distance from both the nozzle holes to the electrode of the spark plug is set to 20 mm or more.

Images