JP4622852B2 - Spark ignition direct injection engine - Google Patents

Description

The present invention relates to a spark ignition direct injection engine having a fuel injection valve having a plurality of injection holes.

Conventionally, as disclosed in Patent Document 1, a spark plug is provided, and a fuel injection valve (injector) that directly supplies fuel into the combustion chamber is provided, and a spark is made to improve fuel consumption by performing stratified combustion. Ignition type direct injection engines are known. When stratified combustion is performed, when two intake valves are provided in one cylinder, a fuel injection valve is also disposed at the peripheral edge of the combustion chamber between the two intake valves in a plan view. When the nozzle hole of the fuel injection valve is directed directly to the electrode, there is a problem that the fuel tends to adhere to the electrode as droplets and the ignitability deteriorates. For this reason, in Patent Document 1, the fuel injection valve disposed in the peripheral portion of the combustion chamber is, for example, a multi-hole type having eight injection holes, and three of the injection holes are directed downward near the electrodes of the spark plug. As a lower nozzle (specific nozzle), a left nozzle directed to the left in the vicinity of the electrode, and a right nozzle directed to the right in the vicinity of the electrode, a rich mixture layer is formed in the vicinity of the electrode by fuel spray from these three nozzles. What has been made to obtain the stratification to form is disclosed.

Patent Document 1 discloses one in which five nozzle holes other than the above three nozzle holes are directed to a piston top surface that is a part away from an electrode for uniform combustion. And in the thing of patent document 1, the nozzle hole which has an axial line (axial center) nearest to the axial center of a fuel injection valve is set so that a piston side may turn into a nozzle hole located in the downward direction of a lower nozzle hole among nozzle holes. Have been disclosed.

Patent Document 1 further discloses the following technical contents. That is, in a predetermined operating region where the engine is running at a low speed and a low load, fuel injection is performed during the compression stroke to generate a rich air-fuel mixture around the electrode for stratified combustion, while in other operating regions It is disclosed that fuel is injected during the stroke to perform uniform combustion. It has also been proposed to effectively enrich the periphery of the spark plug electrode by utilizing the mutual interference effect between the fuel sprays injected from a plurality of nozzles. Patent Document 2 also discloses a multi-hole fuel injection valve similar to Patent Document 1 provided at the periphery of the combustion chamber.

Further, Patent Document 3 discloses a multi-hole type fuel injection valve provided in a substantially central portion of a combustion chamber like an ignition plug. In this patent document 3, the fuel spray from the fuel injection valve is directed to the piston top surface so that the fuel spray reflected and raised by the piston top surface passes through the vicinity of the electrode. . Further, Patent Document 4 discloses a device that changes the valve opening characteristics of the intake valve, particularly a device that can change the opening / closing timing, the lift amount, etc. by combining the phase change mechanism and the lift amount change mechanism. ing.
JP 2005-98119 A JP 2005-273554 A Japanese Patent Laying-Open No. 2005-256791 JP 2004-301058 A

As described above, when the fuel injection valve disposed between the two intake valves in the plan view in the periphery of the combustion chamber has the left injection port and the right injection port directed to the left and right sides near the electrode. When fuel is injected during the intake stroke in the cold low load range, a large amount of fuel spray from the left and right nozzles adheres to the cylinder inner wall (cylinder liner) located on the opposite side of the fuel injection valve As a result, problems such as dilution of engine oil occur. In other words, when the engine is started when it is cold and the engine is not sufficiently warmed up, the fuel spray injected from the left and right injection ports is in the middle of the low load range, so the in-cylinder flow is weak. Because it is not vaporized and atomized sufficiently, it adheres to the cylinder inner wall on the opposite side of the fuel injection valve, and the cylinder inner wall itself is also cooled, so most of the adhered fuel spray is vaporized and atomized. It will remain attached without being attached. Of course, if the fuel spray remains on the inner wall surface of the cylinder, not only dilution of the engine oil but also generation of unburned components becomes undesirable.

The present invention has been made in view of the above circumstances, and its purpose is spark ignition that can prevent or suppress the situation where a large amount of fuel spray remains attached to the inner wall surface of the cylinder. It is to provide a direct injection engine.

In order to achieve the above object, the following solution is adopted in the spark ignition direct injection engine of the present invention. That is, as described in claim 1 in the claims,
For each cylinder, two intake valves, a spark plug disposed so that an electrode is positioned at substantially the center of the combustion chamber, and a combustion chamber peripheral portion between the two intake valves in a plan view. And a multi-hole fuel injection valve having a plurality of injection holes for directly injecting fuel into the combustion chamber,
As the plurality of nozzle holes, at least a left nozzle hole directed near the left side of the electrode, a right nozzle hole directed near the right side of the electrode, and a lower nozzle hole directed near an extension line near the tip of the electrode In a spark ignition direct injection engine set to have
The spray angle from the right nozzle and the spray angle from the left nozzle are respectively set to be within the movable range of the intake valve, while the spray angle from the lower nozzle is outside the movable range of the intake valve. Is set to be
Set so that fuel injection is performed at the timing when fuel spray from the left and right nozzles collides with the intake valve in the predetermined operating range, which is a low load range before engine warm-up. Being
It is like that. According to the above solution, the fuel spray from the left and right nozzles collides with the intake valve on the way, so that a large amount of fuel spray adheres to the inner wall surface of the cylinder opposite to the fuel injection valve. It will be prevented or suppressed. Moreover, vaporization and atomization of the fuel spray are promoted by the collision of the fuel spray with the intake valve.

A preferred mode based on the above solution is as described in claim 2 and the following claims. That is,
In the predetermined operating range, the intake valve is opened slowly at a position that is greatly delayed from the intake top dead center in the intake stroke (corresponding to claim 2). In this case, since the intake air is introduced into the cylinder at a time when the piston speed is sufficiently increased due to the slow opening of the intake air, the intake air flow in the cylinder is increased, fuel vaporization and atomization are promoted, The amount of fuel spray adhering to the cylinder inner wall surface opposite to the fuel injection valve is also reduced. Of course, the pumping gloss is reduced by the slow opening of the intake air.

  In the predetermined operation region after the temperature increase control for positively raising the exhaust gas temperature by retarding the ignition timing greatly after starting the engine, the fuel spray from the left and right nozzles collides with the intake valves. The fuel injection is executed (corresponding to claim 3). In this case, the exhaust gas temperature rise and thus the temperature of the engine, i.e., the intake valve, is promptly raised by a large retarded ignition timing, which is more preferable in terms of vaporizing and promoting atomization of the fuel spray colliding with the intake valve. Become.

In the predetermined operation region, the closing timing of the intake valve that has been slowly opened is set to be substantially the intake bottom dead center position (corresponding to claim 4). In this case, the opening period of the intake valve can be ensured as much as possible, that is, the intake charge / amount can be sufficiently ensured.

  In the predetermined operating region, the valve opening timing of the intake valve gradually approaches the intake top dead center as the engine temperature rises, and the valve opening period is extended (corresponding to claim 5). In this case, since the valve opening period is changed to a state in which the valve opening period is sufficiently ensured as the engine temperature rises, it is preferable for ensuring the intake charge / amount and promoting warm-up.

  In the predetermined operation region, fuel injection is performed such that fuel sprays from the left and right injection ports collide with the intake valve at least at the maximum lift position (corresponding to claim 6). In this case, fuel injection is performed at the timing when the intake air flow in the cylinder becomes large, which is preferable in terms of vaporization of fuel spray and promotion of atomization.

The distance from each of the lower nozzle hole, the left nozzle hole and the right nozzle hole to the electrode is set to 20 mm or more,
The opening angle formed between the lower nozzle hole and the left nozzle hole is set in a range of 15 degrees to 25 degrees, and fuel spray from the lower nozzle hole is generated in a predetermined operation region that is a low rotation / low load region of the engine. The fuel spray from the left nozzle is set to be continuous with each other by the mutual interference effect,
An opening angle between the lower nozzle and the right nozzle is set in a range of 15 to 25 degrees, and the fuel spray from the lower nozzle and the fuel spray from the right nozzle are mutually in the predetermined operation region. Set to be continuous with each other due to interference effects,
(Corresponding to claim 7). In this case, the stratified state around the electrode is such that when the electrode is viewed from the fuel injection valve, the rich air-fuel mixture becomes substantially V-shaped and surrounds the lower and left and right sides of the electrode. As a result, a very preferable state can be obtained.

According to the present invention, it is possible to prevent or suppress a situation in which a large amount of fuel spray remains attached to the cylinder inner wall surface.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, an overview of the whole will be described, and then details of fuel injection control will be described.

FIG. 1 shows a spark ignition direct injection engine 1. This engine 1 is an in-line multi-cylinder (four cylinders in the embodiment) engine having a plurality of cylinders 2 in series in a direction perpendicular to the plane of the drawing (in FIG. 1). Only one cylinder is shown). Each cylinder 2 has a cylinder block 3 and a cylinder head 4 disposed on the cylinder block 3, and a piston 5 is fitted into the cylinder 2 so as to be reciprocally movable in the vertical direction. A combustion chamber 6 is defined in the cylinder 2 between the piston 5 and the cylinder head 4. The combustion chamber 6 is a so-called pent roof type combustion chamber having two inclined surfaces extending from a substantially central portion in the ceiling portion of the cylinder 2 to the vicinity of the lower end surface of the cylinder head 4.

As shown in FIG. 2, the cylinder head 4 is formed with two intake ports 10 (when the two intake ports are distinguished, they are indicated by reference numerals 10A and 10B) and two exhaust ports 11 are formed. (Only one is disclosed in FIG. 1). One end of each of the two intake ports 10 is opened to the combustion chamber 6 from one of the inclined surfaces of the ceiling portion of each cylinder 2, and the other end of the two intake ports 10 extends obliquely upward from the combustion chamber 6. Opened independently from each other (on the right side in FIG. 1). At the opening end of each intake port 10 on the combustion chamber 6 side, an intake valve 12 that is opened and closed at a predetermined timing is disposed (only one is disclosed in FIG. 1). One end of each of the two exhaust ports 11 is opened to the combustion chamber 6 from the other of the inclined surfaces in the ceiling portion of each cylinder 2, and the other end side of the two exhaust ports 11 extends substantially horizontally after joining one in the middle. The other end surface (left side surface in FIG. 1) of the engine 1 is opened. An exhaust valve 13 that is opened and closed at a predetermined timing is disposed at the opening end of each exhaust port 11 on the combustion chamber 6 side (only one is disclosed in FIG. 1).

Each intake port 10 is connected to an intake passage 30. Although not shown, the intake passage 30 is provided with an air cleaner, an intake air amount sensor, a throttle valve, a surge tank, and the like sequentially from the upstream side to the downstream side. In the embodiment, the throttle valve is mechanically disconnected from the accelerator pedal, and its opening degree is electronically changed and controlled according to the accelerator opening degree. The surge tank is connected to each cylinder by an independent independent branch pipe (the intake passage 30 shown in FIG. 2 shows this independent branch pipe).

Each exhaust port 11 is connected to an exhaust passage 31. In this exhaust passage 31, as shown in FIG. 14, the linear oxygen sensor S6 as the air-fuel ratio sensor, the first three-way catalyst 71, the NOx absorption / reduction catalyst 72, the second third, are sequentially arranged from the upstream side to the downstream side. A source catalyst 73 and a linear oxygen sensor S6B are provided. The linear oxygen sensors S6 and S6B are used for detecting the air-fuel ratio based on the oxygen concentration in the exhaust gas, and can provide a linear output with respect to the oxygen concentration within a predetermined range including the theoretical air-fuel ratio. It is like that. However, as the air-fuel ratio sensor for air-fuel ratio control, the linear oxygen sensor S6 on the upstream side is used. The detection value of the downstream linear oxygen sensor S6B is also compared with the detection value of the upstream linear sensor S6, and is used to detect the exhaust gas purification state, the deterioration state of each catalyst, and the like. The NOx absorption / reduction catalyst 72 absorbs NOx in an atmosphere having a high oxygen concentration in the exhaust, while releasing NOx absorbed as the oxygen concentration decreases, and the released NOx is released by HC, CO, etc. in the exhaust. It is of the NOx absorption reduction type that reduces and purifies. Although the first three-way catalyst 71 and the NOx absorption / reduction catalyst 72 are separated from each other, the NOx absorption / reduction catalyst 72 and the second three-way catalyst 73 are close to each other. Is exclusively used for NOx release from the NOx absorption / reduction catalyst 72 and purification of harmful components after reduction.

In FIG. 14, a variable phase mechanism for changing the phase of the intake valve is indicated by reference numeral 81 (phase change between the crankshaft and the camshaft), and an actuator for the lift amount changing mechanism of the intake valve is indicated by reference numeral 82. . The mechanisms for changing the phase and lift amount are the same as those described in Patent Document 4 described above, and various such mechanisms have been proposed in the past (for example, intake air Detailed description of each mechanism will be omitted.

Referring again to FIG. 1, an ignition plug 16 is disposed at the upper portion of the combustion chamber 6 at the approximate center of the combustion chamber 6 surrounded by the four intake / exhaust ports 10 and 11 (four intake / exhaust valves 12 and 13). (See also FIG. 2). The electrode E at the tip of the spark plug 16 is at a position protruding from the ceiling of the combustion chamber 6 by a predetermined distance. Further, a fuel injection valve 18 is disposed at the peripheral edge of the combustion chamber 6 between the two intake ports 10 and below the intake ports 10. The fuel injection valve 18 is a multi-hole type fuel injection valve having a plurality of injection holes, specifically, six injection holes. The fuel injection direction of the fuel injection valve 18 is set in each nozzle so that the fuel spray injected from each nozzle is directed to the vicinity of the electrode E of the spark plug 16 and the upper side of the piston 5 as described later.

In FIG. 2, a swirl valve 40 is provided in association with one intake port 10A. That is, the two intake ports 10A and 10B are individually independent from each other by the partition 4a in the cylinder head 4, while the downstream end of the intake passage 30 (the downstream end of the independent branch pipe) is connected to the partition 4a. A continuous partition wall 30a is formed, and the two intake ports 10A and 10B are configured to be mutually independent passages by a predetermined distance from the combustion chamber 6 side toward the upstream side. The partition wall 30a is provided with a swirl valve 40 for changing the opening of one intake port 10A, and the swirl valve 40 is driven by an electromagnetic actuator 40a. Thus, when the swirl valve 40 is fully opened, the same amount of intake air is introduced from the two intake ports 10A and 10B, and the generation of the swirl in the combustion chamber 6 is not substantially performed. . By fully closing the swirl valve 40, intake air is supplied into the combustion chamber 6 only from the other intake port 10B, and intake swirl is generated in the combustion chamber 6 as shown by arrows in FIG. become. By adjusting the opening degree of the swirl valve 40, the strength of the swirl is changed.

As shown in FIG. 3, a fuel distribution pipe 19 common to all the cylinders 2 is connected to the base end portion of the fuel injection valve 18, and the fuel distribution pipe 19 is a high pressure supplied from a fuel supply system 20. The fuel is distributed and supplied to each cylinder 2. The fuel supply system 20 has a fuel passage 22 that connects the fuel distribution pipe 19 and the fuel tank 21, and the fuel passage 22 sequentially includes a low-pressure fuel pump 23, a low-pressure fuel pump 22 from the upstream side to the downstream side. A regulator 24, a fuel filter 25, a high-pressure fuel pump 26, and a high-pressure regulator 27 capable of adjusting the fuel pressure are connected. 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. Reference numeral 28 denotes a low-pressure regulator that adjusts the pressure state of the fuel returned to the fuel tank 21 side. 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.

FIG. 4 shows a control system for controlling the engine 1. In FIG. 4, reference numeral 50 denotes a controller (control unit) configured using a microcomputer. By this controller 50, an ignition circuit 17 (for ignition timing control), a fuel injection valve 18 (for fuel injection amount and fuel injection timing control), a high pressure regulator 27 (for fuel pressure adjustment) of the fuel supply system 20, and a swirl valve 40 (of In addition to controlling the actuator 40a), the electronically controlled throttle valve disposed in the intake passage 30, the phase changing mechanism 81 for the intake valve 12 and the lift amount changing actuator 82, which will be described later, are controlled. The controller 50 receives an engine speed signal from the engine speed sensor S1, an accelerator position signal from the accelerator position sensor S2, and an engine coolant temperature signal from the temperature sensor S3. The signal, the outside air temperature from the outside air temperature sensor S5, and the air fuel ratio signal from the air fuel ratio sensor S6 are input.

Next, the contents of control by the controller 50 will be described.
1. Fuel injection control In fuel injection control, a fuel injection control map is switched according to the engine temperature, and the control is performed according to the switched map. As the fuel injection control map, when the engine temperature is warm above a predetermined value (for example, 60 degrees C), the map during warm time shown in FIG. 5 is selected. The warm map is a stratified combustion region when the operating state of the engine is in a predetermined operating region of low load and low rotation, and a uniform combustion region in the other operating regions. In addition, the cold fuel injection control map is not shown in the figure, but is a uniform combustion region in all operation regions.

In the stratified combustion region, the fuel injection timing by the fuel injection valve 18 is set to a predetermined timing of the compression stroke, for example, in the case of batch injection, fuel is injected in a range of 0 ° to 60 ° before compression top dead center (BTDC), and ignition is performed. Stratified combustion is performed in which the air-fuel mixture is burnt in a state of being unevenly distributed in the vicinity of the plug 16. 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 in the intake stroke, fuel is injected from the fuel injection valve 18 and sufficiently mixed with the intake air to form a uniform mixture in the combustion chamber 6. Uniform combustion is performed to burn above. 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. When the engine is cold, as described above, uniform combustion is performed in the entire operation region (the air-fuel ratio is the stoichiometric air-fuel ratio or richer than that).

Further, in the high load range in the predetermined operation range that is the low rotation / low load range, as shown in FIG. 7, for example, split injection is performed in two stages. In the divided injection shown in FIG. 7, the start of the post-stage injection in which the fuel injection is performed at a later time is set in a range of, for example, BTDC 30 ° to 40 °, and the pre-stage injection in which the fuel injection is performed at an early time is Also, for example, the injection is started at a time about 40 degrees earlier in crank angle. Among the required fuel injection amounts in the predetermined operation region, the fuel amount injected in the subsequent injection is set to be a substantially constant amount, and the change in the fuel injection amount is the fuel injection amount in the previous injection. It is done by change. Note that the injection timing of the upstream injection can be set to the intake stroke.

2. 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. As the fuel pressure control map, when the engine temperature is a predetermined value (for example, 60 degrees C) or more, the map for the warm time shown in FIG. 6 is selected. In the map of FIG. 6, in the stratified combustion region, the fuel pressure is gradually increased as the engine speed increases (the minimum fuel pressure a1 is set to 12 MPa, for example, and the maximum fuel pressure a2 is set to 20 MPa, for example). . Further, in the uniform combustion region, a constant value of the maximum fuel pressure a2 in the stratified combustion region is always set to a constant value, and a fuel pressure increase accompanying an increase in engine speed is suppressed. When the engine temperature is colder than a predetermined value, the fuel pressure is always set to the fuel pressure corresponding to the maximum fuel pressure a2 in the stratified combustion region. Further, the fuel pressure at the time of starting the engine is, for example, about 0.5 MPa because the fuel pressure does not sufficiently increase because the high-pressure fuel pump 26 is driven by the camshaft.

3. The swirl valve 40 is opened and a swirl of intake air is generated in the combustion chamber 6 in a predetermined operation region that is a swirl control engine low rotation / low load region. In this case, the opening degree of the swirl valve 40 may be, for example, fully closed regardless of the engine load in the predetermined operating range, but it is always increased in the low load range (close to full opening). As the load increases, the opening degree is gradually reduced, and it can be set to be fully closed in a high load range.

Next, each nozzle hole of the fuel injection valve 18 will be described in detail with reference to FIGS. First, FIGS. 8 to 10 show states of fuel sprays injected from the injection ports of the fuel injection valve 18 as seen from different directions. FIG. 11 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. .

In FIG. 11, LB is an axis of the multi-hole type fuel injection valve 18, L1 to L6 are axes of the first to sixth nozzles, and A1 to A6 are sprays of fuel injected from the first to sixth nozzles. An angle E indicates an electrode of the spark plug. The nozzle diameters of all the nozzle holes are the same, for example, set to 0.15 mm. The fuel injection valve 18 is arranged so that the axis LB of the fuel injection valve 18 is positioned on the diametrical extension line of the cylinder 2 passing through the electrode E of the ignition plug 16 when viewed from the piston axial direction. In FIG. 11, a radial scale centered on the axis LB has an opening angle of 5 degrees, and a circumferential scale centered on the axis LB has an opening of 15 degrees. Shows corners.

The positional relationship of the axis of each nozzle will be described. First, the nozzles for stratifying the rich air-fuel mixture around the electrode E of the spark plug 16 are first to third nozzles. The first nozzle hole serves as a lower nozzle hole, and its axis L1 is arranged to be directed to a predetermined position below the electrode E from the axis LB. The axis L1 and the spray angle A1 of the first nozzle are located between the maximum lift positions of the two intake valves 12, that is, outside the movable range of the intake valves. Further, the second nozzle hole is a left nozzle hole, and its axis L2 is arranged so as to be directed to a predetermined position on the side (left side in the figure) in the vicinity of the electrode E from the axis LB. Further, the third nozzle hole is a right nozzle, and its axis L3 is arranged to be directed to a predetermined position on the side (right side in the figure) in the vicinity of the electrode E from the axis LB. 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 position of the intake valve 12. Thus, the respective axes of the first nozzle hole, the second nozzle hole, and the third nozzle hole are set so as to be directed to the vicinity of the electrode E and to surround the electrode E from below and from the left and right sides.

The fourth to sixth nozzle holes serve as piston-side nozzle holes, respectively, and perform fuel injection toward the piston top surface other than the vicinity of the electrode E. The axis L4 of the fourth nozzle hole is disposed so as to be directed from the axis LB to a predetermined position (left side in the figure) above the piston bottom dead center position on the piston side (lower side in the figure). The axis L5 of the fifth nozzle hole is a predetermined position above the piston bottom dead center position on the piston side (lower side in the figure) from the axis LB (a center position in the figure, a position directly below the axis L1 of the first nozzle hole). It is arranged to point to. The axis L6 of the sixth nozzle hole is arranged so as to be directed from the axis LB to a predetermined position (right side in the figure) above the piston bottom dead center position on the piston side (lower side in the figure). It should be noted that the entire fuel spray injected from all the injection holes is set so as to be within a conical space of 70 ° or less centering on the axis LB.

Of the three nozzles for injecting fuel spray around the electrode E, that is, the lower nozzle, the left nozzle, and the right nozzle, the fuel spray penetration of the lower nozzle is larger than the penetration from the left nozzle and the right nozzle. The axial length of the lower nozzle is set longer than the axial length of the left nozzle and the right nozzle. In addition, the axial length of each piston side nozzle hole which injects fuel spray other than around the electrode E is set to be the same as the axial length of the left nozzle hole and the axial length of the right nozzle hole. In addition to the above, the axis L1 of the lower nozzle among all the nozzles is set so as to be closest to the axis LB of the fuel injection valve 18, and the opening angle of the axis L1 with respect to the axis LB is also different from the above. It is set to be smaller than the opening angle of the axis L2 to L6 with respect to the axis LB at the nozzle hole.

As described above, since the axis lines 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 axis lines L4 to L6 of the fourth nozzle hole to the sixth nozzle hole are arranged on the piston side with respect to the axis line LB, the air-fuel mixture can be present in the entire combustion chamber 6, and the air-fuel mixture is homogeneous during uniform combustion. Can be improved. Further, since the axis lines L1 and L4 to L6 of the first nozzle hole and the fourth nozzle hole to the sixth nozzle hole are arranged outside the movable range of the intake valve 12, most of the nozzle holes are movable of the intake valve 12 while being multi-holes. It can arrange | position outside a range and can suppress that the fuel spray injected from each nozzle hole collides with the intake valve 12. FIG. The point of control for positive interference between the fuel spray from the left and right nozzles and the intake valve will be described later.

Here, the axes L1 to L3 of the first nozzle hole to the third nozzle hole arranged in the vicinity of the electrode E of the spark plug are set in the following relationship in order to obtain a mutual interference effect. That is, the first to third nozzle holes (the same applies to the fourth to sixth nozzle holes) are separated from the electrode E by 20 mm or more. Further, the opening angle between the axis L1 of the first nozzle hole and the axis L2 of the second nozzle is set to be in a range of 15 degrees to 25 degrees (20 degrees in the embodiment), and the axis L1 of the first nozzle hole The opening angle with the axis L3 of the third nozzle hole is set to be in a range of 15 degrees to 25 degrees (20 degrees in the embodiment). Thereby, the fuel spray from the first nozzle and the fuel spray from the second nozzle become continuous with each other in the vicinity of the electrode E due to the mutual interference effect. Similarly, the fuel spray from the first nozzle and the fuel spray from the third nozzle The fuel spray becomes continuous in the vicinity of the electrode E due to the mutual interference effect. In a state in which this mutual interference effect is obtained, in FIG. 11, in the vicinity of the electrode E, a continuous fuel spray extending from the axis L1 to L2 is generated and a continuous fuel spray extending from the axis L1 to the axis L3. Is generated (the shape of the continuous fuel spray in FIG. 11 is substantially V-shaped). By setting the fuel spray penetration from the lower nozzle hole to be larger than the fuel spray penetration from the left and right nozzles, the axis L1 approaches the electrode E from below by the mutual interference effect. The situation of being greatly moved in the direction is prevented or suppressed.

Here, since the in-cylinder pressure increases in the high load range in the low engine speed / low load range, the penetration of the fuel spray injected from each nozzle becomes small. This reduction in penetration means that the ratio of the fuel spray injected from the first to third nozzles particularly related to stratification passing through the electrode E toward the cylinder wall on the opposite side decreases. This means that the ratio of staying in the vicinity of E increases. Accordingly, by generating swirl in a predetermined operation region where stratification is performed, particularly in a high load region of the predetermined operation region, the rich mixture layer around the electrode E passes through the electrode E when viewed from the cylinder axial direction. In the direction perpendicular to the axis of the fuel injection valve, it moves and diffuses toward the swirl side, which is preferable in preventing the area around the electrode E from becoming excessively rich in this high load region. .

In order to prevent excessive enrichment around the electrode E described above, swirl generation is performed as described above, and divided injection is performed during the compression stroke. Due to the swirl generation, the rich mixture layer surrounding the electrode E is moved from the electrode E to the cylinder wall surface as a whole by the force of the swirl. What is the moving direction of the rich mixture layer around the electrode E? On the opposite side, the rich mixture layer is not located. Thereby, the initial combustion rate is reduced, and fuel efficiency is improved. In particular, the swirl strength is gradually increased as the engine load increases from the low load range in the low engine speed / low load range (the swirl valve opening is gradually decreased as the engine load increases). As a swirl of appropriate strength according to the increase in the fuel injection amount, the rich air-fuel mixture layer generated around the electrode E is brought into an optimum state in which fuel efficiency can be improved while ensuring ignitability. Can be set.

In addition to the above, by performing the above-described divided injection, a rich air-fuel mixture layer around the electrode E compared to a case where collective injection (for example, injection in which all the fuel injection amounts are executed at the subsequent injection timing in FIG. 7) is performed. Production can be further promoted. That is, even in the case of performing the same amount of fuel injection, in the case of split injection, the amount of fuel spray for the previous stage injection is considerably increased in the combustion chamber 6 during the period until the electrode E is energized (ignited). This ratio is diffused and hardly contributes to the generation of the rich mixture layer around the electrode E (only the fuel spray injected after the latter stage substantially contributes to the generation of the rich mixture layer around the electrode E). To do). The mixture concentration around the electrode E in the predetermined operating region where the engine is low and the load is low is set to be approximately the same as the mixture concentration around the electrode E in the low load region in the predetermined operating region. It is preferable to do this.

12 and 13 show an example of attachment of the fuel injection valve 18 to the cylinder head 4. In the figure, 45 is an attachment hole formed in the cylinder head 4, and FIG. 12 shows a state in which the attachment hole 45 is opened at the opening end surface to the outside of the cylinder head 4. On the outer end surface of the cylinder head 4, two positioning projections 4 c and 4 d are formed at the peripheral edge of the mounting hole 45. The distance between the two protrusions 4c and 4d (the distance between the opposing surfaces) is finished with high precision so as to be a predetermined dimension.

The fuel injection valve 18 has a cylindrical portion 18c that is inserted into the mounting hole 45 without rattling, and a protruding portion 18d that extends substantially in the radial direction from the proximal end portion of the cylindrical portion 18c, and the tip of the protruding portion 18d. The portion is a connection terminal portion 18e to which an externally energizing coupler is detachably connected. In the embodiment, the cylindrical portion 18c and the protruding portion 18d are integrally formed (except for the electrical connection portion). However, the protruding portion 18d is formed separately from the cylindrical portion 18c, and is later circumferentially connected to each other. Alternatively, the cylinder portion 18c may be integrally assembled in a state of being restricted so as not to move in the axial direction.

The fuel injection valve 18 is attached to the cylinder head 4 by inserting the cylinder portion 18c into the attachment hole 45 to a predetermined depth. At this time, the protrusion 18 c of the fuel injection valve 18 is positioned (sandwiched) between the pair of protrusions 4 c and 4 d formed on the cylinder head 4. The width of the c projection 18c of the fuel injection valve 18 is accurately finished corresponding to the dimension between the pair of projections 4c and 4d, and the projection 18c is between the pair of projections 4c and 4d. Insertion is made without rattling (this state is the state of FIG. 13). And in the attachment state of FIG. 13, the positional relationship with respect to the electrode E of each nozzle is set so that it may be in the state of FIG. As described above, the protrusion 18c of the fuel injection valve 18 and the pair of protrusions 4c and 4d formed on the cylinder head 4 allow the fuel injection valve 18 to be attached to the cylinder head 4 with a predetermined mounting angle (rotation angle). It also functions as a positioning (tool for use) for mounting. As described above, since the axis L1 of the lower injection port is located closest to the axis LB of the fuel injection valve 18, when the fuel injection valve 18 is rotated in the circumferential direction from the attached state to the engine, the axis line The amount of fluctuation of the distance in the vertical direction with respect to the electrode E of L1 is the smallest on the axis L1 compared to the other axes L2 to L6. That is, this is a preferable setting in order to make the vertical distance between the axis L1 and the electrode E as constant as possible.

FIGS. 15 and 16 show examples of changing the valve opening characteristics of the intake valve. FIG. 15 shows a case for warm time, and FIG. 16 shows a case for cold time. In FIG. 15 which is for warm use, the valve opening characteristics are changed stepwise (or continuously variable) depending on the temperature, as indicated by B1 to B6. B6 is a basic characteristic, and is opened near the intake top dead center and closed near the intake bottom dead center. As the temperature decreases, the intake air is quickly closed (the valve opening timing is set to be the same at B1 to B6). When the lift amount of the intake valve 12 is in the range between δ1 and δ2, it is the timing at which fuel spray from the left and right nozzles directed near the left and right of the electrode E collides with the intake valve 12. During warm weather, the problem of a large amount of fuel spray adhering to the inner wall surface of the cylinder is unlikely to occur, and the temperature inside the cylinder is high, and vaporization and atomization of the fuel spray are promoted on the way. The timing is such that it does not collide with the valve 12. Note that the fuel injection timing shown in FIG. 15 is merely an example, and the fuel injection timing can be changed according to the change of the valve opening characteristic in order to avoid collision between the fuel spray and the intake valve 12 (divided injection). Is also possible).

In FIG. 16 used for cold weather, it is used when the outside air temperature is 0 ° C. or less, for example. The valve opening characteristics for the cold state are C1 to C3 indicated by a solid line. When the temperature is changed stepwise (may be a continuously variable type) according to the temperature and the temperature exceeds a certain level, the valve opening for the warm state is performed. The characteristics are shifted to the characteristics (in FIG. 16, the valve opening characteristics B4 to B6 for warm conditions are indicated by broken lines). The valve opening characteristics in the cold state are the intake late opening that is opened at a time greatly delayed from the intake top dead center, and the valve closing timings are all at the same time near the intake bottom dead center. Is set. When the lift amount of the intake valve 12 is in the range between δ1 and δ2, it is the timing at which fuel spray from the left and right nozzles directed near the left and right of the electrode E collides with the intake valve 12. FIG. 5 shows a state in which the engine is warmed up after the engine is started in a low load region during cold, that is, when the outside air temperature is low (for example, when the engine coolant temperature is 20 ° C. or lower). In the low load region as shown in FIG. 4, the fuel injection is set to be performed when the fuel spray from the left and right nozzles collides with the intake valve 12 (crank angle). In particular, when the valve opening characteristic C1 is selected when it is extremely cold (for example, −20 ° C. or less), the fuel is sprayed at the timing when the fuel spray collides with the intake valve 12 when the intake valve 12 is at the maximum lift position. It is set to perform injection. Of course, according to the change of the valve opening characteristic, the fuel injection timing can be changed so as to collide with the intake valve 12 for a sufficiently long period of time. For this reason, the fuel injection timing can be divided injection. (For example, when the valve opening characteristic C3 is selected, the injection is divided into the first valve opening period and the second valve opening period of the intake valve 12).

Next, referring to the flowchart shown in FIG. 17, an example of control when fuel spray collides with the intake valve 12 will be described. This flowchart is used when the engine is cold and the outside air temperature is a predetermined temperature or less. The engine starts at In the following description, R represents a step. First, in R71, it is determined whether or not the engine has completely exploded by an engine start operation (drive by a starter motor). The determination at R71 is performed, for example, by checking whether the engine speed has reached a predetermined speed (for example, 500 rpm) or more. When the determination of R71 is NO, the determination of R71 is repeated, and when the determination of R71 is YES, the temperature increase control is performed at R72. This temperature increase control is a uniform combustion that becomes fuel injection in the intake stroke, but is a control that raises the exhaust gas temperature in order to activate the exhaust gas purification catalyst at an early stage, and greatly increases the ignition timing. Control. This temperature increase control is performed for a predetermined period (for example, 10 to 20 seconds), and the engine (intake valve 12) is also heated earlier by this temperature increase control.

After R72, in R73, it is determined whether or not the low load range shown in FIG. When the determination in R73 is YES, interference control is performed in R74. As described above, this interference control is a control in which fuel sprays from the left and right nozzles actively collide with the intake valve 12 (the valve opening characteristics of the intake valve 12 are C1 to C3 in FIG. 16). Since it is after the temperature increase control in R72 is executed, the intake valve 12 is also heated considerably, and the vaporization and atomization of the fuel spray colliding with the intake valve 12 is accelerated accordingly. After R74, it is determined in R75 whether or not the engine has been warmed up (for example, whether or not the engine coolant temperature has become 30 ° C. or higher). If the determination in R75 is NO, the process returns to R73. And when it becomes YES by determination of R75, it transfers to R76 and normal control is performed as demonstrated about FIG. 5 (When the whole area uniform combustion is performed according to cooling water temperature, It is distinguished from the case of following the map of FIG.

If the determination in R73 is NO, in R77, after uniform combustion is performed, the routine proceeds to R75. However, since the process in R77 is before the engine is warmed up, the ignition timing is slightly retarded (the retard amount is smaller than the retard amount in R72), and the engine is warmed up.

Although the embodiment has been described above, the present invention is not limited to this, and various modifications can be made within the scope described in the scope of claims. For example, the present invention includes the following cases. The number of nozzle holes of the fuel injection valve 18 (18B) may be 5 or 7 or more. In order to suppress the formation of the rich air-fuel mixture around the electrode E, only one of the swirl generation and the split injection in the compression stroke may be performed without generating the swirl. There may be. The present invention can be applied not only to a four-cylinder engine but also to a multi-cylinder engine having two or more cylinders. The settings (diameter and length) of each nozzle can be set as appropriate, and the diameter and length of all nozzles can be set to the same setting. The fuel injection may be performed only in the latter half of the compression stroke in the entire stratified combustion region. The valve opening characteristic of the intake valve 12 may be always set to the same value (fixed to the basic valve opening characteristic). You may make it perform interference control by R74 also in a high load area (especially the load area below the low load area in a uniform combustion area). Of course, the object of the present invention also implicitly includes providing an invention that is substantially preferred or expressed as an advantage.

The principal part side surface sectional view showing an example of the engine to which the present invention was applied. The simplified top view of the combustion chamber vicinity containing a swirl production | generation part. The system diagram which shows the fuel system example. The figure which shows an example of a control system in a block diagram. The figure which shows the example of a setting of a stratified combustion area | region and a uniform combustion area | region. The figure which shows the example of a setting of the fuel pressure change according to an engine speed change. The figure which shows an example of division | segmentation injection. The perspective view which shows the state of the fuel spray injected from a some nozzle. The figure seen from the side which shows the state of the fuel spray injected from multiple nozzle holes. The figure seen from the opposite side of the fuel injection valve which shows the state of the fuel spray injected from multiple injection holes. The figure which shows the detail of the example of a setting of multiple injection holes, and is seen from the axial direction of a fuel injection valve. The perspective view which shows the example of attachment of the fuel injection valve with respect to a cylinder head, and shows the state just before attachment. The perspective view which shows the example of attachment of the fuel injection valve with respect to a cylinder head, and shows an attachment completion state. The figure which shows simply the structural example of an exhaust passage, and a valve opening characteristic change mechanism. The figure which shows the example of a valve opening characteristic change of the intake valve at the time of warm. The figure which shows the example of a valve opening characteristic change of the intake valve at the time of cold. The flowchart which shows the example of control of this invention.

1: Engine 3: Cylinder block 4: Cylinder head 5: Piston 6: Combustion chamber 10 (10A, 10B): Intake port 12: Intake valve 16: Ignition valve 17: Ignition circuit 18: Fuel injection valve 50: Controller (fuel injection Control means, valve opening characteristic control means)
E: Spark plug electrode LB: Fuel injection valve axis L1: First injection port (lower injection port) axis A1: Spray angle of fuel injected from the first injection port (lower injection port) L2: Second injection port (left side) Axis A2 of the nozzle): spray angle of fuel injected from the second nozzle (left nozzle) L3: axis A3 of the third nozzle (right nozzle) A3: spray angle 81 of the fuel injected from the third nozzle (right nozzle) : Intake valve phase change mechanism (Valve opening characteristic change means)
82: Actuator for changing lift amount of intake valve (lift amount changing means)

Claims (7)

For each cylinder, two intake valves, a spark plug disposed so that an electrode is positioned at substantially the center of the combustion chamber, and a combustion chamber peripheral portion between the two intake valves in a plan view. And a multi-hole fuel injection valve having a plurality of injection holes for directly injecting fuel into the combustion chamber,
As the plurality of nozzle holes, at least a left nozzle hole directed near the left side of the electrode, a right nozzle hole directed near the right side of the electrode, and a lower nozzle hole directed near an extension line near the tip of the electrode In a spark ignition direct injection engine set to have
The spray angle from the right nozzle and the spray angle from the left nozzle are respectively set to be within the movable range of the intake valve, while the spray angle from the lower nozzle is outside the movable range of the intake valve. Is set to be
Set so that fuel injection is performed at the timing when fuel spray from the left and right nozzles collides with the intake valve in the predetermined operating range, which is a low load range before engine warm-up. Being
This is a spark ignition direct injection engine. In claim 1,
A spark ignition direct injection engine characterized in that the intake valve is opened slowly at a position that is greatly delayed from the intake top dead center in the intake stroke during the predetermined operating range. In claim 1 or claim 2,
In the predetermined operation region after the temperature increase control for positively raising the exhaust gas temperature by retarding the ignition timing greatly after starting the engine, the fuel spray from the left and right nozzles collides with the intake valves. A spark ignition direct injection engine characterized in that the fuel injection is performed. In claim 2,
A spark ignition type direct injection engine characterized in that, in the predetermined operating region, a closing timing of an intake valve that is slowly opened is set to a substantially intake bottom dead center position. In claim 4,
The spark ignition direct injection engine characterized in that, in the predetermined operating region, the valve opening timing of the intake valve gradually approaches the intake top dead center as the engine temperature rises, and the valve opening period is extended. In claim 1,
A spark ignition direct injection engine, wherein fuel injection is performed so that fuel spray from the left and right injection ports collides with an intake valve at least in a maximum lift position in the predetermined operation region. In any one of Claims 1 thru | or 6,
Length of the front Symbol lower injection port, from the injection port of the left side opening and right side injection port until the electrode is set to more than 20 mm,
The opening angle formed between the lower nozzle hole and the left nozzle hole is set in a range of 15 degrees to 25 degrees, and fuel spray from the lower nozzle hole is generated in a predetermined operation region that is a low rotation / low load region of the engine. The fuel spray from the left nozzle is set to be continuous with each other by the mutual interference effect,
An opening angle between the lower nozzle and the right nozzle is set in a range of 15 to 25 degrees, and the fuel spray from the lower nozzle and the fuel spray from the right nozzle are mutually in the predetermined operation region. Set to be continuous with each other due to interference effects,
This is a spark ignition direct injection engine.

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