JP2005171866A - Fuel injection control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection control device capable of purifying exhaust gas further by suppressing generation of PM and un-burnt gas. <P>SOLUTION: This device is provided with a first ignition plug 21 having an ignition gap 20 arranged at a center part of the combustion chamber 14, a second ignition plug 23 having an ignition gap 22 arranged with shifting to an exhaust port 17 side, a fuel injection valve 24 directly injecting fuel into the combustion chamber 14 from an opposite side of the second ignition plug 23 with putting the first ignition plug 21 in a middle, a piston 11 have a hollow 27 for increasing fuel injection route from the fuel injection valve 24 to the ignition gap 22 side of the second ignition plug 23 formed thereon, and a control device controlling ignition of the first and the second ignition plug 21, 23 and injection timing of fuel from the fuel injection valve 24 according to a first operation mode igniting only the first ignition plug 21, a second operation mode igniting the first and the second ignition plug 21, 23 and a third operation mode igniting only the second ignition plug 23. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel injection control device for a spark ignition internal combustion engine capable of realizing optimum combustion according to an operation mode of a vehicle.

  As one of methods for improving the fuel consumption of an internal combustion engine, a technique for burning a lean air-fuel mixture by setting the air-fuel ratio to a lean tendency deviating from stoichiometry is known. In this lean combustion technology, the stratified combustion system in which the fuel plug is ignited in a state where the fuel density of the air-fuel mixture interposed around the ignition gap of the spark plug is higher than that of the other part and the air-fuel mixture is burned, It is possible to avoid the risk of misfire in the case of burning a lean air-fuel mixture, and it is possible to adopt not only in an operation region where the engine load is relatively small but also in an operation region where the engine load is larger. What is important in this stratified combustion technology is that an air-fuel mixture containing fuel at a concentration higher than that of the surroundings is formed around the ignition gap of the spark plug, and the air-fuel mixture that becomes lean when viewed as a whole is halfway. This is to ensure that combustion continues without misfire.

  The technology described in Patent Document 1 is provided with a port fuel injection valve used for injecting fuel into an intake port during an intake stroke to form a homogeneous mixture in a combustion chamber, and around an ignition gap of an ignition plug. A cylinder fuel injection valve that directly injects fuel into the combustion chamber just before the end of the compression stroke so as to form an air-fuel mixture containing relatively high density fuel, and the fuel injected from the cylinder fuel injection valve Is formed on the top surface of the piston.

  The technique described in Patent Document 2 is based on the fact that a cylinder fuel injection valve for directly injecting fuel into the combustion chamber during the intake stroke to form a homogeneous mixture in the combustion chamber, and the ignition plug relative to the periphery of the ignition gap. And an in-cylinder fuel injection valve that directly injects fuel into the combustion chamber just before the end of the compression stroke so as to form an air-fuel mixture containing high-density fuel in the cylinder, and ignites the fuel injected from the in-cylinder fuel injection valve A recess for guiding the ignition gap of the plug is formed on the top surface of the piston.

  Audi A3 (model FSI 2.0) has a spark plug ignition gap just before the end of the compression stroke so that a mixture containing relatively high density fuel is formed around the spark plug ignition gap. A low penetrating type in-cylinder fuel injection valve that directly injects fuel toward the vehicle is incorporated.

JP 2002-364409 A JP 2001-214744 A

  In the technique disclosed in Patent Document 1, fuel is injected into the intake port from the port fuel injection valve in the intake stroke, or in the technique disclosed in Patent Document 2, combustion is performed from the in-cylinder fuel injection valve in the intake stroke. When fuel is injected into the chamber to form a homogeneous mixture in the combustion chamber, the mixture may be ignited from the radial center of the combustion chamber due to the symmetry of flame propagation.

  On the other hand, when performing stratified combustion of the air-fuel mixture by directly injecting fuel from the in-cylinder fuel injection valve into the combustion chamber during the compression stroke, the fuel injected from the in-cylinder fuel injection valve is ignited with the air in the combustion chamber. It is necessary to form a recess in the top surface of the piston for winding up to the ignition gap. Moreover, even if such a depression is formed, the length of the fuel injection path from the in-cylinder fuel injection valve to the ignition gap of the ignition plug through the depression of the piston is not sufficient, and in particular, the engine speed is relatively large. In the region, it is difficult to vaporize the fuel completely. As a result, the fuel injected into the combustion chamber during stratified combustion becomes insufficiently vaporized, and unburned gas and fine particles (PM) may be discharged.

  In the Audi A3, fuel is directly injected from the in-cylinder fuel injection valve toward the ignition gap of the spark plug, so that insufficiently vaporized fuel is unlikely to adhere to the top surface of the piston. Emission can be suppressed, and the fluctuation between combustion cycles is small. However, the low penetration type in-cylinder fuel injection valve incorporated in the A3 does not have a function of forming a uniform air-fuel mixture in the entire combustion chamber, so a uniform air-fuel mixture is formed in the entire combustion chamber. In some cases, particularly in an operating region where the engine load is high.

  According to a first aspect of the present invention, there is provided a first spark plug in which an ignition gap is arranged at a radial center portion of a combustion chamber of an internal combustion engine, and an exhaust port that opens to the combustion chamber with respect to the ignition gap of the first spark plug. A second spark plug having an ignition gap biased to the side, an in-cylinder fuel injection valve for directly injecting fuel into the combustion chamber from the opposite side of the second spark plug across the first spark plug, A depression formed on the top surface of the cylinder facing the combustion chamber, and a depression for guiding the fuel injected from the in-cylinder fuel injection valve to the ignition gap side of the second spark plug, and the first and the second in accordance with the operation mode of the vehicle A fuel injection control device comprising a control device for controlling the ignition timing of the second spark plug and the fuel injection timing from the in-cylinder fuel injection valve, wherein the operation mode ignites only the first spark plug. First driving mode When a second operation mode of igniting the first and second spark plugs, is characterized in that a third operating mode of igniting only said second spark plug.

  In the present invention, in the first operation mode, fuel is injected from the in-cylinder fuel injection valve so that a uniform air-fuel mixture is formed in the combustion chamber, and this is burned by the first spark plug. Therefore, it is effective in a region where the engine load is relatively high and a region where the engine speed is relatively large. On the other hand, in the third operation mode, fuel is injected from the in-cylinder fuel injection valve so that an air-fuel mixture having a higher fuel concentration than the surroundings is formed near the ignition gap of the second spark plug, and this is stratified by the second spark plug. Burn. Therefore, it is effective in a region where the engine load is relatively small and a region where the engine speed is relatively slow. In this case, the fuel injection path from the in-cylinder fuel injection valve to the ignition gap of the second spark plug through the recess is arranged so as to be biased toward the exhaust port side where the ignition gap of the second spark plug opens into the combustion chamber. Therefore, the injection path is longer than that of the conventional one, and fuel vaporization is further promoted. In the second operation mode, the first and second spark plugs are used, which is effective in a region where the engine load and the engine speed are intermediate between the first operation mode and the third operation mode.

  In the fuel injection control device according to the first aspect of the present invention, it is preferable that the fuel injection timing from the in-cylinder fuel injection valve in the second operation mode is set to the intake stroke and the compression stroke.

  A port fuel injection valve for injecting fuel into an intake passage communicating with the combustion chamber is further provided. At least one of the in-cylinder and the port fuel injection valve is used in the first operation mode, and at least the in-cylinder fuel injection valve is used as the second fuel injection valve. The operation mode can be used. In this case, if the port fuel injection valve is used together with the in-cylinder fuel injection valve in the second operation mode, it is preferable to set the fuel injection timing from the in-cylinder fuel injection valve to the compression stroke.

  It is preferable that the fuel injection timing from the in-cylinder fuel injection valve in the first operation mode is set to the intake stroke.

  It is preferable that the fuel injection timing from the in-cylinder fuel injection valve in the third operation mode is set to the compression stroke.

  According to a second aspect of the present invention, there is provided a first spark plug in which an ignition gap is disposed at a radial center portion of a combustion chamber of an internal combustion engine, and an intake port that opens into the combustion chamber with respect to the ignition gap of the first spark plug. A second spark plug having an ignition gap biased to the side, and fuel in the combustion chamber from the opposite side of the first spark plug across the second spark plug toward the ignition gap of the second spark plug In-cylinder fuel injection valve for direct injection, port fuel injection valve for injecting fuel into an intake passage communicating with the combustion chamber, ignition of the first and second spark plugs and the cylinder according to the operation mode of the vehicle A fuel injection control device including a control device for controlling the timing of fuel injection from the port fuel injection valve, wherein the operation mode is a first using the first spark plug and the port fuel injection valve. Driving A second operation mode using the first and second spark plugs and the in-cylinder, port fuel injection valve, and a third operation using the second ignition plug and the in-cylinder fuel injection valve. And a mode.

  In the present invention, in the first operation mode, the first spark plug and the port fuel injection valve are used, and a uniform air-fuel mixture is formed in the combustion chamber and burned by the first spark plug, so that the engine load is high. This is effective in areas where engine speed is high. On the other hand, in the third operation mode, the second spark plug and the in-cylinder fuel injection valve are used, and the fuel injected from the in-cylinder fuel injection valve is supplied together with air around the ignition gap of the second ignition plug to perform stratified combustion. Therefore, it is effective in an area where the engine load is small and an engine speed is low. In the second operation mode, the first and second spark plugs and the in-cylinder and port fuel injection valves are used, and are effective in an intermediate operation state between the first operation mode and the third operation mode.

  In the fuel injection control device according to the second aspect of the present invention, it is preferable that the fuel injection timing from the in-cylinder fuel injection valve in the second and third operation modes is set to the compression stroke.

  The in-cylinder fuel injection valve is preferably a low-penetration type fuel injection valve that has a short injection distance after a predetermined time has elapsed since the fuel was injected.

  In the fuel injection control apparatus according to the first and second embodiments of the present invention, the first and second spark plugs may be integrated with these main bodies.

  According to the fuel injection control device of the first aspect of the present invention, the first spark plug in which the ignition gap is arranged at the radial center of the combustion chamber of the internal combustion engine, and the combustion chamber with respect to the ignition gap of the first spark plug A second spark plug that is biased toward the exhaust port that opens to the exhaust port, and an in-cylinder fuel injection valve that directly injects fuel into the combustion chamber from the opposite side of the second spark plug across the first spark plug; And a piston having a recess formed on the top surface facing the combustion chamber for guiding the fuel injected from the in-cylinder fuel injection valve to the ignition gap side of the second spark plug. Since the spark plug and the in-cylinder fuel injection valve are used, the injection path from the in-cylinder fuel injection valve to the second spark plug through the depression of the piston is longer than the conventional one when performing stratified combustion. Is injected from the cylinder fuel injection valve. The vaporization of the fuel can be promoted. As a result, it is possible to further purify the exhaust gas while suppressing the generation of unburned gas and PM.

  When the fuel injection timing from the in-cylinder fuel injection valve in the second operation mode is set to the intake stroke and the compression stroke, combustion having characteristics intermediate between the first operation mode and the third operation mode is realized. When the operation mode is switched between the first operation mode and the third operation mode, a sudden torque fluctuation can be suppressed by interposing the second operation mode.

  When the port fuel injection valve is used together with the in-cylinder fuel injection valve in the second operation mode and the fuel injection timing from the in-cylinder fuel injection valve is set to the compression stroke, the first operation mode and the third operation mode Combustion having characteristics intermediate to the operation mode can be realized, and by interposing the second operation mode when switching the operation mode between the first operation mode and the third operation mode, It is possible to suppress sudden torque fluctuations.

  In the first operation mode, when fuel is injected from the in-cylinder fuel injection valve in the intake stroke, the fuel injected from the in-cylinder fuel injection valve is made more uniform in the combustion chamber by the intake air flowing into the combustion chamber from the intake port. Can be mixed.

  When only the in-cylinder fuel injection valve is used in the second operation mode, by injecting fuel from the in-cylinder fuel injection valve in the intake stroke and the compression stroke, the first operation mode, the third operation mode, Combustion having an intermediate characteristic between the first operation mode and the third operation mode can be realized by interposing the second operation mode when the operation mode is switched between the first operation mode and the third operation mode. It is possible to suppress fluctuations.

  In the third operation mode, when fuel is injected from the in-cylinder fuel injection valve in the compression stroke, a long injection path from the in-cylinder fuel injection valve to the second spark plug through the depression of the piston when performing stratified combustion Is defined, and the vaporization of the fuel injected from the in-cylinder fuel injection valve can be promoted. As a result, it is possible to further purify the exhaust gas while suppressing the generation of unburned gas and PM.

  According to the fuel injection control device of the second aspect of the present invention, the first spark plug in which the ignition gap is arranged at the radial center of the combustion chamber of the internal combustion engine, and the combustion chamber with respect to the ignition gap of the first spark plug And a second spark plug that is biased toward the intake port that opens toward the intake port, and the opposite side of the first spark plug across the second spark plug toward the ignition gap of the second spark plug. An in-cylinder fuel injection valve that directly injects fuel and a port fuel injection valve that injects fuel into an intake passage communicating with the combustion chamber. The first spark plug and the port fuel injection valve are used in the first operation mode. As a result, a uniform air-fuel mixture can be formed in the combustion chamber, and this can be reliably burned by the first spark plug. Further, since the second spark plug and the in-cylinder fuel injection valve are used in the third operation mode, the fuel injected from the in-cylinder fuel injection valve is in the vicinity of the ignition gap of the second spark plug. An air-fuel mixture having a higher fuel density than the surroundings is formed, and stratified combustion can be realized by ignition of the second spark plug. In addition, the fuel injected from the in-cylinder fuel injection valve is less likely to adhere to the top surface of the piston, and the exhaust gas can be further purified by suppressing the generation of unburned gas and PM.

  In the second and third operation modes, when fuel is injected from the in-cylinder fuel injection valve in the compression stroke, an air-fuel mixture having a relatively higher fuel density than the surrounding area is present in the vicinity of the ignition gap of the second spark plug. Formed and can be stratified by the second spark plug. In addition, the fuel injected from the in-cylinder fuel injection valve is less likely to adhere to the top surface of the piston, and the exhaust gas can be further purified by suppressing the generation of unburned gas and PM.

  In the case of a low penetrating injection valve that has a short injection distance after a predetermined time has elapsed since the in-cylinder fuel injection valve injected fuel, in-cylinder fuel injection without forming a depression or the like on the top surface of the piston It is possible to realize stratified combustion by reliably interposing the fuel injected from the valve around the ignition gap of the second spark plug.

  When the main bodies of the first and second spark plugs are integrated, the occupied space for installing the spark plug can be further narrowed.

  Embodiments in which the fuel injection control device according to the present invention is applied to a spark ignition internal combustion engine will be described in detail with reference to FIGS. 1 to 7. However, the present invention is not limited to such embodiments, and All changes and modifications encompassed within the scope of the inventive concept described in the scope are possible, and of course can be applied to any other technique belonging to the spirit of the invention.

  FIG. 1 shows a schematic configuration according to an embodiment of a fuel injection control device corresponding to the first embodiment of the present invention, FIG. 2 shows a sectional view taken along the line II-II, and FIG. 3 shows a control block thereof. . That is, a cylinder head 15 that defines a combustion chamber 14 is attached to a cylinder block 13 that forms a cylinder 12 into which the piston 11 is slidably fitted.

  In the cylinder head 15, a pair of intake ports 16 and a pair of exhaust ports 17 are formed so as to face the combustion chamber 14, and an intake valve 18 that opens and closes the open end of the intake port 16 and the open end of the exhaust port 17. The exhaust valve 19 reciprocates at a predetermined timing in conjunction with the reciprocating motion of the piston 11, that is, the rotational motion of a crankshaft (not shown), so that the communication state of the intake port 16 and the exhaust port 17 with respect to the combustion chamber 14 is switched. It is supposed to be.

  The cylinder head 15 has a first spark plug 21 disposed so that the ignition gap 20 faces the radial center of the combustion chamber 14, and the first spark plug (hereinafter referred to as a center side plug). A second spark plug (hereinafter referred to as an exhaust side plug) 23 is attached so that the ignition gap 22 is positioned closer to the exhaust port 17 than the ignition gap 20 of the engine 21. A high voltage is applied to the ignition gaps 20 and 22 of the two spark plugs 21 and 23 at a predetermined timing in conjunction with the reciprocating motion of the piston 11, that is, the rotational motion of a crankshaft (not shown). Are to be performed independently.

  Further, the cylinder head 15 has a combustion chamber 14 on the opposite side of the exhaust side plug 23 with the center side plug 21 sandwiched between the center side and the ignition gaps 20 and 22 of the exhaust side plugs 21 and 23. An in-cylinder fuel injection valve 24 for directly injecting fuel into the combustion chamber 14 from the outer peripheral edge is provided. This in-cylinder fuel injection valve (hereinafter abbreviated as “in-cylinder injection valve”) 24 can directly inject fuel into the combustion chamber 14 at a predetermined timing in conjunction with the reciprocating motion of the piston 11. A port fuel injection valve 25 for injecting fuel into the intake port 16 is also attached to the cylinder head 15. This port fuel injection valve (hereinafter abbreviated as a port injection valve) 25 receives fuel during the intake stroke. Since it is set to inject into the intake port 16, the fuel injected from the port injection valve 25 is sucked into the combustion chamber 14 together with the intake air through the intake port 16.

  The top surface 26 of the piston 11 that reciprocates in the cylinder 12 is formed with a recess 27 extending along the direction connecting the in-cylinder injection valve 24 and the ignition gap 22 of the exhaust side plug 23. When the fuel is injected from the in-cylinder injection valve 24 toward the top surface 26 of the piston 11 just before the end of the compression stroke of the piston 11, the recess 27 is a fuel along a plane including the axis of the cylinder 12 in the combustion chamber 14. 1, that is, a swirling flow of fuel in the vertical direction in FIG. 1, and becomes a fuel injection flow path for forming a relatively high density region of fuel in the vicinity of the ignition gap 22 of the exhaust side plug 23. . That is, when fuel is injected from the in-cylinder injection valve 24 toward the recess 27 just before the end of the compression stroke of the piston 11, the fuel is discharged from the exhaust plug 23 by the vertical wall 28 of the recess 27 facing the in-cylinder injection valve 24. A region that is led to the vicinity of the ignition gap 22 and has a relatively high fuel density with respect to the surroundings is formed, and in combination with the promotion of vaporization due to the lengthening of the fuel path from the in-cylinder injection valve 24 to the ignition gap 22, The ignitability of the fuel at the time of combustion can be improved.

  Two types of fuel injection timings from the in-cylinder injection valve 24 and the port injection valve 25 in the present embodiment are set. That is, one of them corresponds to a low load operation in which the amount of depression of an accelerator pedal (not shown) operated by the driver is relatively small, and the fuel is injected so that the fuel tends to lean just before the end of the compression stroke of the piston 11. Thus, a region having a relatively high fuel density is formed around the ignition gap 22 of the exhaust plug 23 to realize stratified combustion. The other is for high load operation where the amount of depression of the accelerator pedal is relatively large. During the intake stroke of the piston 11, the fuel is injected into the combustion chamber 14 so as to be stoichiometric, and the entire combustion chamber 14 is In this way, the fuel is uniformly dispersed to achieve so-called homogeneous combustion.

  When the in-cylinder injection valve 24 is used in the present embodiment, fuel is injected from the in-cylinder injection valve 24 at the end of the compression stroke, and the port injection valve 25 injects fuel into the intake port 16 during the intake stroke. However, the amount of fuel injected from the cylinder and the port injection valves 24 and 25, the injection timing thereof, the ignition timing of the center side and the exhaust side plugs 21 and 23, etc. are depressed by an accelerator pedal (not shown) which is depressed by the driver. Based on the detection signal from the accelerator opening sensor 29 that detects the amount, the detection signal from the vehicle speed sensor 30 that detects the traveling speed of the vehicle, and the detection signal from the crank angle sensor 31 that detects the rotation phase of the crankshaft. The controller 32 is controlled under conditions set in advance.

  Specifically, there are three operation modes corresponding to a region where the engine load is low, a region where the engine load is high, and a region where the engine load is intermediate between these regions. The first operation mode corresponds to the high load region of the engine, fuel is injected from the port injection valve 25 in the intake stroke of the piston 11, and a uniform air-fuel mixture is generated in the combustion chamber 14 together with the intake air flowing in the intake port 16. To achieve the homogeneous combustion described above. The third operation mode corresponds to a low load region of the engine, and fuel is injected from the in-cylinder injection valve 24 just before the end of the compression stroke of the piston 11 and compared with the periphery of the ignition gap 20 of the central plug 21. A region with a high fuel density is formed, and stratified combustion is realized so that the fuel tends to be lean as a whole. The second operation mode corresponds to an intermediate region between the first operation mode and the third operation mode. Table 1 below shows the relationship among these three operation modes, the used fuel injection valve, the used ignition plug, and its combustion characteristics.

  Here, semi-stratified combustion refers to an intermediate state between homogeneous combustion and stratified combustion, and smoothes the output change of the engine when the operation mode is switched between the first operation mode and the third operation mode. It can be said that it is a transient operation mode. Therefore, depending on the output characteristics of the engine and the characteristics of the vehicle, it is possible to omit the second operation mode and set only two operation modes, the first operation mode and the third operation mode.

  The in-cylinder injection valve 24 may be used together with the port injection valve 25 in the first operation mode described above, and the in-cylinder injection valve 24 may be operated during the intake stroke to inject fuel into the combustion chamber 14. Alternatively, it is possible to omit the port injection valve 25 and use only the in-cylinder injection valve 24. In this case, in the first operation mode, fuel is injected from the in-cylinder injection valve 24 in the intake stroke, and in the second operation mode, fuel is injected from the in-cylinder injection valve 24 in both the intake stroke and the compression stroke. In the operation mode, the fuel may be injected from the in-cylinder injection valve 24 in the compression stroke. In this way, when the fuel is supplied into the combustion chamber 14 using only the in-cylinder injection valve 24, the port injection valve 25 can be omitted, so that the cost can be reduced. In any case, when fuel is injected from the in-cylinder injection valve 24 in the compression stroke, it is effective in realizing stratified combustion that the fuel is injected just before the end of the compression stroke.

  It is also possible to employ a multi-electrode type ignition plug in which the above-described center side plug 21 and exhaust side plug 23 are integrated, and FIG. 4 shows a schematic configuration similar to FIG. 1 in the previous embodiment. The same reference numerals are used for elements having the same function, and redundant description is omitted. That is, a multi-electrode type ignition plug 33 having two ignition gaps 20 and 22 is attached to the cylinder head 15, and in this case, one ignition gap 20 is located in the radial center of the combustion chamber 14, and the other The ignition plug 33 is fixed to the cylinder head 15 so that the ignition gap 22 is positioned on the exhaust port 17 side. The ignition timing for these two ignition gaps 20 and 22 may be the same as in the above-described embodiment, but both can be ignited at the same time.

  In the two embodiments described above, the depression 27 is formed in the top surface 26 of the piston 11, and the fuel injected from the in-cylinder injection valve 24 is caused to flow along the depression 27, so that the ignition gap 22 of the exhaust side plug 23 is formed. By guiding and elongating the fuel injection path, the vaporization is promoted. However, by forming the recess 27 in the piston 11, a part of the fuel adheres to the recess 27 without being evaporated, In order to reduce the content ratio of unburned gas and PM in the exhaust gas, the fuel may be directly injected from the in-cylinder injection valve 24 toward the ignition gap of the ignition plug.

  FIG. 5 shows a schematic configuration of one embodiment of the fuel injection control apparatus according to the second embodiment of the present invention, and FIG. 6 shows a sectional view taken along the line VI-VI. These elements are given the same reference numerals, and redundant explanations are omitted. That is, the cylinder head 15 is ignited on the side of the intake port 16 with respect to the center side plug 21 disposed so that the ignition gap 20 faces the radial center of the combustion chamber 14 and the ignition gap 20 of the center side plug 21. An intake side plug 35 is attached so that the gap 34 is positioned. A high voltage is applied to the ignition gaps 20 and 33 of the two spark plugs 21 and 34 at a predetermined timing in conjunction with the reciprocating motion of the piston 11, that is, the rotational motion of a crankshaft (not shown). Are to be performed independently.

  In addition, the cylinder head 15 has a combustion chamber 14 on the opposite side of the central plug 21 with the intake side plug 35 interposed therebetween so as to be aligned with the ignition gaps 20 and 33 of the central side and the intake side plugs 21 and 34. An in-cylinder injection valve 24 that directly injects fuel into the combustion chamber 14 from the outer peripheral edge of the cylinder is provided. This in-cylinder injection valve 24 is of a so-called low penetration force type in which the fuel injection reach distance is short after a predetermined time has elapsed since the fuel was injected, and the flying energy at the initial stage of injection suddenly decreases after a predetermined time. An example of the injection characteristic is shown in the logarithmic graph of FIG. FIG. 7 shows the relationship between the elapsed time from the time of fuel injection and the flight distance of the fuel. The fuel that moves linearly at a constant speed immediately after injection loses energy and is fluidized along with the intake air in the combustion chamber 14. Indicates to exercise. In the present embodiment, the injection characteristic of the in-cylinder injection valve 24 is adjusted so that the fuel flight distance corresponding to the inflection point P of the graph is about 40% or less of the bore diameter. By using such an in-cylinder injection valve 24 and directly injecting fuel toward the ignition gap 34 of the intake side plug 35 immediately before the end of the compression stroke in the second and third operation modes, the in-cylinder injection valve The fuel injected from 24 can be directly interposed in the vicinity of the ignition gap 34 of the intake side plug 35, and stratified combustion can be realized.

  Thus, by using the low penetration force type in-cylinder injection valve 24, it is not necessary to form the depression 27 as in the previous two embodiments on the top surface 26 of the piston 11, and the top surface 26 is smoothed. The fuel injected from the in-cylinder injection valve 24 is less likely to adhere to the top surface 26 of the piston 11, and the exhaust gas can be further purified by suppressing the generation of unburned gas and PM. is there.

  Table 2 below shows the relationship among the three operation modes, the used fuel injection valve, the used spark plug, and the combustion characteristics thereof in the present embodiment.

  The first operation mode in the present embodiment corresponds to the high load region of the engine as in the previous embodiment, and fuel is injected from the port injection valve 25 in the intake stroke of the piston 11 and flows in the intake port 16. A uniform air-fuel mixture is formed in the combustion chamber 14 together with the intake air to realize the above-described homogeneous combustion. On the other hand, the third operation mode corresponds to a low load region of the engine, and fuel is injected from the in-cylinder injection valve 24 just before the end of the compression stroke of the piston 11 and compared with the periphery of the ignition gap 34 of the intake side plug 35. A region with a high fuel density is formed, and stratified combustion is realized so that the fuel tends to be lean as a whole. The second operation mode corresponds to an intermediate region between the first operation mode and the third operation mode.

It is sectional drawing showing the schematic structure of one Embodiment which applied the fuel-injection control apparatus by this invention to the spark ignition internal combustion engine. It is II-II arrow sectional drawing in FIG. FIG. 2 is a control block diagram in the embodiment shown in FIG. 1. It is sectional drawing showing schematic structure of other embodiment which integrated the integral spark plug in the fuel-injection control apparatus by this invention. It is sectional drawing showing the schematic structure of another embodiment which applied the fuel-injection control apparatus by this invention to the spark ignition internal combustion engine. It is VI-VI arrow sectional drawing in FIG. It is a graph showing the fuel-injection characteristic of the cylinder injection valve shown in FIG.

Explanation of symbols

11 Piston 12 Cylinder 13 Cylinder Block 14 Combustion Chamber 15 Cylinder Head 16 Intake Port 17 Exhaust Port 18 Intake Valve 19 Exhaust Valve 20 Ignition Gap 21 First Spark Plug (Center Side Plug)
22 Ignition gap 23 Second spark plug (exhaust side plug)
24 In-cylinder fuel injection valve (in-cylinder injection valve)
25 port fuel injection valve (port injection valve)
26 Top surface 27 Dimple 28 Vertical wall 29 Accelerator opening sensor 30 Vehicle speed sensor 31 Crank angle sensor 32 Controller 33 Spark plug 34 Spark gap 35 Intake side plug

Claims (10)

A first spark plug in which an ignition gap is arranged in a radially central portion of the combustion chamber of the internal combustion engine;
A second spark plug in which an ignition gap is arranged with a bias toward the exhaust port opening to the combustion chamber with respect to the ignition gap of the first spark plug;
An in-cylinder fuel injection valve that directly injects fuel into the combustion chamber from the opposite side of the second spark plug across the first spark plug;
A piston having a recess formed on the top surface facing the combustion chamber, the recess for guiding the fuel injected from the in-cylinder fuel injection valve to the ignition gap side of the second spark plug;
A fuel injection control device comprising: a control device that controls ignition timing of the first and second spark plugs and fuel injection timing from the in-cylinder fuel injection valve in accordance with an operation mode of a vehicle, Includes a first operation mode for igniting only the first spark plug, a second operation mode for igniting the first and second spark plugs, and a third operation mode for igniting only the second spark plug. And a fuel injection control device.   2. The fuel injection control device according to claim 1, wherein the fuel injection timing from the in-cylinder fuel injection valve in the second operation mode is set to an intake stroke and a compression stroke. 3. A port fuel injection valve for injecting fuel into an intake passage communicating with the combustion chamber;
At least one of the in-cylinder and port fuel injection valves is used in the first operation mode;
The fuel injection control device according to claim 1, wherein at least the in-cylinder fuel injection valve is used in the second operation mode.   The fuel injection timing from the in-cylinder fuel injection valve is set to a compression stroke when a port fuel injection valve is used together with the in-cylinder fuel injection valve in the second operation mode. Item 4. The fuel injection control device according to Item 3.   The fuel injection control device according to any one of claims 1 to 4, wherein a fuel injection timing from the in-cylinder fuel injection valve in the first operation mode is set to an intake stroke.   The fuel injection control device according to any one of claims 1 to 5, wherein the fuel injection timing from the in-cylinder fuel injection valve in the third operation mode is set to a compression stroke. A first spark plug in which an ignition gap is arranged in a radially central portion of the combustion chamber of the internal combustion engine;
A second spark plug in which an ignition gap is arranged with a bias toward the intake port opening to the combustion chamber with respect to the first spark plug;
An in-cylinder fuel injection valve that directly injects fuel into the combustion chamber from the opposite side of the first spark plug to the ignition gap of the second spark plug across the second spark plug;
A port fuel injection valve for injecting fuel into an intake passage communicating with the combustion chamber;
A fuel injection control device comprising: a control device for controlling ignition timing of the first and second spark plugs and fuel injection timing from the in-cylinder and port fuel injection valves in accordance with a driving mode of the vehicle, The operation mode includes a first operation mode using the first spark plug and the port fuel injection valve, and a second operation mode using the first and second ignition plugs and the in-cylinder and port fuel injection valve. And a third operation mode using the second spark plug and the in-cylinder fuel injection valve.   The fuel injection control device according to claim 7, wherein the fuel injection timing from the in-cylinder fuel injection valve in the second and third operation modes is set to a compression stroke.   9. The in-cylinder fuel injection valve is a low penetrating force type fuel injection valve having a short fuel injection arrival distance after a predetermined time has elapsed since the fuel was injected. Fuel injection control device. The fuel injection control device according to any one of claims 1 to 9, wherein the first and second spark plugs are obtained by integrating these main bodies.

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