JP2007177740A - Spark-ignition direct-injection engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent fuel spray from left and right injection holes directed into the vicinity of an electrode of an ignition plug, from interfering (colliding) with intake valves. <P>SOLUTION: A fuel injection valve 18 is disposed at the peripheral edge part of a combustion chamber and between two intake valves 12 from the top view. The left injection hole (an axis L2) and the right injection hole (an axis L3) of the fuel injection valve 18 are directed to the left and right near the electrode E of the ignition plug 16 projected into the combustion chamber 6. Fuel injection is carried out in a basic injection period in which the intake valves 12 are near the maximum lift quantity. Interference between the fuel spray and the intake valves 12 is thereby prevented. As for a specific cylinder causing the interference by a manufacturing error of the ignition plug 16 or fuel injection valve 18, fuel injection is carried out in the valve opening first half period or valve opening second half period of the intake valves 12 which is timing not causing interference, while limiting (reducing or forbidding) fuel injection in the basic injection period. <P>COPYRIGHT: (C)2007,JPO&INPIT

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, in the fuel injection valve disposed between the two intake valves at the periphery of the combustion chamber and in plan view, when fuel injection is performed in the intake stroke, the fuel injection valve is directed to the left and right sides in the vicinity of the electrodes. There are times when the fuel spray from the left and right nozzles interferes with the intake valve. That is, in an intake valve set to a normal valve opening characteristic that is opened near the intake top dead center and closed near the intake top dead center, the intake valve is in a high lift state during the high lift state. If the intake valve is in a lift amount other than the above (when the intake valve is in a medium lift amount state), there is no interference in the first and second valve opening periods when the valve is in a low lift state. The fuel spray and the intake valve will interfere with each other. Normally, when fuel injection is performed during the intake stroke, fuel vaporization and atomization are required to be accelerated. Therefore, fuel injection is performed during the middle of the valve opening when the intake valve is in a high lift state. In other words, when the intake valve is in a high lift state, the piston speed is sufficiently increased and the intake flow is fast, so that the rapid intake flow is effectively utilized to promote fuel vaporization and atomization. For this reason, fuel injection is performed when the intake valve is in a high lift state. In addition, if the said interference arises, it will cause a smoke and NOx increase.

  By the way, the fuel injection valve has a manufacturing error. For example, the fuel injection valve has a slight manufacturing error, for example, an error of about ± 3.5 degrees in the opening angle between the axis of the fuel injection valve and the axis of each nozzle. is there. Therefore, when fuel injection is performed in the intake stroke, due to manufacturing errors of the fuel injection valve, even if fuel injection is performed in the middle of the valve opening when the intake valve is in a high lift state due to manufacturing errors of the fuel injection valve, The fuel spray may interfere with the intake valve.

  The problem of interference between the fuel spray from the left and right nozzles and the intake valve when performing fuel injection in the intake stroke described above also occurs when the valve opening characteristic of the intake valve is changed. In other words, in order to reduce pumping loss (further improvement in fuel consumption), the intake valve closing timing is based on the normal valve opening characteristics when the intake valve is closed earlier than the intake bottom dead center, or vice versa. If the intake valve is closed at a time much later than the intake bottom dead center, the fuel injection is performed at the same time as the normal valve opening characteristics. Will interfere.

  The present invention has been made in view of the above circumstances, and its purpose is spark ignition that can prevent interference between the fuel spray from the left and right injection nozzles directed to the left and right in the vicinity of the electrode and the intake valve. It is to provide a direct injection engine.

To achieve the above object, the following first 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,
In the spark ignition direct injection engine set to have at least a left-side nozzle directed to the left side of the electrode and a right-side nozzle directed to the right side of the electrode as the plurality of nozzles,
Basic injection timing setting means for setting, as a basic injection timing, a valve opening middle period in which the intake valve is in a high lift state in an intake stroke injection region in which fuel injection is performed in the intake stroke;
Interference detecting means for detecting interference between the fuel spray from the left and right nozzles and the intake valve when fuel injection is performed at the basic injection timing;
In the intake stroke injection region, the fuel injection timing for the specific cylinder in which the interference is detected by the interference detection means is limited so that the fuel injection at the basic injection timing does not cause the interference. Injection timing changing means for performing fuel injection during at least one of the first and second valve opening periods in a low lift state;
It is supposed to be equipped with.

  According to the above-described solution technique, if fuel injection is performed at the basic injection timing, the middle stage of valve opening in which the intake valve is in a high lift state for a specific cylinder in which the fuel spray from the left and right injection ports interferes with the intake valve The fuel injection timing is limited so as not to interfere with the fuel injection at the fuel injection timing and at least one of the first and second valve opening periods when the intake valve is in the low lift state, that is, the time when there is no interference. Therefore, interference between the fuel spray and the intake valve is prevented while securing a predetermined fuel injection amount.

A preferred mode based on the first solution is as set forth in claims 2 to 7 in the claims. That is,
The restriction of fuel injection at the basic injection timing by the injection timing changing means is performed by allowing the fuel injection to be performed only during a narrow period when the intake valve is in a higher lift state. Correspondence). In this case, interference can be prevented while performing fuel injection in the middle of the valve opening, which is optimal as a fuel injection timing with a large intake flow.

  The restriction of fuel injection at the basic injection timing by the injection timing changing means is performed by prohibiting fuel injection in the middle of the valve opening when the intake valve is in a high lift state. ). In this case, it is preferable to prevent interference easily and reliably.

  The fuel injection after the change by the injection timing changing means is at least two of the three periods of the valve opening middle period when the intake valve is in the high lift state and the valve opening early period and the valve opening late period when the intake valve is in the low lift state. The divided injection is executed in a period (corresponding to claim 4). In this case, it is preferable to ensure the predetermined fuel injection amount by executing the fuel injection in a plurality of periods.

Split injection of post-stage injection in which fuel injection is performed during the compression stroke and pre-stage injection in which fuel injection is performed during the intake stroke in a high load range where stratified combustion is performed so that the local air-fuel ratio around the electrode becomes rich Is set to do
The pre-stage injection in the specific cylinder is performed in at least one period of a middle period when the intake valve is in a high lift state or a late stage when the intake valve is in a low lift state.
(Corresponding to claim 5). In this case, stratification in which the local air-fuel ratio around the electrode is appropriately enriched by the post-injection can be reliably obtained. Further, by setting the injection timing of the pre-stage injection, it is possible to sufficiently promote the vaporization and atomization of the fuel necessary for securing the output. In addition, since the fuel injection amount required for the pre-stage injection is small, the fuel injection is completed in a small crank angle range in which the lift amount is extremely large even in the middle of the opening of the intake valve. It can be made not to interfere with fuel spray.

Depending on the operating state of the engine, a stratified combustion region in which fuel injection is performed at least in the compression stroke so that the local air-fuel ratio around the electrode becomes rich, and a higher load and higher rotation than the stratified combustion region in the intake stroke Three regions are set: a uniform combustion region in which only fuel injection is performed, and a transition region in which fuel injection is performed in the compression stroke and the intake stroke as a boundary region between the stratified combustion region and the uniform combustion region,
In the transition region, the fuel injection in the intake stroke for the specific cylinder is at least one period of three periods of a middle period of opening of the intake valve when the intake valve is in a high lift state, a first period of opening of the valve during a low lift state, and a late period of opening the valve. Done in
(Corresponding to claim 6). In this case, the transition between the stratified combustion region and the uniform combustion region can be smoothly performed by setting the transition region. And in a transition area | region, it becomes preferable when vaporization of fuel spray and atomization are fully accelerated | stimulated. Since the fuel injection amount is small, the fuel injection is completed in a small crank angle range where the lift amount is extremely large even in the middle of the opening of the intake valve so that the intake valve and the fuel spray do not interfere with each other. Can be.

  In a uniform combustion region in which fuel injection is performed only in the intake stroke and the in-cylinder air-fuel ratio is rich (λ ≦ 1) below the stoichiometric air-fuel ratio, fuel injection for the specific cylinder is performed in a high lift state of the intake valve The split injection is performed in at least two periods among the three periods of the middle valve opening period, the first valve opening period in the low lift state, and the second valve opening period (corresponding to claim 7). In this case, the fuel injection amount increases, but the fuel injection is completed in a small crank angle range where the lift amount is extremely large even in the middle of the opening of the intake valve by the divided injection divided into at least two periods. Thus, the intake valve and the fuel spray can be prevented from interfering with each other.

In order to achieve the above object, the following second solution is adopted in the present invention. That is, as described in claim 8 in the claims, for each cylinder, two intake valves, an ignition plug disposed so that an electrode is positioned at a substantially central portion of the combustion chamber, and a plan view A multi-hole type fuel injection valve having a plurality of injection holes disposed on the periphery of the combustion chamber between the two intake valves and directly injecting fuel into the combustion chamber;
In the spark ignition direct injection engine set to have at least a left-side nozzle directed to the left side of the electrode and a right-side nozzle directed to the right side of the electrode as the plurality of nozzles,
Stratified combustion in which fuel injection is performed at least in the intake stroke so that the local air-fuel ratio around the electrode is rich in a high-load region in which fuel injection is performed in at least the compression stroke or in-cylinder air-fuel ratio is uniform. In the low load range in the region, the intake valve close timing is set to a predetermined crank angle before the intake bottom dead center so that the effective compression ratio becomes small,
Fuel injection is performed in at least one of the two periods of the first and second valve opening periods when the intake valve is in a low lift state.
It is like that. According to the above solution, fuel efficiency is improved by reducing the pumping loss due to early closing of the intake air, and fuel spray vaporization and atomization are promoted by preventing the fuel spray and the intake valve from interfering with each other by appropriately setting the fuel injection timing. Thus, smoke and NOx can be reduced.

In order to achieve the above object, the following third solution is adopted in the present invention. That is, as described in claim 9 in the claims, for each cylinder, two intake valves, a spark plug disposed so that an electrode is positioned substantially at the center of the combustion chamber, and in plan view A multi-hole type fuel injection valve having a plurality of injection holes disposed on the periphery of the combustion chamber between the two intake valves and directly injecting fuel into the combustion chamber;
In the spark ignition direct injection engine set to have at least a left-side nozzle directed to the left side of the electrode and a right-side nozzle directed to the right side of the electrode as the plurality of nozzles,
Stratified combustion in which fuel injection is performed at least in the intake stroke so that the in-cylinder air-fuel ratio is uniform, and a high load region in the stratified combustion region in which fuel injection is performed at least in the compression stroke so that the local air-fuel ratio around the electrode becomes rich In the low load region in the region, the intake valve closing timing is determined to be after the predetermined crank angle from the intake bottom dead center so that the effective compression ratio becomes small,
Fuel injection is performed in at least one of the two periods of the valve opening middle period in which the intake valve is in a high lift state and the compression stroke.
It is like that. According to the above solution, fuel efficiency is improved by reducing pumping loss due to late intake closing, and fuel spray vaporization and atomization are promoted by preventing fuel spray and intake valve from interfering with appropriate settings of fuel injection timing. Thus, smoke and NOx can be reduced.

A preferred mode based on each of the above solutions is as set forth in claim 10 in the claims. That is,
As a nozzle directed to the vicinity of the electrode, it has a lower nozzle directed to the extension near the tip of the electrode,
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 10). 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, interference between the fuel spray and the intake valve can be prevented, and as a result, smoke and NOx reduction can be achieved.

  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 is 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 air-fuel ratio sensor (configured by the linear oxygen sensor described above) S6 provided in the exhaust passage, and the magnitude of the ion current detected by the ion current detection circuit 42 described later 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. Further, the injection timing of the front injection can be set to the intake stroke. The setting (change) of the fuel injection timing (fuel injection mode) related to the interference between the fuel spray and the intake valve will be described later.

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. Swirl Control In a predetermined operation region that is an engine low speed / low load region, the swirl valve 40 is opened and intake swirl is generated in the combustion chamber 6. 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 nozzle holes that inject fuel spray around the electrode E, that is, the lower nozzle hole, the left nozzle hole, and the right nozzle hole, the fuel spray penetration of the lower nozzle hole is larger than the penetration from the left nozzle hole and the right nozzle hole. 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. Note that the setting (change) of the fuel injection timing for preventing 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 a method for detecting whether or not the electrode E and the fuel spray from the left and right nozzles interfere (collision), and the ionic current flowing through the electrodes (center electrode and peripheral electrodes). The method of discriminating the presence or absence of interference according to the size of the image is shown. That is, the magnitude of the ionic current changes according to the magnitude of the local air-fuel ratio around the electrode, but when fuel is injected at a predetermined time in the intake stroke, interference between the fuel spray and the intake valve occurs. Compared to the case where no interference occurs, the local air-fuel ratio around the electrode is considerably leaner. Therefore, by observing the magnitude of the ion current (for example, see the magnitude relationship with a predetermined threshold) ), The presence or absence of interference can be determined.

  First, the spark plug 16 has a peripheral electrode grounded via the engine 1 and a center electrode connected to the ignition circuit 17 as is known. Between the ignition circuit 17 and the ignition plug 16, a current detection circuit 42 for detecting an ionic current is provided. The current detection circuit 42 includes a backflow prevention diode 42 a that allows only a current flow from the ignition circuit 17 toward the spark plug 16. The current detection circuit 42 includes a backflow prevention diode 42b, a reference voltage source 42c, and a resistor 42d connected in series to each other on the spark plug 16 side of the backflow prevention diode 42a. The spark plug 16 is grounded through 42d. Furthermore, the current detection circuit 42 includes a voltmeter 42e that detects a voltage between the resistors 42c.

  When the engine 1 is operated, immediately after performing fuel injection in the intake stroke (fuel injection in the middle of the valve opening when the intake valve is in a high lift state as will be described later), the fuel spray existing around the electrode causes the central electrode to An ionic current flows between the peripheral electrodes, and a voltage corresponding to the magnitude of the ionic current is detected by the voltmeter 42e (the larger the detected voltage, the larger the ionic current). The ionic current changes as shown in FIG. 16 due to the change in the air-fuel ratio of the air-fuel mixture around the electrode E. Although the magnitude of the detected ion current (stored ion current or voltage) is slightly changed, the maximum value among the detected values is detected and stored. Assuming that the air-fuel ratio of the air-fuel mixture is leaner than the stoichiometric air-fuel ratio, the larger the detected ion current, the richer the air-fuel ratio (or vice versa if the air-fuel ratio is richer than the stoichiometric air-fuel ratio). . In this way, the ion current (that is, the presence or absence of interference) is detected and stored for each cylinder (at least the cylinder causing the interference is stored). Whether the air-fuel ratio of the air-fuel mixture is leaner or richer than the stoichiometric air-fuel ratio is detected, for example, when the air-fuel ratio is corrected to be leaner than the current value (when the fuel injection amount is corrected to decrease). It is understood that the current air-fuel ratio is leaner than the stoichiometric air-fuel ratio if the ion current value to be reduced is smaller, and the current air-fuel ratio is richer than the stoichiometric air-fuel ratio if the detected ion current value is increased. Is done. The ion current detection may be performed when the engine is in a steady operation state.

  The above-described current detection circuit 42 may be provided individually for each cylinder (each spark plug 16), but the ion current detection circuit 42 can also be used for each cylinder (the timing for detecting the ion current is different for each cylinder). It can be shared because it differs between cylinders). Further, without shipping the engine in a state where the ion current detection circuit 42 is mounted, the ion current detection circuit 42 is incorporated in the engine, for example, at the final inspection stage in the engine assembly factory, and the above-described ion current detection and storage is performed. Then, the ion current detection circuit 42 may be removed from the engine (the cost will be greatly reduced).

  FIG. 17 uses a resistance detection circuit 43 in place of the current detection circuit 42. The same components as those in FIG. In the present embodiment, the ammeter 43a is incorporated in series with the resistor 42d and the like, and the current may be detected by the ammeter 43a at the timing immediately before ignition (a state in which air-fuel mixture exists around the electrodes). The detected current corresponds to the insulation resistance between the center electrode and the peripheral electrode, and this insulation resistance becomes smaller as the air-fuel ratio of the air-fuel mixture around the electrode becomes richer. That is, it is determined that interference occurs when the local air-fuel ratio around the electrode is considerably lean and the insulation resistance is large.

  Next, the point of interference between the fuel spray (fuel spray from the left and right nozzles) and the intake valve will be described. First, FIG. 18 shows a case where the valve opening characteristic of the intake valve 12 is a basic characteristic. In this basic characteristic, as is generally done, the intake valve 12 is opened near the intake top dead center (a little earlier than the intake top dead center), and near the intake bottom dead center (from the intake bottom dead center). Is closed at a later time). When the lift amount of the intake valve 12 is located in a region between δ1 and δ2 in FIG. 18, the designed fuel spray and the intake valve 12 cause interference. As understood from FIG. 18, the interference does not occur in the first valve opening period (a period before c1), the middle valve opening period (a period between c2 and c3), and the opening period. This is the late valve period (time later than c4), and interference occurs between c1 and c2 and between c3 and c4. The basic fuel injection timing in the intake stroke is the middle of the valve opening. This is because the fuel spray is sufficiently promoted to vaporize and atomize by performing the fuel injection when the piston speed is increased and the intake flow is sufficiently increased. The fuel injection in the middle of the valve opening is indicated by the symbol JB.

  When the fuel injection JB is performed in the middle of the valve opening, c2 and c3 are brought close to each other due to the positional deviation of the left and right nozzles due to a manufacturing error, and the fuel injection JB is executed as it is. May end up. The presence or absence of interference can be determined by the above-described ion current detection or insulation resistance detection. When there is a specific cylinder that causes interference, the fuel injection timing in the intake stroke of this specific cylinder is changed as follows. That is, first, the fuel injection JB in the middle of the valve opening that causes interference is limited so as not to cause interference. This restriction is performed by at least one of delaying the start timing of injection and accelerating the end timing of injection while executing fuel injection in the middle period of valve opening, but it is preferable to perform both. This is the fuel injection amount reduction correction at the same time.) When performing such a restriction, the crank angle at which the intake valve 12 is at the maximum lift position is set as a reference crank angle, and fuel injection is started at a start time that is a predetermined crank angle CK before the reference crank angle. The fuel injection is terminated at the end timing after CK, and the crank angle range of 2CK, which is the range between the fuel injection start timing and the end timing, is limited to a sufficiently small range for preventing interference. Is preferred. Further, instead of the above-described restriction, the restriction content may be set to prohibit fuel injection in the middle of the valve opening (the fuel injection amount in the middle of the valve opening is 0).

  The insufficient fuel injection amount caused by the restriction in the middle of the valve opening is compensated by executing the fuel injection in at least one of the middle period of the valve opening or the late stage of the valve opening. The fuel injection for this compensation is preferably performed in the first half of the valve opening in consideration of vaporization and atomization promotion of the fuel spray, and may be performed in the latter half of the valve opening when priority is not given to vaporization and atomization promotion. Of course, fuel injection may be performed in both the first and second valve opening periods. In particular, when fuel injection is not performed in the middle valve opening period, fuel injection is performed in both the first and second valve opening periods. This is preferable in ensuring a predetermined fuel injection amount. From the viewpoint of ensuring a predetermined fuel injection amount, it is preferable to perform split injection in at least two periods out of the three periods of the middle valve opening period, the first valve opening period, and the second valve opening period. In the case where fuel injection is performed in all of the two periods, even a very large amount of fuel injection is reliably ensured. In order to reliably prevent interference in consideration of manufacturing errors of the fuel injection valve 18, the fuel injection in the first half of the valve opening is terminated at a time sufficiently earlier than c1, and the fuel injection in the second half of the valve opening is performed more than C4. It is set to start at a sufficiently late time.

  In the high load region in the stratified combustion region shown in FIG. 5, since the fuel injection amount is relatively large, it is divided into post injection in the latter half of the compression stroke and pre-injection in the first half of the compression stroke. It is also possible to perform the pre-injection in the intake stroke. In this case, for a specific cylinder that causes interference, fuel injection in the intake stroke can be performed at least in the middle of the valve opening or in the latter half of the valve opening. However, it is preferable from the viewpoint of securing a necessary amount of fuel injection (because fuel spray vaporization and atomization promotion are not emphasized as compared with the case of uniform combustion).

  Here, as indicated by a broken line in FIG. 5, a transition region may be set between the stratified combustion region and the uniform combustion region. The transition region is for smoothly shifting the fuel injection mode between the stratified combustion region and the uniform combustion region. Basically, both the fuel injection in the compression stroke and the fuel injection in the intake stroke are performed. Is called. In the transition region, as the stratified combustion region approaches the uniform combustion region, the fuel injection amount in the compression stroke is gradually reduced, and the fuel injection amount in the intake stroke is increased by this amount (from the uniform combustion region to the stratified combustion region). Vice versa) In the transition region, for a specific cylinder that causes interference, fuel injection in the intake stroke is performed in at least one of the three periods of the middle valve opening period, the first valve opening period, and the second valve opening period. The fuel injection in the latter half of the valve opening can be gradually changed to the fuel injection in the middle of the valve opening or the first half of the valve opening as it approaches the uniform combustion region.

  In a uniform combustion region where fuel injection is performed only in the intake stroke, the in-cylinder air-fuel ratio is rich (λ ≦ 1) below the stoichiometric air-fuel ratio, and a large amount of fuel injection is required. In such a uniform combustion region, the specific cylinder that causes interference may be divided injection in which fuel injection is performed in at least two periods among the three periods of the middle valve opening period, the first valve opening period, and the second valve opening period. Preferably (fuel injection in the middle of the valve opening is given the above-mentioned limitations to prevent interference).

  FIG. 19 shows another embodiment of the present invention, which is a case where the intake air is quickly closed to reduce the pumping loss. Note that this embodiment is not a fuel injection mode for a part of the specific cylinders, but a fuel injection mode common to all cylinders. In the present embodiment, the valve opening characteristic of the intake valve 12 is changed from the basic characteristic of FIG. 18, the valve closing timing is set to a timing that is considerably earlier than the intake bottom dead center, and the lift amount is also the basic characteristic. It is set to be smaller than in the case of. The region in which the intake air is quickly closed is a high load region in the stratified combustion region shown in FIG. 5 or a low load region in the uniform combustion region (even if the transition region is set, even in the transition region). Good).

  When the intake valve is closed early, the intake valve 12 and the fuel spray always interfere with each other in the middle of the valve opening when the intake valve 12 is in a high lift state. Therefore, in the present embodiment, fuel injection is executed in at least one of the two periods of the first and second valve opening periods. In the stratified charge combustion region, it is preferable to inject fuel in the latter half of the valve opening in order to form a rich air-fuel mixture layer around the electrodes. To do). Further, in a uniform combustion region where vaporization and atomization promotion of fuel spray is required, it is preferable to perform fuel injection in the first half of the valve opening (when the fuel injection amount is insufficient, the fuel is injected in the latter half of the valve opening. ). In the case of FIG. 19, even if there is a manufacturing error of the fuel injection valve 18, in order to prevent reliable interference between the intake valve 12 and the fuel spray, when fuel is injected in the first half of the valve opening, the time indicated by c11 The fuel injection is preferably terminated at a sufficiently early timing. When fuel injection is performed at the later stage of the valve opening, the fuel injection is started at a timing sufficiently later than the time indicated by c12.

  FIG. 20 shows still another embodiment of the present invention, which is a case where the intake air is closed late in order to reduce the pumping loss. Note that, in the present embodiment, as in the case of FIG. 18, the fuel injection mode is common to all cylinders, not the fuel injection mode for a part of the specific cylinders. In the present embodiment, the valve opening characteristic of the intake valve 12 corresponds to the basic characteristic of FIG. 18 that is phase-shifted by a predetermined amount to the slow side, and therefore the lift amount is the same as that of the basic characteristic. In the present embodiment, the valve opening timing is delayed by a predetermined amount considerably larger than the intake top dead center, and the valve closing timing is delayed by a predetermined amount considerably larger than the intake bottom dead center. The first half of the year. As in the case of FIG. 18, such a region where the intake air is slowly closed is a high load region in the stratified combustion region shown in FIG. 5 or a low load region in the uniform combustion region (when a transition region is set). May be a transition region). In the present embodiment, the region between c21 and c22 and the region between c23 and c24 is a region where the intake valve 12 and fuel spray interfere. The fuel injection timing is at least one of the two periods of the middle of the valve opening and the compression stroke (the first half of the compression stroke). In the stratified combustion region, it is preferable to inject fuel during the compression stroke (when the fuel injection amount is insufficient, the fuel is injected in the middle of the valve opening). In the uniform combustion region, it is preferable to perform fuel injection in the middle of the valve opening (when the fuel injection amount is insufficient, the shortage is injected in the compression stroke). In the first half of the valve opening, the fuel injection is not performed in response to a request that comes from the setting of the region where the intake air intake is closed. However, it is possible to perform the fuel injection in the first half of the valve opening. Further, in the fuel injection in the middle of the valve opening, in order to surely prevent interference due to manufacturing errors of the fuel injection valve 18, the fuel injection start timing is set to a timing sufficiently later than the time point c22, and the fuel injection ends. The timing is sufficiently earlier than the time c23.

  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. For one cylinder, the number of intake ports (switching valves) may be 1 or 3 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 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. When the fuel injection timing for the specific cylinder is changed, the fuel injection timing for all the other cylinders may be changed to the fuel injection timing changed for the specific cylinder. For specific cylinders that cause interference, gradually reduce the fuel injection amount in the middle of the opening of the intake valve, that is, gradually delay the injection start timing and gradually advance the injection end timing so that interference does not occur. You may make it perform the fuel injection in the middle of valve opening. 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 and a uniform combustion area. 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 circuit example which detects an ionic current. The figure which shows the relationship between an ionic current and an air fuel ratio. The figure which shows the circuit example which detects the insulation resistance of a spark plug electrode. The figure which shows the basic valve opening characteristic and fuel injection timing of an intake valve. The figure which shows the fuel-injection time when it is set as intake early closing. The figure which shows the fuel-injection time when it is set as intake late delay.

Explanation of symbols

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 42: Ion current detection circuit (Interference detection means)
43: Insulation resistance detection circuit (interference detection means)
50: Controller (basic injection timing setting means, injection timing changing 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 (10)

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,
In the spark ignition direct injection engine set to have at least a left-side nozzle directed to the left side of the electrode and a right-side nozzle directed to the right side of the electrode as the plurality of nozzles,
Basic injection timing setting means for setting, as a basic injection timing, a valve opening middle period in which the intake valve is in a high lift state in an intake stroke injection region in which fuel injection is performed in the intake stroke;
Interference detecting means for detecting interference between the fuel spray from the left and right nozzles and the intake valve when fuel injection is performed at the basic injection timing;
In the intake stroke injection region, the fuel injection timing for the specific cylinder in which the interference is detected by the interference detection means is limited so that the fuel injection at the basic injection timing does not cause the interference. Injection timing changing means for performing fuel injection during at least one of the first and second valve opening periods in a low lift state;
A spark ignition type direct injection engine characterized by comprising: In claim 1,
A spark ignition type characterized in that the restriction of fuel injection at the basic injection timing by the injection timing changing means is performed by allowing fuel injection to be performed only during a narrow period when the intake valve is in a higher lift state. Direct injection engine. In claim 1,
The spark ignition type direct current is characterized in that the fuel injection restriction at the basic injection timing by the injection timing changing means is performed by prohibiting fuel injection in the middle of the valve opening when the intake valve is in a high lift state. Jet engine. In any one of Claims 1 thru | or 3,
The fuel injection after the change by the injection timing changing means is at least two of the three periods of the valve opening middle period when the intake valve is in the high lift state and the valve opening early period and the valve opening late period when the intake valve is in the low lift state. A spark ignition direct injection engine characterized by being divided injection executed in a period. In claim 1,
Split injection of post-stage injection in which fuel injection is performed during the compression stroke and pre-stage injection in which fuel injection is performed during the intake stroke in a high load range where stratified combustion is performed so that the local air-fuel ratio around the electrode becomes rich Is set to do
The pre-stage injection in the specific cylinder is performed in at least one period of a middle period when the intake valve is in a high lift state or a late stage when the intake valve is in a low lift state.
This is a spark ignition direct injection engine. In claim 1,
Depending on the operating state of the engine, a stratified combustion region in which fuel injection is performed at least in the compression stroke so that the local air-fuel ratio around the electrode becomes rich, and a higher load and higher rotation than the stratified combustion region in the intake stroke Three regions are set: a uniform combustion region in which only fuel injection is performed, and a transition region in which fuel injection is performed in the compression stroke and the intake stroke as a boundary region between the stratified combustion region and the uniform combustion region,
In the transition region, the fuel injection in the intake stroke for the specific cylinder is at least one period of three periods of a middle period of opening of the intake valve when the intake valve is in a high lift state, a first period of opening of the valve during a low lift state, and a late period of opening the valve. Done in
This is a spark ignition direct injection engine. In claim 1,
In a uniform combustion region in which fuel injection is performed only in the intake stroke and the in-cylinder air-fuel ratio is rich (λ ≦ 1) below the stoichiometric air-fuel ratio, fuel injection for the specific cylinder is performed in a high lift state of the intake valve A spark-ignition direct injection engine, characterized in that it is divided injection that is performed in at least two periods among three periods of a middle valve opening period, a low valve lift first period valve opening period, and a second valve opening period. 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,
In the spark ignition direct injection engine set to have at least a left-side nozzle directed to the left side of the electrode and a right-side nozzle directed to the right side of the electrode as the plurality of nozzles,
Stratified combustion in which fuel injection is performed at least in the intake stroke so that the local air-fuel ratio around the electrode is rich in a high-load region in which fuel injection is performed in at least the compression stroke or in-cylinder air-fuel ratio is uniform. In the low load range in the region, the intake valve close timing is set to a predetermined crank angle before the intake bottom dead center so that the effective compression ratio becomes small,
Fuel injection is performed in at least one of the two periods of the first and second valve opening periods when the intake valve is in a low lift state.
This is a spark ignition direct injection engine. 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,
In the spark ignition direct injection engine set to have at least a left-side nozzle directed to the left side of the electrode and a right-side nozzle directed to the right side of the electrode as the plurality of nozzles,
Stratified combustion in which fuel injection is performed at least in the intake stroke so that the in-cylinder air-fuel ratio is uniform, and a high load region in the stratified combustion region in which fuel injection is performed at least in the compression stroke so that the local air-fuel ratio around the electrode becomes rich In the low load region in the region, the intake valve closing timing is determined to be after the predetermined crank angle from the intake bottom dead center so that the effective compression ratio becomes small,
Fuel injection is performed in at least one of the two periods of the valve opening middle period in which the intake valve is in a high lift state and the compression stroke.
This is a spark ignition direct injection engine. In any one of Claims 1 thru | or 9,
As a nozzle directed to the vicinity of the electrode, it has a lower nozzle directed to the extension near the tip of the electrode,
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,
This is a spark ignition direct injection engine.

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