JP2007177742A - Spark-ignition direct-injection engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce smoke and NOx while ensuring output in a high load region in a stratified combustion region. <P>SOLUTION: A first nozzle hole (a specific nozzle hole and its axis indicated by a sign L1) is directed to a lower part near an electrode E of an ignition plug 16 projected into a combustion chamber 6. For instance, the magnitude of an ion current changed according to a local air-fuel ratio around the electrode is detected to grasp a distance X (X1-X4) between the electrode E and the axis L1 of the specific nozzle hole for every cylinder. In the high load region in the stratified combustion region, fuel injection timing set to a compression stroke is advanced as to the cylinder shortest in the distance X and delayed as to the cylinder longest in the distance X. <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.

  2. Description of the Related Art Conventionally, there has been known a spark ignition type direct injection engine that includes an ignition plug and a fuel injection valve (injector) that directly supplies fuel into a combustion chamber so as to improve fuel efficiency by performing stratified combustion. When the injection port of the fuel injection valve is directed directly to the electrode for stratified combustion, there is a problem that the fuel tends to adhere to the electrode as droplets and the ignitability deteriorates. For this reason, as shown in Patent Document 1 below, 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 these injection holes are located below the electrodes near the ignition plug. The lower nozzle (specific nozzle) directed to the left, the left nozzle directed to the left near the electrode, and the right nozzle directed to the right near the electrode are concentrated in the vicinity of the electrode by fuel spray from these three nozzles. An arrangement for obtaining a stratification to form a mixture layer 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. .
JP 2005-98119 A JP 2005-273554 A Japanese Patent Laying-Open No. 2005-256791

  For stratified combustion, when the injection port of the fuel injection valve is directed to the vicinity of the electrode, fuel spray from the lower injection port directed downward in the vicinity of the electrode (extension direction of the electrode tip) is most important. The fuel spray from the lower injection port (specific injection port) is greatly displaced in the vertical direction (cylinder axis direction) from the electrode in order to form an appropriate rich mixture layer around the electrode and fuel. This is important in preventing the spray from directly contacting the electrode.

  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. In addition, for spark plugs, the amount of protrusion into the combustion chamber differs depending on the manufacturing error, and the amount of protrusion of the electrode into the combustion chamber is particularly difficult because it is difficult to finish the insulator part with high accuracy. A certain amount of error (for example, ± 0.7 mm) is unavoidable.

  As described above, due to manufacturing errors of both the spark plug and the fuel injection valve, a considerable difference is caused in the distance between the electrode tip and the specific nozzle (lower nozzle) between the cylinders. In particular, in cylinders close to the above distance, the fuel spray from the specific nozzle tends to be rich around the electrode, and particularly smoldering tends to occur in the high load region in the stratified combustion region, which is a major cause of smoke and NOx generation. It becomes. In order to reduce this smoke and NOx, it is conceivable to reduce the fuel injection amount, but since it is a high load region, it is strongly required to secure the output, and it is a fact that the fuel injection amount is reduced. It becomes difficult.

  The present invention has been made in consideration of the above-described circumstances, and its object is to provide a spark ignition type direct current generator capable of reducing smoke and NOx while ensuring output in a high load region in a stratified combustion region. To provide an 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,
Each cylinder is provided with a spark plug with an electrode protruding into the combustion chamber and a multi-hole type fuel injection valve having a plurality of injection holes for direct fuel injection into the combustion chamber,
In each cylinder, the axis of some of the plurality of nozzle holes is directed to pass near the tip of the electrode and the extension line thereof,
In a spark ignition direct injection engine in which fuel injection is performed at least in the latter half of the compression stroke to perform stratified combustion in a predetermined operation region that is a low rotation / low load region,
For each cylinder, distance data grasping means for grasping distance data which is a value related to the distance between the electrode and the fuel spray from the specific nozzle,
Injection timing for relatively advancing the fuel injection timing of the cylinder whose distance grasped by the distance data grasping means is relatively small in the high load region in the predetermined operation region as compared with other cylinders Correction means;
It is supposed to be equipped with. According to the above solution, the distance between the electrode and the fuel spray from the specific nozzle is small, which means that the area around the electrode is relatively rich as compared with the case where the distance is large, and smoke and NOx generation is large. Cause. However, since the fuel injection timing of the cylinder having the smaller distance is advanced, the spread angle of the fuel spray at the ignition timing is larger than when the angle is not advanced, and the air-fuel ratio around the electrode becomes lean. As a result, smoke and NOx are reduced. Of course, since it is not necessary to reduce the fuel injection amount itself, there is no problem in securing the output. In addition, since it is a high load region in the stratified combustion region, the stratified robustness is high (good-wide) compared to the low load region, that is, the fuel injection timing and ignition timing within the range that can ensure combustion stability. Since the allowance for change is large, there is no particular problem in terms of ensuring combustion stability even if the fuel injection timing is advanced.

A preferred mode based on the first solution is as set forth in claims 2 to 7 in the claims. That is,
Fuel injection in the first half of the compression stroke of the cylinder in which the distance is relatively small in the high load range in the predetermined operation range, so that the fuel injection is performed not only in the second half of the compression stroke but also in the first half of the compression stroke. The timing is advanced relative to the other cylinders (corresponding to claim 2). In this case, by advancing the fuel injection timing in the first half of the compression stroke that does not significantly affect stratification, it is preferable to obtain the effect corresponding to claim 1 while ensuring stratification reliably. .

  In the high load region in the predetermined operation region, the fuel injection timing in the latter half of the compression process is set to be substantially the same between the cylinders (corresponding to claim 3). In this case, the fuel injection timing in the latter half of the compression stroke, which has a great influence on stratification, is set to be substantially the same between the cylinders, which is preferable for ensuring stratification reliably in each cylinder.

  In the low load region in the predetermined operation region, the fuel injection timing and the ignition timing are set to be substantially the same between the cylinders, and the air-fuel ratio of the cylinder having the large distance is richly corrected, and the distance is The air-fuel ratio of the smaller cylinder is lean-corrected (corresponding to claim 4). In this case, in the low load region where the stratification robustness with a small allowance for changing the fuel injection timing and the ignition timing is low, the overall increase in the fuel injection amount is prevented or suppressed, and each cylinder is controlled by the air-fuel ratio correction control. Combustion stability can be ensured.

  The injection timing correction means is configured to retard the fuel injection timing of the cylinder having the relatively large distance relative to the other cylinders in a high load range in the predetermined operation range. (Corresponding to claim 5). In this case, it is preferable to make the combustion state in each cylinder as uniform as possible, that is, to make the output (combustion torque), discharged smoke and NOx as uniform as possible among the cylinders. In addition, since the periphery of the electrode of the cylinder with a large distance is relatively lean, it is corrected to rich by delaying the fuel injection timing, thereby improving ignitability and consequently improving combustion stability. However, it is preferable.

The distance data grasping means includes a current detecting means for detecting an ion current flowing through the electrode, and is configured to determine the distance based on the magnitude of the detected ion current. (Corresponding to claim 6).
The distance data grasping means includes a resistance detecting means for detecting an insulation resistance of the electrode, and is configured to determine the distance based on the detected insulation resistance ( Claim 7).
In the case of claims 6 and 7, a specific method for grasping the distance is provided.

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, there are provided a spark plug with an electrode protruding into the combustion chamber and a multi-hole type fuel injection valve having a plurality of injection holes arranged at the periphery of the combustion chamber and directly injecting fuel into the combustion chamber,
In each cylinder, the axis of some of the plurality of nozzle holes is directed to pass near the tip of the electrode and the extension line thereof,
In a spark ignition direct injection engine in which fuel injection is performed at least in the latter half of the compression stroke to perform stratified combustion in a predetermined operation region that is a low rotation / low load region,
Effective pressure grasping means for grasping a value related to the indicated mean effective pressure for each cylinder;
The fuel injection timing of the cylinder in which the indicated mean effective pressure grasped by the effective pressure grasping means is relatively small in the high load region in the predetermined operation region is relatively advanced compared to the other cylinders. Injection timing correction means for
It is supposed to be equipped with. According to the above solution, the smaller the indicated mean effective pressure, the greater the smoke and NOx emissions. By advancing the fuel injection timing of the cylinder where the indicated mean effective pressure is reduced, the claim 1 The same effect can be obtained. In particular, since the fuel injection timing is corrected by directly grasping the combustion mode, such as the value related to the indicated mean effective pressure, it is preferable for sufficiently obtaining the effect corresponding to the first aspect.

A preferred mode based on the second solution is as described in claim 9 in the claims. That is,
The effective pressure grasping means includes an angular speed detecting means for detecting an engine angular speed immediately after the explosion process for each cylinder, and is set so as to determine the indicated mean effective pressure based on the detected angular speed. Yes (corresponding to claim 9). In this case, it is possible to detect (estimate) the indicated mean effective pressure by a conventionally commonly used method of angular velocity detection.

A preferred mode based on the first and second solutions is as described in claim 10 and subsequent claims. That is,
The electrode is disposed substantially in the center of the combustion chamber;
The fuel injection valve is disposed at a peripheral portion of the combustion chamber and has, as the plurality of injection holes, other injection holes directed in the piston top surface direction in addition to the specific injection holes,
There are two intake valves for each cylinder,
The fuel injection valve is positioned between the two intake valves;
(Corresponding to claim 10). In this case, so-called side injection is provided in which the fuel injection valve is provided at the peripheral edge of the combustion chamber. Since some of the nozzle holes are directed to the top surface of the piston, in addition to the stratified combustion that enriches the surroundings of the electrodes exclusively, the injection can also be applied to the case of performing uniform combustion with the fuel distributed evenly in the cylinder as much as possible. An aspect can be obtained. In addition, the present invention is preferable when the present invention is applied to an intake two-valve engine that is widely used especially for automobiles, and the fuel injection valve is effectively used in a large space between the two intake valves. Can be arranged.

As the nozzle directed to the vicinity of the electrode, in addition to the specific nozzle, a left nozzle directed to the left side of the electrode, and a right nozzle directed to the right side of the electrode,
The distance from each nozzle of the specific nozzle, left side nozzle and right side nozzle is set to 20 mm or more,
The opening angle formed by the specific nozzle and the left nozzle is set in a range of 15 to 25 degrees, and the fuel spray from the specific nozzle and the fuel spray in a predetermined operation region that is a low rotation / low load region of the engine The fuel spray from the left side nozzle is set to be continuous with each other by the mutual interference effect,
The opening angle formed by the specific nozzle and the right nozzle is set in a range of 15 to 25 degrees, and the fuel spray from the specific 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 11). 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, smoke and NOx can be reduced while securing an output.

  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 setting of the axial position of a specific nozzle according to the amount of electrode protrusion into the combustion chamber (of the fuel injection valve) Selection) and detailed fuel injection control according to the engine load in the stratified combustion region 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. Although not shown, the exhaust passage 31 is provided with a linear oxygen sensor, a three-way catalyst, and a NOx absorbent in order from the upstream side to the downstream side. The linear oxygen sensor is used to detect the air-fuel ratio based on the oxygen concentration in the exhaust gas, and a linear output with respect to the oxygen concentration can be obtained within a predetermined range including the theoretical air-fuel ratio. ing. The NOx absorbent absorbs NOx in an atmosphere with a high oxygen concentration in the exhaust, while releasing NOx absorbed as the oxygen concentration decreases, and reduces and purifies the released NOx by HC, CO, etc. in the exhaust. NOx absorption reduction type.

  At the upper part of the combustion chamber 6, an ignition plug 16 is disposed 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) (FIG. 2). See also). 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.

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 is a lower nozzle hole or a specific 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.

  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.

  Next, the point of axial position setting (selection of the fuel injection valve) of the specific nozzle according to the amount of electrode protrusion into the combustion chamber will be described with reference to FIGS. First, FIG. 14 shows an example in which the spark plug 16 is actually attached to the cylinder head 4 and the amount of protrusion of the electrode E from the combustion chamber 6 (the upper surface thereof) is measured. In addition, as a spark plug to be used, the length from the seating surface to the cylinder head mounting hole (the locking step surface provided on the inner surface of the spark plug 16) to the tip of the insulator covering the center electrode is determined by a preliminary inspection. For example, an error of ± 0.7 mm or less is used. By setting such an error range, particularly in an atmospheric pressure state (corresponding to a pressure state in the cylinder in the intake stroke and the first half of the compression stroke), the fuel spray from the specific nozzle is not in direct contact with the electrode E. And it is set as the aspect which is not separated from the electrode E too much. The cylinder head 4 is placed on the base K with the ignition plug 16 attached to each cylinder (four cylinders in the embodiment) with the mating surface 4g side on the cylinder block side facing upward. . In this state, for example, the distance from the mating surface 4g of the tip (upper end in FIG. 14) of each electrode E is measured by the laser measuring instrument LS. This measurement result is stored in a storage means (memory) MR built in the controller 50. The cylinder head 4 is finished with extremely high accuracy including its combustion chamber shape and the like, and the manufacturing error of the cylinder head 4 itself is smaller than the manufacturing error of the spark plug 16 and the fuel injection valve 18 (the nozzle thereof). It can be ignored. Note that LS1 is a light emitting unit of the laser measuring instrument LS, and LS2 is a light receiving unit of the laser measuring instrument LS.

  Measurement data obtained by the method shown in FIG. 14 is, for example, as shown in FIG. Since the data obtained by the laser measuring instrument LS is the distance formed by the mating surface 4g and the tip of the electrode E, the projection Y from the combustion chamber at the tip of the electrode E increases as the distance decreases. In FIG. 15, the number 3 (NO3) cylinder, the number 1 (NO1) cylinder, the number 2 (NO2) cylinder, the number 4 (NO4) cylinder in order from the largest to the smallest amount of protrusion of the electrode E tip from the combustion chamber. It has become.

  FIG. 16 shows an angle θ formed between the axis LB of the fuel injection valve 18 and the axis L1 of the specific nozzle (first nozzle), and an error from a predetermined value of θ is ± 3. The fuel injection valve 18 set to 5 degrees or less is used. The total θ of four fuel injection valves 18 corresponding to four cylinders is measured, and the data is attached to each fuel injection valve 18 by an IC tag or the like. The actual measurement values are θ1, θ2, θ3, and θ4 in order from the smallest to the largest. As is clear from FIG. 16 in particular, the axis L1 of the specific nozzle becomes closer to the electrode E as θ is larger.

  The amount of protrusion E of the electrode E measured into the combustion chamber Y (measured data is Y1 to Y4) and the angle θ (measured data is θ1 to θ4) measured as described above are collated to determine the combination. In other words, the spark plug 16 having the largest Y1 data value is associated with the fuel injection valve 18 having the smallest angle θ1, and the ignition value having the second Y2 data value is the second largest. The fuel injector 18 having the second smallest angle θ2 is associated with the plug 16, and the third smallest angle with respect to the spark plug 16 having the data value Y3 with the third largest protrusion amount. The fuel injection valve 18 having θ3 is associated with the spark plug 16 having the data value of Y4 having the smallest protrusion amount, and the fuel injection valve 18 having the largest angle θ4 is associated with it. Then, the fuel injection valve 18 is selectively assembled to the cylinder head 4 so as to have the relationship thus associated. The assembled state is shown in FIG. In addition, in the atmospheric pressure state, the fuel spray from the specific nozzle is prevented from interfering with the electrode, but the diameter of the fuel spray from the specific nozzle is about 2 mm in the vicinity of the electrode E.

  After the assembly shown in FIG. 17, the distance X between the electrode E and the axis L1 of the specific nozzle in each cylinder is indicated by X1 to X4 in order from the largest to the smallest, and these X1 to X4 are Y1 to Y4. Calculation is performed based on θ1 to θ4 (for example, X1 is referred to based on Y1 and θ1). Thus, in the embodiment, the cylinder having the largest distance X1 is the third cylinder, the cylinder having the second largest distance X2 is the fourth cylinder, and the cylinder having the third largest distance X3. Is the second cylinder, and the cylinder having the smallest distance X4 is the first cylinder. The storage means MR stores the relationship between the distance X (X1 to X4) and the corresponding cylinder, but at least the cylinder having the largest distance X1 (the third cylinder) and the smallest. The cylinder having the distance X4 (first cylinder) is stored.

  FIG. 18 collectively shows a procedure for assembling the spark plug 16 and the fuel injection valve 18 in association with each other. That is, in step Q1, the spark plug 16 is attached to the cylinder head 4 to be used as it is for an actual machine, and then in step Q2, as shown in FIG. 14, the amount of projection of the electrode E from the combustion chamber in each spark plug 16 is set. Measurement is performed, and the measurement results (Y1 to Y4) are stored in the storage means MR. After step Q2, in step Q3, the cylinder head 4 to which the spark plug 16 is attached is assembled to the cylinder block, and normal engine assembly is performed (an assembly of the crankshaft and the like is also performed).

  In parallel with the above steps Q1 to Q3, in step Q5, the angle θ between the axis LB and the axis L1 of the specific nozzle is measured for the fuel injection valves 18 for all cylinders (measured values of θ1 to θ4 are obtained). ). The measured value obtained in this step Q5 is attached to each fuel injector 18 as data specific to each fuel injector 18 using a tag or the like. In the embodiment, the measurement data θ (processing in step Q5) is obtained at a place different from the engine assembly factory, more specifically at the factory that manufactures the fuel injection valve 18, and the engine assembly A fuel injection valve 18 to which measurement data θ is attached in advance is delivered to the factory.

  In step Q4, the fuel injection valve 18 is attached to the cylinder head 4 which is assembled to the cylinder block or the like and the spark plug 16 is already attached. When the fuel injection valve 18 is attached, the angle θ (θ1 to θ4) is associated with the amount of protrusion Y (Y1 to Y4) of the electrode E from the combustion chamber.

  In addition, between each step Q2 and step Q3, all the spark plugs 16 may be removed from the cylinder head 4, and each spark plug 16 may be attached to the cylinder head 4 again in step Q4. In this case, the assembly of the cylinder head 4 to the cylinder block or the like can be performed in the state where the spark plug 16 is not attached as in the conventional case. Further, the spark plug 16 and the fuel injection valve 18 are associated with each other based on the measurement data obtained in step Q2 and the data obtained in step Q5 (for example, one spark plug 16 and one fuel plug). The set body for one cylinder including the injection valve 18 is divided into four sets for all cylinders). In step Q4, the spark plug 16 and the fuel injection valve 18 that are in a set relationship for each cylinder are connected. It can also be installed.

  FIG. 19 shows a modification of FIG. In the present embodiment, in step Q11 corresponding to step Q1 in FIG. 18, the cylinder head used is not for an actual machine actually used for engine assembly, but for a dummy that is not used for engine assembly (for measurement). As this dummy cylinder head, a dedicated product for measurement may be prepared separately, but in the embodiment, the actual product is used as it is. In step Q12, the projection amount Y (Y1 to Y4) of each spark plug 16 from the combustion chamber is measured, and then in step Q13, each spark plug 16 is removed from the dummy cylinder head. In Q14, the cylinder head (for actual machine) is assembled to the cylinder block or the like. This step Q14 corresponds to step Q3 in FIG. 18, but is a state in which the ignition plug 16 is not attached to the cylinder head 4. In parallel with the above steps Q11 to Q14, in step Q16 (corresponding to step Q5), the angle θ (θ1 to θ4) of each fuel injection valve 18 is measured. Finally, in step Q15, a combination of the spark plug 16 and the fuel injection valve 18 is selected so that the protrusion amount Y and the angle θ are associated with each other, and the spark plug is in the state of the selected combination. 16 and the fuel injection valve 18 are attached to the cylinder head.

  20 and 21 show the amount Y of projection of the spark plug 16 from the combustion chamber (data) without actually attaching the spark plug 16 to the cylinder head 4. In detail, in FIG. 20, in the structure near the tip of the spark plug 16, the center electrode E1 of the electrode E is surrounded by the insulator 16a, and the center electrode E1 has only the tip. It is slightly exposed from the insulator 16a, and the peripheral electrode E2 surrounds the exposed center electrode E1. The spark plug 16 has a seating surface 16b that comes into contact with a locking surface formed in the mounting hole (inner circumferential surface) of the cylinder head 4, and for example, the front end of the insulator 16a with the seating surface 16b as a reference position. A length (distance) Z to the surface is measured for each spark plug 16. The length of the center electrode E1 protruding from the tip end surface of the insulator 16a is controlled to be constant, but the length Z has a considerable error (for example, ± 0.7 mm). The error of the length Z becomes a very large factor giving an error to the protruding amount Y of the electrode E from the combustion chamber. Therefore, by measuring the length Z, the protrusion amount Y of the electrode E from the combustion chamber is estimated. Note that the larger the length Z, the larger the protrusion amount Y.

  In FIG. 21, in step Q21, the length Z is measured for the spark plugs 16 for all cylinders (in the embodiment, there are four spark plugs because there are four cylinders), and data Z1 to Z4 are obtained. Then, among Z1 to Z4, the maximum value is classified as Zmax, the minimum value as Zmin, and the intermediate value (there are two) as Zx. Thereafter, in Q22, normal engine assembly for assembling the cylinder head 4 to the cylinder block or the like is performed (corresponding to Q14 in FIG. 19).

  On the other hand, in parallel with steps Q21 and Q22, in step Q24, the angle θ (θ1 to θ4) of each fuel injection valve 18 for all cylinders (four cylinders in the embodiment) is measured. Then, among θ1 to θ4, the maximum value is classified as θmax, the minimum value is classified as θmin, and the intermediate values (there are two) are classified as θx.

  In step Q23, the θmax fuel injector 18 is associated with the Zmax spark plug 16, the θmax fuel injector 18 is associated with the Zmin spark plug 16, and the θx fuel plug 18 is associated with the Zx spark plug 16. The fuel injectors 18 are associated (Zx and θx are associated with two groups). Then, the spark plug 16 and the fuel injection valve 18 are assembled to the cylinder head 4 in this associated state. According to the embodiment of FIG. 21, not only the fuel injection valve 18 but also the spark plug 16 is measured for the protrusion amount Y (a value related thereto) without being assembled to the cylinder head 4 or the like, The association between the spark plug 16 and the fuel injection valve 18 can be performed in a completely separate process from the engine assembly process. In step Q23, the assembly operator supplies the ignition plug 16 and the fuel injection valve 18 and the fuel injection valve 18 as a set of two pieces to the assembly process, so that the installation operator can install the ignition plug 16 and the fuel injection valve during the assembly. The attachment work can be performed without being conscious of the association with 18.

  22 to 24 show another embodiment of the present invention, and show a case where the fuel injection valve 18B is provided substantially in the center of the combustion chamber (in the case of center injection). That is, the ignition plug 16 is disposed in a substantially inclined state with respect to the cylinder axis at a substantially central portion of the combustion chamber, and the fuel injection valve 18B is disposed substantially along the cylinder axis. As shown in FIG. 24, the fuel injection valve 18B has a plurality (six in the embodiment) of nozzle holes 61a to 61f at equal intervals in the circumferential direction. The axis of each nozzle hole 61a to 61f is set to have the same angle with respect to the axis of the fuel injection valve 18B, and the fuel spray from each nozzle hole 61a to 61f is directed toward the piston top surface. Yes. And one specific nozzle 61a is set so that it may go to the piston top surface after passing below the vicinity of the electrode E. In the present embodiment, the larger the protrusion amount of the electrode E of the spark plug 16 into the combustion chamber, the larger the fuel injection valve 18B that corresponds to the smaller angle θ between the axis LB of the fuel injection valve 18B and the axis L1 of the specific injection port 61a. Attached.

  25 and 26 show another method for detecting the distance X between the electrode E and the axis of the specific nozzle, and the distance depends on the magnitude of the ionic current flowing through the electrodes (center electrode E1 and peripheral electrode E2). A method for discriminating X is shown. First, as is known, the peripheral electrode E2 of the spark plug 16 is grounded via the engine 1, and the center electrode E1 is connected to the ignition circuit 17. 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, an ion current flows between the center electrode E1 and the peripheral electrode E2 due to the fuel spray existing around the electrode immediately before ignition, and a voltage corresponding to the magnitude of the ion current is generated by the voltmeter 42e. It is detected (the larger the detection voltage, the larger the ionic current). The ionic current changes as shown in FIG. 26 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). The rich air-fuel ratio means that the distance X between the electrode E and the axis of the specific nozzle is small. In this way, the ion current (that is, the distance X) is detected and stored for each cylinder (at least the cylinder with the maximum distance X and the cylinder with the minimum distance are 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).

  27 uses a resistance detection circuit 43 instead 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 E1 and the peripheral electrode E2, but this insulation resistance decreases as the air-fuel ratio of the air-fuel mixture around the electrode becomes richer. Note that the greater the current detected by the ammeter 43a, the smaller the insulation resistance and the shorter the distance between the electrode E and the fuel spray.

Next, details such as fuel injection control in the stratified charge combustion zone will be described.
(1) Idle region In the idle region, the stratification robustness is poor, and the change range of the ignition timing and the fuel injection timing within a range in which the combustion stability can be ensured is small. Further, when focusing on each cylinder, the combustion stability is relatively poor for a cylinder with a large distance X where the periphery of the electrode is relatively rich, and the combustion stability is relatively good for a cylinder with a small distance X It becomes. Therefore, in the idle region, correction for enriching the air-fuel ratio is performed for the cylinder having the maximum distance X (the third cylinder in the example of FIG. 17) to ensure combustion stability. At this time, a correction is made so that the air-fuel ratio of the cylinder having the minimum distance X with sufficient margin for combustion stability (the first cylinder in the example of FIG. 17) is made lean (for the cylinder having the intermediate distance X). Is no correction of air-fuel ratio). In the idling range, the air-fuel ratio is feedback-controlled so that the actual engine speed becomes the target idling speed (for example, 550 rpm), but the above-mentioned rich correction and lean correction correct this feedback correction value. By doing that. For example, when the engine speed is equal to or lower than a predetermined speed and the accelerator opening is 0, it is determined that the engine is in the idling range.

(2) Low load region other than the idling region Even in the low load region in the stratified combustion region, the region other than the idling region has a margin for combustion stability as compared with the idling region. When in this region, air-fuel ratio feedback control is performed so that the actual air-fuel ratio detected by the air-fuel ratio sensor S6 becomes the target air-fuel ratio (the target air-fuel ratio is leaner than the stoichiometric air-fuel ratio). At this time, the feedback correction value is lean-corrected for the cylinder with the shortest distance X, and the feedback correction value is rich-corrected for the cylinder with the maximum distance X. Note that the actual air-fuel ratio is an average value of several detection values detected by the air-fuel ratio sensor S6 (the number of times at least exhaust gas for all cylinders can be detected).
(3) High load range Air-fuel ratio feedback control is performed so that the air-fuel ratio detected by the air-fuel ratio sensor S6 becomes the target air-fuel ratio (the target air-fuel ratio is leaner than the stoichiometric air-fuel ratio). Further, the fuel injection timing of the cylinder having the minimum distance X is advanced, and the fuel injection timing of the cylinder having the maximum distance X is retarded. The fuel injection is divided injection in the latter half and the first half of the compression stroke, but the fuel injection timing in the second half of the compression stroke is substantially the same among the cylinders (in the embodiment, it is completely the same), and the fuel injection in the first half of the compression stroke is performed. The time is changed according to the distance X as described above. Note that the ignition timing is substantially the same between the cylinders (completely the same in the embodiment). Note that the fuel injection timing is not corrected for the cylinder having the intermediate distance X, but the advance angle correction threshold value and the retard angle correction threshold value are set for the distance X. It may be determined whether to advance or retard at the threshold, and the advance amount or retard amount is changed according to the degree of deviation from the threshold value of the distance X. May be. It should be noted that the advance angle correction amount or the retard angle correction amount of the fuel injection timing in the first half of the compression stroke can be, for example, a correction amount corresponding to 10 deg to 20 deg from the set state of FIG.
(4) Medium Load Range Air-fuel ratio feedback control is performed so that the air-fuel ratio detected by the air-fuel ratio sensor S6 becomes the target air-fuel ratio (the target air-fuel ratio is leaner than the theoretical air-fuel ratio). The fuel injection timing and the ignition timing are not different among the cylinders, and are basically controlled (normal control).

  A control example (control example by the controller 50) of the fuel injection control in the low load region in the stratified combustion region described above will be described with reference to the flowchart shown in FIG. In the following description, R represents a step. First, in R31, after data such as the engine speed is input, in R32, it is determined whether or not the current operating state is a stratified combustion region by referring to the map shown in FIG. When the determination in R32 is YES, it is determined in R33 whether or not the low load range shown in FIG. If the determination in R33 is YES, it is determined in R34 whether or not the vehicle is in the idle range.

  If the determination in R34 is YES, the air-fuel ratio is feedback-controlled in R35 so that the actual engine speed becomes the target idle speed. A feedback correction value (basic value) obtained by feedback control is set to ΔFB. Next, in R36, the feedback correction value for the cylinder having the maximum distance X (the third cylinder in the example of FIG. 17) is the richening correction value with respect to the feedback correction value ΔFB obtained in R35. Δf (Δf> 0) is added to obtain a final feedback correction value ΔF. The enrichment correction value Δf can be set to a certain value, but is preferably a value having a predetermined ratio (eg, 30%) of ΔFB, for example. Further, in order to suppress an increase in the fuel injection amount to all the cylinders, the feedback correction value of the cylinder having the minimum distance X (the first cylinder in the example of FIG. 17) is the feedback obtained by R35. The lean correction value Δf (Δf> 0) is subtracted from the correction value ΔFB to obtain the final feedback correction value ΔF. The correction amount for enrichment and the correction amount for leaning are set to the same value Δf. For the cylinder having the intermediate distance X (the second cylinder and the fourth cylinder in the example of FIG. 17), the feedback correction value ΔFB obtained in R35 is used as it is. In this way, the total feedback correction amount for all cylinders is not changed. It is possible to set the rich correction amount and the lean correction amount to be different, but in this case, the rich correction amount is larger than the lean correction amount. Setting to a value is preferable in terms of ensuring combustion stability, but from the viewpoint of fuel efficiency, it is preferable to make the correction amount for leaning larger than the correction amount for enrichment. .

  After R36, the fuel injection amount corrected in R36 is injected in the latter half of the compression stroke for each cylinder, and ignition is performed. After R37, in R38, the distance X is detected and stored using ion current detection or the like, as described above, in the steady operation state in the stratified combustion region.

  If the determination in R34 is NO, the feedback control correction value ΔFB is determined in R39 so that the actual air-fuel ratio becomes the target air-fuel ratio (corresponding to R35). Thereafter, in R40, the rich correction is performed by the feedback correction value Δf of the cylinder having the maximum distance X, and the feedback correction value of the cylinder having the minimum distance is corrected by leaning by the Δf (R36). Correspondence). Note that there is no change in the feedback correction value of the cylinder having the intermediate distance X. After R40, after obtaining R41 (corresponding to R37), the process proceeds to R38.

  When the determination in R33 is NO, it is determined in R42 whether or not it is a high load region in the stratified combustion region shown in FIG. When the determination of R42 is YES, in R43, the fuel injection timing of the cylinder having the minimum distance X is corrected and the fuel injection timing of the cylinder having the maximum distance X is retarded. It is corrected. It should be noted that the fuel injection timing is not corrected for the cylinder having the intermediate distance X. This change in the fuel injection timing is the fuel injection timing in the first half of the compression stroke, and the fuel injection timing in the second half of the compression stroke is the same for each cylinder. After this R43, after fuel injection is executed in R44 (corresponding to R37), the routine proceeds to R38.

  When the determination of R42 is NO, it becomes a medium load region in the stratified combustion region. At this time, normal (basic) control is performed without the air-fuel ratio and the fuel injection timing being different among the cylinders. If the determination in R32 is NO, the process returns as it is because it is not a stratified combustion area and is not directly related to the present invention.

  FIG. 29 shows still another embodiment of the present invention. For example, in the high load region in the stratified combustion region, the difference (variation) in angular velocity between the cylinders is taken into consideration instead of the distance X. That is, the fuel injection is controlled in consideration of the state corresponding to the indicated mean effective pressure in each cylinder. That is, when ignition is performed in a certain cylinder, the angular velocity gradually increases and then gradually decreases, and when ignition of the next cylinder is performed, the angular velocity gradually increases and then decreases. However, FIG. 29 shows how the angular velocity fluctuates in an overlapping manner. Note that the fluctuation range shown in FIG. 29 is a deviation between the maximum values of the angular velocities. In the cylinder where the angular velocity is large, the combustion torque is large, that is, the indicated mean effective pressure is large. Conversely, in the cylinder where the angular velocity is small, the combustion torque is small, that is, the indicated mean effective pressure is small. In other words, the smaller the indicated mean effective pressure is, the smaller the distance X between the electrode E and the axis of the specific nozzle, and the air-fuel ratio around the electrode is rich, and smoldering is likely to occur. It can be considered that the cylinder is likely to generate smoke and NOx.

  In the steady operation state in the stratified charge combustion zone, for each cylinder, the angular speed (change speed of the crank angle) is detected immediately after ignition, and the cylinder or the angular speed at which the angular speed (the maximum value) is minimized is preset. A cylinder smaller than the predetermined value is determined to be a cylinder having a small indicated mean effective pressure, and is stored in the storage means MR. For the cylinder determined to have a low indicated mean effective pressure, the fuel injection timing is advanced (corresponding to R43 in FIG. 28). In addition, as a method for detecting the value related to the indicated mean effective pressure, various conventionally proposed methods can be adopted as appropriate, but it is not necessary to provide a special sensor or the like separately based on the angular velocity. Therefore, it is preferable in terms of cost and implementation.

  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. The diameter and length of each nozzle hole may be set the same. 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. In the high load range in the stratified charge combustion zone, the advance angle correction amount of the fuel injection timing is gradually decreased from the cylinder with the smaller distance X (or the indicated mean effective pressure) to the larger cylinder, and the advance angle is corrected for a plurality of cylinders. In addition to this, the retardation correction amount for the plurality of cylinders is corrected so that the retardation correction amount of the fuel injection timing is gradually decreased from the larger distance X (or the indicated mean effective pressure) to the smaller one. You may make it do. Depending on the magnitude of the distance X, the correction amount of the advance angle or delay angle of the fuel injection timing may be changed. 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 second half of the compression stroke in the entire stratified combustion region (in this case, the advance correction or retard correction of the fuel injection timing is the same as the correction of the fuel injection timing in the second half of the compression stroke). Become). 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 simplified side view which shows an example which measures the amount of electrode protrusions into a combustion chamber. The figure which shows an example of the measurement result in FIG. The simplified side view which shows the condition which the change of the angle (theta) which the axis line of a specific nozzle hole and the axis line of a fuel injection valve give to the change of the distance of the axis line of a specific nozzle hole and an electrode. The figure which shows the positional relationship of the state which assembled | attached the amount of protrusion Y and the angle (theta) of the electrode into the combustion chamber, and the fuel spray from a specific nozzle at that time. The block diagram which shows the assembly | attachment process of an ignition plug and a fuel injection valve. The block diagram which shows the modification of FIG. The principal part figure for demonstrating that the data regarding the protrusion amount to the combustion chamber of an electrode is obtained in a spark plug independent state. The block diagram corresponding to FIG. 18, FIG. 19 which shows the assembly | attachment process to the engine of a spark plug and a fuel injection valve using the measured value obtained in FIG. The principal part perspective view which shows embodiment at the time of providing a fuel injection valve in the approximate center part of the combustion chamber. FIG. 23 is a simplified side cross-sectional view showing a relationship between an electrode and an injection direction of a fuel injection valve in the structure of FIG. The figure when FIG. 23 is seen from the lower side (piston top surface side). 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 flowchart which shows the example of control of this invention. The figure which shows the magnitude relationship of the angular velocity between cylinders.

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 flap 16a: Insulator 16b: Seating surface (reference position)
17: Ignition circuit 18: Fuel injection valve 18B: Fuel injection valve (FIGS. 22 to 24)
42: Ion current detection circuit 43. Insulation resistance detection circuit 61a: specific nozzle (FIG. 24)
E: Spark plug electrode E1: Center electrode E2: Peripheral electrode LB: Fuel injection valve axis L1: First injection port (specific injection port) axis A1: Spray angle of fuel injected from the first injection port (specific injection port) LS : Measuring instrument (measures the amount of electrode protrusion from the combustion chamber)
MR: Storage means (for storing detected values)
Y (Y1 to Y4): Projection amount of electrode into combustion chamber θ (θ1 to θ4): Angle X (X1 to X4) formed between the axis of the specific nozzle and the axis of the fuel injection valve: The axis of the electrode and the specific nozzle Distance S1: engine speed sensor S6: air-fuel ratio sensor (linear oxygen sensor)

Claims (11)

Each cylinder is provided with a spark plug with an electrode protruding into the combustion chamber and a multi-hole type fuel injection valve having a plurality of injection holes for direct fuel injection into the combustion chamber,
In each cylinder, the axis of some of the plurality of nozzle holes is directed to pass near the tip of the electrode and the extension line thereof,
In a spark ignition direct injection engine in which fuel injection is performed at least in the latter half of the compression stroke to perform stratified combustion in a predetermined operation region that is a low rotation / low load region,
For each cylinder, distance data grasping means for grasping distance data which is a value related to the distance between the electrode and the fuel spray from the specific nozzle,
Injection timing for relatively advancing the fuel injection timing of the cylinder whose distance grasped by the distance data grasping means is relatively small in the high load region in the predetermined operation region as compared with other cylinders Correction means;
A spark ignition type direct injection engine characterized by comprising: In claim 1,
Fuel injection in the first half of the compression stroke of the cylinder in which the distance is relatively small in the high load range in the predetermined operation range, so that the fuel injection is performed not only in the second half of the compression stroke but also in the first half of the compression stroke. A spark ignition direct injection engine characterized in that the timing is advanced relative to other cylinders. In claim 2,
A spark ignition direct injection engine characterized in that the fuel injection timing in the latter half of the compression process is set to be substantially the same between the cylinders in the high load range in the predetermined operation range. In claim 1,
In the low load region in the predetermined operation region, the fuel injection timing and the ignition timing are set to be substantially the same between the cylinders, and the air-fuel ratio of the cylinder having the large distance is richly corrected, and the distance is A spark-ignition direct injection engine characterized in that the air-fuel ratio of a small cylinder is lean-corrected. In claim 1,
The injection timing correction means is configured to retard the fuel injection timing of a cylinder having the relatively large distance in comparison with other cylinders in a high load range in the predetermined operation range. Features a spark ignition direct injection engine. In any one of Claims 1 thru | or 5,
The distance data grasping means includes current detection means for detecting an ion current flowing through the electrode, and is set to determine the distance based on the magnitude of the detected ion current. A spark ignition direct injection engine. In any one of Claims 1 thru | or 5,
The distance data grasping means includes a resistance detecting means for detecting an insulation resistance of the electrode, and is set so as to determine the distance based on the detected insulation resistance. Spark ignition direct injection engine. For each cylinder, there are provided a spark plug with an electrode protruding into the combustion chamber and a multi-hole type fuel injection valve having a plurality of injection holes arranged at the periphery of the combustion chamber and directly injecting fuel into the combustion chamber,
In each cylinder, the axis of some of the plurality of nozzle holes is directed to pass near the tip of the electrode and the extension line thereof,
In a spark ignition direct injection engine in which fuel injection is performed at least in the latter half of the compression stroke to perform stratified combustion in a predetermined operation region that is a low rotation / low load region,
Effective pressure grasping means for grasping a value related to the indicated mean effective pressure for each cylinder;
The fuel injection timing of the cylinder in which the indicated mean effective pressure grasped by the effective pressure grasping means is relatively small in the high load region in the predetermined operation region is relatively advanced compared to the other cylinders. Injection timing correction means for
A spark ignition type direct injection engine characterized by comprising: In claim 8,
The effective pressure grasping means includes angular speed detecting means for detecting an engine angular speed immediately after the explosion process for each cylinder, and is set to determine the indicated mean effective pressure based on the detected angular speed. A spark ignition direct injection engine. In any one of Claims 1 thru | or 9,
The electrode is disposed substantially in the center of the combustion chamber;
The fuel injection valve is disposed at a peripheral portion of the combustion chamber and has, as the plurality of injection holes, other injection holes directed in the piston top surface direction in addition to the specific injection holes,
There are two intake valves for each cylinder,
The fuel injection valve is positioned between the two intake valves;
This is a spark ignition direct injection engine. In any one of Claims 1 thru | or 10,
As the nozzle directed to the vicinity of the electrode, in addition to the specific nozzle, a left nozzle directed to the left side of the electrode, and a right nozzle directed to the right side of the electrode,
The distance from each nozzle of the specific nozzle, left side nozzle and right side nozzle is set to 20 mm or more,
The opening angle formed by the specific nozzle and the left nozzle is set in a range of 15 to 25 degrees, and the fuel spray from the specific nozzle and the fuel spray in a predetermined operation region that is a low rotation / low load region of the engine The fuel spray from the left side nozzle is set to be continuous with each other by the mutual interference effect,
The opening angle formed by the specific nozzle and the right nozzle is set in a range of 15 to 25 degrees, and the fuel spray from the specific 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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