JP2014009629A - Fuel injection valve of direct-injection engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection valve of a direct-injection engine which unites lowering of suction power of solenoid coils 81, 82 necessary for the valve opening by reducing back pressure of a needle 83 and enlarging of arrangement intervals of a number of nozzle holes 84, in the fuel injection valve (injector 80) of a solenoid driving type.SOLUTION: A fuel injection valve includes valve bodies 841, 842 having fuel passages 800 and a plurality of nozzle holes, a needle which is stroked so as to open and close the respective nozzle holes in the fuel passages and solenoid coils 81, 82 which are arranged outside the fuel passages and stroke the needle so as to open the respective nozzle holes upon electric conduction. The maximum fuel pressure in the fuel passages is set to high fuel pressure of 40 MPa or more. The fuel passage includes a sheet part 801 which is set smaller than the diameter of a basic cylindrical part at the tip part of the needle, a throttle part 802 which continues to the sheet part and an enlargement part 803 which continues to the throttle part and has a diameter larger than the throttle part. Therein, the plurality of nozzle holes are communicated with the enlargement part.

Description

  The technology disclosed herein relates to a fuel injection valve for a direct injection engine.

  Patent Document 1 discloses a solenoid-driven fuel injection valve configured to stroke a needle disposed in a fuel passage by sucking a movable core by energization of a solenoid coil, thereby opening and closing a nozzle. In order to reduce the back pressure acting on the needle due to the fuel pressure in the fuel passage by reducing the diameter of the seat portion on which the tip of the needle is seated, the suction of the solenoid coil necessary to open the needle Techniques that reduce power are described.

JP 2009-257309 A

  Reducing the diameter of the seat portion on which the tip of the needle is seated is particularly effective in reducing the suction force when the valve is opened, for example, when the fuel pressure is set high in order to achieve a high injection rate. is there. On the other hand, in order to achieve a high injection rate, the fuel pressure is set high, and when trying to increase the number of nozzles of the fuel injection valve, the seat portion is made smaller so that it continues to this small diameter seat portion. A large number of nozzle holes must be communicated with the small diameter flow path. This is disadvantageous for atomization of the fuel injected through the nozzle hole by narrowing the interval between the nozzle holes opened at the tip of the fuel injection valve.

  The technology disclosed herein has been made in view of such a point, and an object thereof is to open a solenoid-driven fuel injection valve including a needle by reducing the back pressure of the needle. The purpose is to reduce both the suction force of the solenoid coil necessary for the valve and to increase the arrangement interval of many nozzle holes.

  The technology disclosed herein relates to a fuel injection valve of a direct injection engine that directly injects fuel containing gasoline into a cylinder of the engine.

  The fuel injection valve has a fuel passage provided therein, a valve body having a plurality of injection holes provided at a tip portion thereof, and is disposed in the fuel passage and opens and closes the injection holes. And a solenoid coil that is disposed outside the fuel passage and strokes the needle so that the needle opens the nozzle holes when energized.

  Thus, the maximum fuel pressure in the fuel passage is set to a high fuel pressure of 40 MPa or more, the fuel passage is set to a diameter smaller than the diameter of the basic cylindrical portion at the tip portion of the needle, and the tip portion is A seat part that opens and closes each nozzle hole by seating and separating; a throttle part that is continuous with the sheet part; and an enlarged part that is continuous with the throttle part and has a diameter larger than that of the throttle part. The plurality of nozzle holes communicate with the enlarged portion.

  According to this configuration, when the maximum fuel pressure in the fuel passage is set to a high fuel pressure of 40 MPa or higher, a high back pressure acts on the needle disposed in the fuel passage in the seated state. obtain. In the above configuration, the seat portion on which the tip end portion of the needle is seated and separated is set to have a smaller diameter than the diameter of the basic cylindrical portion at the tip end portion of the needle, so that the back acting on the needle even at high fuel pressure. The pressure is reduced by the amount by which the diameter of the sheet portion is reduced. This reduces the suction force required for opening the needle, which is advantageous for downsizing the solenoid coil and saving power consumption. The miniaturization of the solenoid coil also enables the fuel injection valve to be reduced in diameter, which is advantageous for mounting on the cylinder head of the engine.

  On the other hand, the throttle portion that is continuous with the sheet portion can have a relatively small diameter corresponding to the small diameter sheet portion. The narrowed portion may have the same diameter as the seat portion or a smaller diameter than the seat portion. Thus, by continuously providing an enlarged portion having a diameter larger than that of the throttle portion, the plurality of nozzle holes can communicate with the enlarged portion having a large diameter instead of the throttle portion having a small diameter. It becomes possible. This makes it possible to widen the interval between the nozzle holes opened at the tip of the valve body. Thus, the fuel injection valve having the above-described configuration combines a high fuel pressure and a plurality of injection holes arranged at sufficient intervals to ensure atomization of fuel containing gasoline and a high injection rate. To achieve a good air-fuel mixture in the cylinder of the engine.

  The tip of the needle may be formed to be tapered, and the needle may be configured such that an intermediate portion of the tapered tip is seated on the seat portion.

  This is advantageous for reducing the diameter of the seat portion, and when the needle is separated from the seat portion, the flow resistance of the fuel flowing between the inclined needle tip surface and the seat portion is reduced, and the seat As a result of the increase in the fuel pressure on the throttle portion side continuous with the portion, a force in the valve opening direction acts on the needle, and the suction force required at the time of valve opening decreases.

  The direct injection engine may be configured to compress and ignite a homogeneous lean air-fuel mixture in a predetermined operating region.

  As described above, ensuring fuel atomization in a fuel injection valve having a plurality of injection holes is advantageous for forming a homogeneous lean air-fuel mixture, and compression ignition combustion is stabilized.

  As described above, according to the fuel injection valve of the direct injection engine, by setting the diameter of the seat portion in the fuel passage to be smaller than the diameter of the basic cylindrical portion at the tip portion of the needle, Even if the fuel pressure is set to a high fuel pressure of 40 MPa or more, the back pressure acting on the needle can be reduced. This reduces the suction force required for opening the needle, which is advantageous for downsizing the solenoid coil and saving power consumption. On the other hand, the enlarged portion that communicates with the seat portion via the throttle portion has a diameter larger than that of the throttle portion, so that a plurality of nozzle holes communicate with the enlarged portion to open the tip of the valve body. It is possible to widen the interval between each other. This makes it possible to ensure the atomization of the fuel containing gasoline, and in combination with the high fuel pressure, a good air-fuel mixture can be formed in the cylinder of the engine.

It is the schematic which shows the structure of a spark ignition direct injection gasoline engine. It is a block diagram concerning control of a spark ignition direct injection gasoline engine. It is a figure which illustrates the operating area of an engine. (A) Illustration of fuel injection timing and ignition timing in retard injection, and illustration of heat generation rate thereby, (b) Illustration of fuel injection timing and ignition timing in intake stroke injection, and illustration of heat generation rate thereby . It is sectional drawing which shows the structure of an injector. It is a figure which compares the characteristic of the big stroke and small stroke of an injector. It is sectional drawing which expands and shows the structure of the 1st solenoid coil vicinity of an injector. 5A is a view showing a lift state of a movable core when only the first solenoid coil is energized, and FIG. 5B is a diagram showing a lift state of the movable core when only the second solenoid coil is energized. is there. It is sectional drawing which shows the injector of a structure different from FIG. In the injector shown in FIG. 9, (a) the movable core is lifted when only the first solenoid coil is energized, and (b) the movable core is lifted when only the second solenoid coil is energized. is there. (A) It is sectional drawing which expands and shows the structure of the front-end | tip part of an injector, (b) It is a bottom view which illustrates arrangement | positioning of the nozzle hole provided in the injector. It is a bottom view which shows another example of arrangement | positioning of a nozzle hole. It is the schematic which shows the arrangement | positioning relationship and connection relationship of an engine and a high pressure fuel pump. It is sectional drawing which shows the structure of a high pressure fuel pump, (a) is the state in which a plunger is located in a top dead center, (b) is the state in which a plunger is located in a bottom dead center, (c) is c- It is c sectional drawing. It is sectional drawing which expands and shows the structure of the suction valve vicinity in a high pressure fuel pump.

  Hereinafter, embodiments will be described with reference to the drawings. The description of the following embodiment is an example. 1 and 2 show a schematic configuration of the engine 1. The engine 1 is a spark ignition type four-cycle engine which is mounted on a vehicle and supplied with fuel containing at least gasoline (specifically, gasoline or a mixed fuel of gasoline and alcohol (E25, etc.)). is there. The engine 1 is provided with a cylinder block 11 provided with a plurality of cylinders 18 (only one shown), a cylinder head 12 provided on the cylinder block 11, and a cylinder block 11 below the cylinder block 11. And an oil pan 13 in which oil is stored. In the engine 1 of this example, although not shown, four cylinders 18 are arranged in a row. A piston 14 connected to the crankshaft 15 via a connecting rod 142 is fitted in each cylinder 18 so as to be able to reciprocate. A cavity 141 like a reentrant type in a diesel engine is formed on the top surface of the piston 14. The cavity 141 is opposed to an injector 80 described later when the piston 14 is positioned near the compression top dead center.

  The cylinder head 12, the cylinder 18 and the piston 14 having the cavity 141 define a combustion chamber. The shape of the combustion chamber is not limited to the shape illustrated. For example, the shape of the cavity 141, the top surface shape of the piston 14, the shape of the ceiling portion of the combustion chamber, and the like can be changed as appropriate.

  The engine 1 is set to a relatively high geometric compression ratio of 15 or more for the purpose of improving the theoretical thermal efficiency and stabilizing the compression ignition combustion described later. In addition, what is necessary is just to set a geometric compression ratio suitably in the range of about 15-20.

  The cylinder head 12 is formed with an intake port 16 and an exhaust port 17 for each cylinder 18. The intake port 16 and the exhaust port 17 include an intake valve 21 and an exhaust valve that open and close the opening on the combustion chamber side. 22 are arranged respectively.

  Among the valve systems that drive the intake valve 21 and the exhaust valve 22, respectively, on the exhaust side, the operation mode of the exhaust valve 22 is switched between a normal mode and a special mode, for example, a hydraulically operated variable mechanism (see FIG. 2). Hereinafter, a VVL (Variable Valve Lift) 71 is provided. Although the detailed illustration of the configuration of the VVL 71 is omitted, two types of cams having different cam profiles, a first cam having one cam peak and a second cam having two cam peaks, and the first And a lost motion mechanism that selectively transmits an operating state of one of the second cams to the exhaust valve. When the operating state of the first cam is transmitted to the exhaust valve 22, the exhaust valve 22 operates in the normal mode in which the valve is opened only once during the exhaust stroke, whereas the operating state of the second cam is the exhaust valve. When transmitting to the engine 22, the exhaust valve 22 operates in a special mode in which the exhaust valve is opened during the exhaust stroke and is also opened during the intake stroke so that the exhaust is opened twice. The normal mode and the special mode of the VVL 71 are switched according to the operating state of the engine. Specifically, the special mode is used in the control related to the internal EGR. In order to enable switching between the normal mode and the special mode, an electromagnetically driven valve system that drives the exhaust valve 22 by an electromagnetic actuator may be employed.

  The exhaust-side valve system is also provided with a phase variable mechanism (hereinafter referred to as VVT (Variable Valve Timing)) 74 that can change the rotational phase of the exhaust camshaft with respect to the crankshaft 15. The VVT 74 may employ a hydraulic, electromagnetic, or mechanical structure as appropriate, and illustration of the detailed structure is omitted.

  As shown in FIG. 2, the lift side variable mechanism capable of continuously changing the lift amounts of the VVT 72 and the intake valve 21 on the intake side as compared to the exhaust side valve system having the VVL 71 and VVT 74. (Hereinafter referred to as CVVL (Continuously Variable Valve Lift)) 73. The CVVL 73 can adopt various known structures as appropriate, and illustration of the detailed structure is omitted. By the VVT 72 and the CVVL 73, the intake valve 21 can change its valve opening timing, valve closing timing, and lift amount.

  The cylinder head 12 is also provided with an injector 80 that directly injects fuel into the cylinder 18 for each cylinder 18. The injector 80 is disposed such that its nozzle hole faces the combustion chamber from the center portion of the ceiling surface of the combustion chamber. The injector 80 directly injects an amount of fuel corresponding to the operation state of the engine 1 at an injection timing according to the operation state of the engine 1 into the combustion chamber. In this example, the injector 80 is a multi-hole type injector having a plurality of nozzle holes. Thereby, the injector 80 injects the fuel so that the fuel spray spreads radially. Details of the configuration of the injector 80 will be described later.

  A fuel tank (not shown) and the injector 80 are connected to each other by a fuel supply path. A fuel supply system 62 including a high-pressure fuel pump 90 and a fuel rail 64 and capable of supplying fuel to the injector 80 at a relatively high fuel pressure is interposed on the fuel supply path. The high-pressure fuel pump 90 pumps fuel from the fuel tank to the fuel rail 64, and the fuel rail 64 can store the pumped fuel at a relatively high fuel pressure. When the injector 80 is opened, the fuel stored in the fuel rail 64 is injected from the injection port of the injector 80. The high-pressure fuel pump 90 is a plunger type pump, which will be described in detail later, and is driven by the engine 1. The fuel supply system 62 is configured to be able to supply fuel with a high fuel pressure of 40 MPa or more to the injector 80. The pressure of the fuel supplied to the injector 80 is changed according to the operating state of the engine 1 as will be described later. The fuel supply system 62 is not limited to this configuration.

  Spark plugs 25 and 26 for igniting the air-fuel mixture in the combustion chamber are also attached to the cylinder head 12 (see FIG. 2. Note that the ignition plug is not shown in FIG. 1). The engine 1 includes two spark plugs, a first spark plug 25 and a second spark plug 26, as spark plugs. The two spark plugs 25, 26 are disposed so as to face each other at positions between the intake valve 21 and the exhaust valve 22 provided for each cylinder 18, and are respectively disposed on the central axis of the cylinder 18. The cylinder head 12 is attached so as to extend obliquely downward. In this way, the tip of each spark plug 25, 26 is arranged facing the combustion chamber in the vicinity of the tip of the injector 80 arranged in the center portion of the combustion chamber.

  As shown in FIG. 1, an intake passage 30 is connected to one side of the engine 1 so as to communicate with the intake port 16 of each cylinder 18. On the other hand, an exhaust passage 40 for discharging burned gas (exhaust gas) from the combustion chamber of each cylinder 18 is connected to the other side of the engine 1.

  An air cleaner 31 that filters intake air is disposed at the upstream end of the intake passage 30. A surge tank 33 is disposed near the downstream end of the intake passage 30. The intake passage 30 on the downstream side of the surge tank 33 is an independent passage branched for each cylinder 18, and the downstream end of each independent passage is connected to the intake port 16 of each cylinder 18.

  Between the air cleaner 31 and the surge tank 33 in the intake passage 30, a water-cooled intercooler / warmer 34 that cools or heats the air and a throttle valve 36 that adjusts the amount of intake air to each cylinder 18 are arranged. It is installed. An intercooler bypass passage 35 that bypasses the intercooler / warmer 34 is also connected to the intake passage 30. The intercooler bypass passage 35 is connected to an intercooler for adjusting the flow rate of air passing through the passage 35. A bypass valve 351 is provided. The temperature of fresh air introduced into the cylinder 18 is adjusted by adjusting the ratio between the flow rate of the intercooler bypass passage 35 and the flow rate of the intercooler / warmer 34 through the adjustment of the opening degree of the intercooler bypass valve 351.

  The upstream portion of the exhaust passage 40 is constituted by an exhaust manifold having an independent passage branched for each cylinder 18 and connected to the outer end of the exhaust port 17 and a collecting portion where the independent passages gather. A direct catalyst 41 and an underfoot catalyst 42 are connected downstream of the exhaust manifold in the exhaust passage 40 as exhaust purification devices for purifying harmful components in the exhaust gas. Each of the direct catalyst 41 and the underfoot catalyst 42 includes a cylindrical case and, for example, a three-way catalyst disposed in a flow path in the case.

  A portion between the surge tank 33 and the throttle valve 36 in the intake passage 30 and a portion upstream of the direct catalyst 41 in the exhaust passage 40 are used for returning a part of the exhaust gas to the intake passage 30. They are connected via a passage 50. The EGR passage 50 includes a main passage 51 in which an EGR cooler 52 for cooling the exhaust gas with engine coolant is disposed, and an EGR cooler bypass passage 53 for bypassing the EGR cooler 52. ing. The main passage 51 is provided with an EGR valve 511 for adjusting the amount of exhaust gas recirculated to the intake passage 30, and the EGR cooler bypass passage 53 has a flow rate of exhaust gas flowing through the EGR cooler bypass passage 53. An EGR cooler bypass valve 531 for adjustment is provided.

  The engine 1 configured as described above is controlled by a powertrain control module (hereinafter referred to as PCM) 10. The PCM 10 includes a microprocessor having a CPU, a memory, a counter timer group, an interface, and a path connecting these units. This PCM 10 constitutes a controller.

As shown in FIGS. 1 and 2, detection signals from various sensors SW <b> 1 to SW <b> 16 are input to the PCM 10. The various sensors include the following sensors. That is, on the downstream side of the air cleaner 31, the air flow sensor SW 1 that detects the flow rate of fresh air, the intake air temperature sensor SW 2 that detects the temperature of fresh air, and the downstream side of the intercooler / warmer 34, and the intercooler / warmer 34. A second intake air temperature sensor SW3 for detecting the temperature of fresh air after passing through the EGR gas temperature sensor SW4, which is disposed in the vicinity of the connection portion of the EGR passage 50 with the intake passage 30 and detects the temperature of the external EGR gas. An intake port temperature sensor SW5 that is attached to the intake port 16 and detects the temperature of the intake air just before flowing into the cylinder 18, and an in-cylinder pressure sensor SW6 that is attached to the cylinder head 12 and detects the pressure in the cylinder 18. The exhaust passage 40 is disposed in the vicinity of the connection portion of the EGR passage 50 and has an exhaust temperature and exhaust gas Exhaust temperature sensor SW7 and exhaust pressure sensor SW8 for detecting a force, and is disposed on the upstream side of the direct catalyst 41, the linear O ₂ sensor SW9, direct catalyst 41 and underfoot catalyst 42 for detecting the oxygen concentration in the exhaust gas The lambda O ₂ sensor SW10 that detects the oxygen concentration in the exhaust gas, the water temperature sensor SW11 that detects the temperature of the engine coolant, the crank angle sensor SW12 that detects the rotation angle of the crankshaft 15, and the vehicle An accelerator opening sensor SW13 for detecting an accelerator opening corresponding to an operation amount of an accelerator pedal (not shown), intake side and exhaust side cam angle sensors SW14 and SW15, and a fuel rail 64 of the fuel supply system 62 are attached. And fuel pressure sensor SW16 which detects the fuel pressure supplied to injector 80 It is.

  The PCM 10 performs various calculations based on these detection signals to determine the state of the engine 1 and the vehicle, and accordingly, the injector 80, the first and second spark plugs 25 and 26, and the VVT 72 on the intake valve side. And CVVL 73, exhaust valve side VVL 71 and VVT 74, fuel supply system 62, and various valves (throttle valve 36, intercooler bypass valve 351, EGR valve 511, EGR cooler bypass valve 531) output control signals to actuators To do. Thus, the PCM 10 operates the engine 1.

  FIG. 3 shows an example of the operation region of the engine 1. For the purpose of improving fuel consumption and exhaust emission, the engine 1 is a compression ignition that performs combustion by compression self-ignition without performing ignition by the spark plugs 25 and 26 in a low load region where the engine load is relatively low. Burn. However, as the load on the engine 1 increases, in the compression ignition combustion, the combustion becomes too steep and causes problems such as combustion noise. Therefore, in the engine 1, in a high load region where the engine load is relatively high, the compression ignition combustion is stopped, and the engine 1 is switched to the spark ignition combustion using the spark plugs 25 and 26. As described above, the engine 1 has a CI (Compression Ignition) mode in which compression ignition combustion is performed and an SI (Spark Ignition) mode in which spark ignition combustion is performed in accordance with the operation state of the engine 1, in particular, the load of the engine 1. It is configured to switch. However, the boundary line for mode switching is not limited to the illustrated example.

  In the CI mode, for example, the injector 80 injects fuel into the cylinder 18 at a relatively early timing, for example, during the intake stroke or the compression stroke, so that a relatively homogeneous lean air-fuel mixture (excess air ratio λ ≧ 1) is obtained. For example, λ ≧ 2.5), and the mixture is subjected to compression self-ignition near the compression top dead center. The fuel injection amount is set according to the load of the engine 1.

  In the CI mode, the exhaust valve 22 is opened twice during the intake stroke under the control of the VVL 71, thereby introducing the internal EGR gas into the cylinder 18. The introduction of internal EGR gas increases the compression end temperature and stabilizes compression ignition combustion.

  Since the temperature in the cylinder 18 naturally increases as the engine load increases, the internal EGR amount is reduced from the viewpoint of avoiding premature ignition. For example, the internal EGR amount may be adjusted by adjusting the lift amount of the intake valve 21 under the control of the CVVL 73. Further, the internal EGR amount may be adjusted by adjusting the opening degree of the throttle valve 36.

  For example, in the operation region shown in FIG. 3, in the vicinity of the switching boundary line between the CI mode and the SI mode, the in-cylinder temperature may become too high and it may be difficult to control compression ignition. is there. Therefore, in the high load region in the CI mode operation region, the ratio of the internal EGR introduced into the cylinder 18 is decreased, and instead, the opening degree of the EGR valve 511 is increased and the EGR cooler 52 is cooled. A large amount of external EGR gas may be introduced into the cylinder 18. As a result, the in-cylinder temperature can be kept low, and compression ignition can be controlled.

  On the other hand, in the SI mode, as will be described in detail later, the injector 80 injects fuel into the cylinder 18 from the intake stroke to the initial stage of the expansion stroke, thereby producing a homogeneous or stratified mixture. The mixture is ignited by igniting near the compression top dead center. In the SI mode, the engine 1 is also operated at the theoretical air fuel ratio (λ = 1). This makes it possible to use a three-way catalyst, which is advantageous for improving the emission performance.

  In the SI mode, while the throttle valve 36 is fully opened, the filling amount is adjusted by adjusting the amount of fresh air introduced into the cylinder 18 and the amount of external EGR gas by adjusting the opening of the EGR valve 511. This is effective for reducing pumping loss and cooling loss. In addition, introduction of cooled external EGR gas contributes to avoiding abnormal combustion and also has an advantage of suppressing generation of Raw NOx. In the fully open load range, the external EGR is stopped by closing the EGR valve 511.

  As described above, the geometric compression ratio of the engine 1 is set to 15 or more (for example, 18). Since the high compression ratio increases the compression end temperature and the compression end pressure, the CI mode is advantageous in stabilizing the compression ignition combustion. On the other hand, since the high compression ratio engine 1 is switched to the SI mode in a high load region, there is a disadvantage that abnormal combustion such as pre-ignition and knocking is likely to occur.

  Therefore, in this engine 1, first, the operating state of the engine is a high load low speed region including the maximum load (refer to (1) and (2) in FIG. 3). This corresponds to the low speed range when the area is divided into three, low, medium, and high speed.) When it is in the low speed range, the abnormal combustion is avoided by executing SI combustion with the fuel injection form greatly different from the conventional one. Like to do. Specifically, this fuel injection mode is a period that is significantly retarded from the latter half of the compression stroke to the early stage of the expansion stroke with a fuel pressure that is significantly higher than in the past (hereinafter, this period is referred to as the retard period). The fuel is injected into the cylinder 18 by the injector 80 (see FIG. 4A). This characteristic fuel injection mode is hereinafter referred to as “high pressure retarded injection” or simply “retarded injection”. The high pressure retarded injection shortens the fuel injection period, the mixture formation period, and the combustion period, respectively, and shortens the reaction time of the unburned mixture from the start of fuel injection to the end of combustion. As a result, it is possible to avoid abnormal combustion in a region where the engine load is high and low and abnormal combustion is likely to occur. The fuel pressure may be set to 40 MPa or more. The fuel pressure may be set as appropriate according to the properties of the fuel used, including gasoline, and the upper limit may be about 120 MPa.

  In the high pressure retarded injection, the ignition timing can be advanced in order to avoid abnormal combustion by devising the fuel injection mode. As shown in FIG. 4A, the ignition timing is set in the vicinity of the compression top dead center, and ignition is performed by driving either the first spark plug 25 or the second spark plug 26. Increasing the ignition timing is advantageous for improving thermal efficiency and torque. In addition, the injection timing and ignition timing shown to Fig.4 (a) are illustrations, and are not limited to this.

  In the operation region where the high pressure retarded injection is performed, in the region (see (2) in FIG. 3) on the lower load side than the maximum load region (see (1) in FIG. 3), the occurrence of abnormal combustion is the above ( Therefore, the upper limit of the fuel pressure may be lowered (for example, about 80 MPa), and the fuel injection timing may be advanced within the later stage of the compression stroke.

  Note that, in the high load region in the CI mode operation region where compression ignition is likely to be difficult, as described above, in addition to reducing the introduction ratio of the internal EGR, the high load side SI mode High pressure retarded injection may be performed as in the operation region (see (2) in FIG. 2). By doing so, since a sharp rise in the combustion pressure in the CI mode is suppressed, an increase in engine noise can be suppressed.

  On the other hand, the operating state of the engine is a high-speed region where the load is high (see (3) in FIG. 3). Note that the “high-speed region” here is when the operating region of the engine 1 is divided into three regions: low, medium and high 4), the fuel is injected within the intake stroke period in which the intake valve 21 is open, not in the retard period, as shown in FIG. 4 (b). . Hereinafter, this fuel injection mode is referred to as “intake stroke injection”. In the intake stroke injection, a high fuel pressure is not required, so the fuel pressure is lowered (for example, less than 40 MPa) as compared with the high pressure retarded injection. As a result, the mechanical resistance loss of the engine 1 due to the driving of the high-pressure fuel pump 90 is reduced, which is advantageous in improving fuel consumption.

  The high pressure retarded injection shortens the reaction time of the unburned mixture by performing the fuel injection within the retard period. However, the reduction of the reaction time is performed in the low speed range where the rotational speed of the engine 1 is relatively low. This is effective because the real time with respect to the change in the crank angle is long, whereas it is not so effective in the high speed range where the rotational speed of the engine 1 is relatively high because the real time with respect to the change in the crank angle is short. Conversely, in retard injection, since the fuel injection timing is set near the compression top dead center, air that does not contain fuel, that is, has a high specific heat ratio, is compressed in the compression stroke. As a result, in the high speed range, the temperature in the cylinder 18 at the compression top dead center (that is, the compression end temperature) becomes high, and this high compression end temperature causes knocking. Therefore, when performing retarded injection at high speed, the ignition timing must be retarded to avoid knocking.

  Therefore, in the engine 1, in the region (3), which is a high-load high-speed region, intake stroke injection is performed instead of retard injection.

  In the intake stroke injection, it is possible to lower the specific heat ratio of the in-cylinder gas (that is, the air-fuel mixture containing fuel) during the compression stroke, thereby keeping the compression end temperature low. Since the compression end temperature is lowered in this manner, knocking can be suppressed, so that the ignition timing can be advanced. Therefore, in the region (3), ignition is performed in the vicinity of the compression top dead center, as in the high pressure retarded injection. However, in the region (3), from the viewpoint of shortening the combustion period, the ignition is a two-point ignition that drives both the first and second spark plugs 25 and 26. The first and second spark plugs 25 and 26 may be ignited simultaneously. The first and second spark plugs 25 and 26 may be driven with a time difference.

  Therefore, in this engine 1, in the regions (1) and (2) shown in FIG. 3, that is, in the low rotation region with a high load, the thermal efficiency is improved while avoiding abnormal combustion by using high pressure retarded injection.

  Further, in this engine, in the high-load high-rotation region (region (3) shown in FIG. 3), the intake stroke injection is performed to improve the thermal efficiency while avoiding abnormal combustion. Further, in the high-load high-rotation range, by performing two-point ignition, a flame spreads from each of a plurality of fire types in the combustion chamber, so that the flame spreads quickly and the combustion period is shortened. In the two-point ignition, even if the ignition timing is after the compression top dead center, the position of the center of gravity of the combustion is positioned as advanced as possible, which is advantageous for improving the thermal efficiency and torque, and hence for improving the fuel consumption. The number of spark plugs is not limited to two. The number of spark plugs may be three or more, or one. Multipoint ignition may be performed during high-pressure retarded injection. The high pressure retarded injection may be divided as required, and similarly, the intake stroke injection may also be divided as required. As a result, at least one injection is performed in the intake stroke, and fuel injection may be performed in the compression stroke.

(Basic injector configuration)
FIG. 5 shows the configuration of the injector 80. The injector 80 directly attracts and strokes the needle 83 disposed in the fuel passage by a magnetic circuit formed by energizing the solenoid coil. Thus, a plurality of nozzle holes 84 (see also FIG. 11) formed in the distal end surface 804 are configured to be solenoid driven. In particular, the injector 80 has two solenoid coils, a first solenoid coil 81 and a second solenoid coil 82, and the stroke amount of the needle 83 is set to a first stroke amount S1 which is a relatively small stroke amount. And a second stroke amount S2 that is a relatively large stroke amount. Accordingly, as illustrated in FIG. 6, high fuel injection accuracy is ensured from a small injection amount to a large injection amount. As described above, such an injector 80 has a large injection when the operation state of the engine 1 is in the high load region from the small injection amount when the operation state of the engine 1 is in the low load region and the compression ignition combustion is performed. It is suitable for the engine 1 that requires high fuel injection accuracy over a wide range up to the amount. In particular, the engine 1 uses gasoline-containing fuel, and variations in fuel injection amount are highly sensitive to deterioration in exhaust emissions, and variations in fuel injection amount are also highly sensitive to deterioration in combustion stability. In particular, high fuel injection accuracy is required.

  The main body of the injector 80 includes a large-diameter cylindrical first valve body 841 and a small-diameter cylindrical second valve body 842 extending from one end of the first valve body 841 and closed at a coupling member 843. Concatenated.

  A cylindrical case 85 is accommodated in the first valve body 841, and a fuel passage 800 is defined by an inner peripheral surface of the case 85. The case 85 has an upper end opened at the base end (the upper end in FIG. 5) of the injector 80, and a lower end opened to communicate with the base end opening of the second valve body 842. Thus, a fuel passage 800 for supplying fuel from the fuel inlet 844 communicating with the fuel rail 64 at the base end of the injector 80 to each nozzle hole 84 opened at the tip of the injector 80 is formed inside the injector 80. Will be.

  As will be described later, the cylindrical case 85 is basically made of a magnetic material so as to constitute a part of the magnetic circuit when the first and second solenoid coils 81 and 82 are energized. Specifically, the case 85 is made of, for example, a ferritic metal such as ferritic steel.

  A needle 83 that opens and closes each nozzle hole 84 is disposed in the case 85 so as to be coaxial with the case 85. The needle 83 extends from the vicinity of the central portion in the axial direction of the case 85 toward the tip of the injector 80, and the tip thereof is located at the tip of the second valve body 842. The needle 83 is formed with a hole 831 that opens to the base end surface thereof and extends toward the distal end portion along the central axis. The hole 831 is near the central portion of the needle 83 in the axial direction. Open to the peripheral surface. The hole 831 functions as a part of a fuel passage that connects an upper side of a second movable core 872 described later and a lower side of the first movable core 871.

  The first solenoid coil 81 and the second solenoid coil 82 are respectively disposed between the first valve body 841 and the case 85 so that the first solenoid coil 81 is on the lower side and the second solenoid coil 82 is on the upper side. Are arranged at predetermined intervals in the axial direction.

  In the case 85, a cylindrical first fixed core 861 is fixed at a position facing the first solenoid coil 81 across the case 85, and at a position facing the second solenoid coil 82, Similarly, a cylindrical second fixed core 862 is fixed. These first and second fixed cores 861 and 862 are made of a magnetic material, and individually form part of the magnetic circuit when the first and second solenoid coils 81 and 82 are energized.

  A ring-shaped first movable core 871 is extrapolated to the needle 83 by providing a gap S1 having a predetermined size with respect to the lower end surface of the first fixed core 861 below the first fixed core 861. On the other hand, on the lower side of the second fixed core 862, a gap S2 having a predetermined size is provided with respect to the lower end surface of the second fixed core 862, so that the link-shaped second movable core 872 is provided. Is arranged in a state of being extrapolated to the needle 83. The gap S1 and the gap S2 are set so that S1 <S2.

  The first movable core 871 extrapolated to the needle 83 is engaged with a step portion formed at the center of the needle 83, while the second movable core is also extrapolated to the needle 83. 872 is engaged with a step formed at the upper end of the needle 83. Each of the first and second movable cores 871 and 872 is disposed so as to be capable of reciprocating in the axial direction in the case 85. When the first movable core 871 moves upward, the first movable core 871 and the stepped portion are arranged. The needle 83 moves upward by the engagement. Also, when the second movable core 872 moves upward, the needle 83 moves upward due to the engagement between the second movable core 872 and the stepped portion. Therefore, the needle 83 can be stroked by selectively moving the first movable core 871 and the second movable core 872.

  The needle 83 is biased downward by a spring 881 disposed on the base end side thereof, and is configured to close each injection port 84 in a normal state. On the other hand, the first and second movable cores 871 and 872 are urged upward by springs 882 and 883, respectively, whereby the first and second movable cores 871 and 872 are normally attached to the needle 83. It is comprised so that the state engaged with each step part may be maintained.

  The first and second movable cores 871 and 872 are each made of a magnetic material, and when energized to the first solenoid coil 81 as shown in an enlarged view in FIG. 7, the first valve body 841 and the case 85 are energized. , A magnetic circuit (see a thick solid arrow in the figure) that passes through the first movable core 871 and the first fixed core 861 (and a first type of reinforcing member 891 described later) is formed. The first movable core 871 that can reciprocate in the axial direction is sucked upward. As the first movable core 871 is sucked, the needle 83 engaged with the first movable core 871 at the step portion also acts on the needle 83 due to the urging force of the spring 881 (and fuel pressure as described later). Move upward against back pressure). Each of the first movable core 871 and the needle 83 moves upward until the first movable core 871 comes into contact with the first fixed core 861. That is, the needle 83 strokes by the first stroke amount S1 corresponding to the gap S1.

  Similarly, when the second solenoid coil 82 is energized, the detailed illustration is omitted, but the first valve body 841, the case 85, the second movable core 872, and the second fixed core 862 (and the first type described later). The magnetic circuit passing through the reinforcing member 891) is formed, so that the second movable core 872 is attracted upward. As the second movable core 872 is sucked, the needle 83 engaged with the second movable core 872 at the step portion moves upward against the biasing force of the spring 881 (and the back pressure acting on the needle 83). To do. Each of the second movable core 872 and the needle 83 strokes by the second stroke amount S2 corresponding to the gap S2 until the second movable core 872 contacts the second fixed core 862.

  Here, in the case 85, a total of two locations, a location corresponding to between the first fixed core 861 and the first movable core 871 and a location corresponding to between the second fixed core 862 and the second movable core 872. Each includes a non-magnetic portion 851 for preventing a shortcut of the magnetic circuit. Such a non-magnetic part 851 may be provided in the middle part of the cylindrical case 85 extending in the axial direction by joining the case divided into a plurality of parts by friction joining. Friction coupling enables the case 85 and the non-magnetic portion 851 to be firmly coupled without reducing the thickness, and as will be described later, the strength of the case 85 that receives internal pressure due to high fuel pressure is increased. It is advantageous to increase.

(Reinforcement structure that enables high fuel pressure in the injector)
As described above, the fuel pressure may be set to a high fuel pressure of 40 MPa or more, for example, about 120 MPa at the maximum, thereby increasing the internal pressure of the case 85. To counter this high internal pressure, the thickness of the case 85 must be increased. However, since the case 85 constitutes a part of the magnetic circuit, as described above, the case 85 is made of, for example, a ferrite metal and has a relatively low strength. Therefore, if the case 85 tries to cope with a high internal pressure alone, the thickness of the case 85 will be significantly increased. In such a thick case 85, it is no longer possible to configure a magnetic circuit that straddles the inside and outside of the case 85.

  Therefore, in this injector 80, the case 85 that partitions the fuel passage 800 is configured to have a substantially double-pipe structure by fitting a reinforcing member to the case 85 from the outside. Specifically, the injector 80 includes a first type of reinforcing member 891 disposed adjacent to the first and second solenoid coils 81 and 82 in the axial direction as reinforcing members, and first and second solenoid coils. For each of 81 and 82, a second-type reinforcing member 892 interposed between the case 85 and the case 85 is provided.

  In the injector 80 of the illustrated example, the first type of reinforcing member 891 is located at a position between the first solenoid coil 81 and the second solenoid coil 82 and at a position below the first solenoid coil 81. The first valve body 841 and the case 85 are disposed. The first type of reinforcing member 891 adjacent in the axial direction to the first or second solenoid coil 81 or 82 is configured to constitute a part of the magnetic circuit when the solenoid coil is energized, as shown in an enlarged view in FIG. Further, it is made of a magnetic material. From the viewpoint of increasing the efficiency of the magnetic circuit, the magnetic body constituting the first type of reinforcing member 891 may be made of a ferritic metal such as ferritic steel, like the case 85 described above. The first type of reinforcing member 891 is attached to the case 85 so as to be externally fitted, whereby a load in the direction from the radially outer side to the inner side acts on the case 85. This load opposes the internal pressure caused by the fuel pressure acting on the inner peripheral surface of the case 85 in the direction from the inner side to the outer side in the radial direction. The first type of reinforcing member 891 may be attached so as to be externally fitted to the case 85 by employing an appropriate method such as press fitting or shrink fitting.

  On the other hand, the second-type reinforcing member 892 is interposed between the first solenoid coil 81 and the case 85 and between the second solenoid coil 82 and the case 85 as described above. The axial length of the second type reinforcing member 892 corresponds to the axial lengths of the first solenoid coil 81 and the second solenoid coil 82. Unlike the first-type reinforcing member 891, the second-type reinforcing member 892 is made of a non-magnetic material so that the magnetic circuit does not shortcut when the first or second solenoid coil 81, 82 is energized. The nonmagnetic material constituting the second type reinforcing member 892 may be made of, for example, austenitic steel. Similarly to the first type of reinforcing member 891, the second type of reinforcing member 892 is also attached so as to be externally fitted to the case 85, so that the case 85 can be fitted from the radially outer side to the inner side. A load that opposes the internal pressure acts in the direction toward. The second type reinforcing member 892 may also be attached so as to be externally fitted to the case 85 by employing an appropriate method such as press fitting or shrink fitting.

  In this way, by attaching the first-type reinforcing member 891 and the second-type reinforcing member 892 to the case 85 so as to be externally fitted, a high internal pressure due to the high fuel pressure in the fuel passage 800 is obtained. In the case 85 on which a countercurrent acts, a counter force from the outside in the radial direction to the inside acts. In addition, the double tube structure of the case and the reinforcing member makes it possible to distribute stress to the two tubes, the inner side and the outer side, as shown in FIG. As a result, the required strength can be ensured without increasing the thickness of the case 85. This is advantageous when the magnetic circuit is formed so as to straddle the inside and outside of the case 85.

  The first-type reinforcing member 891 is disposed adjacent to the first or second solenoid coils 81 and 82 in the cylinder axis direction, and includes a magnetic body that constitutes a part of the magnetic circuit. This contributes to both high fuel pressure by reinforcing the case 85 and the formation of a magnetic circuit. This first type of reinforcing member 891 is made of ferritic steel having high magnetic permeability and low residual magnetism, which is advantageous for improving the performance of the injector 80.

  On the other hand, the second-type reinforcing member 892 is interposed between the first or second solenoid coils 81 and 82 and the case 85, and includes a non-magnetic material, thereby providing a shortcut for the magnetic circuit. This contributes to both high fuel pressure by reinforcing the case 85 and the formation of a magnetic circuit. Constructing the second type reinforcing member 892 of austenitic steel enables the second type reinforcing member 892 to be thin due to its high strength, and the first and second solenoid coils 81 and 82 and the case 85 By narrowing the interval, it is advantageous for forming a highly efficient magnetic circuit and also for reducing the diameter of the injector 80.

(Support structure of first and second movable cores)
Here, in the injector 80 shown in FIG. 5, the springs 882 and 883 are disposed below the first movable core 871 and the second movable core 871, thereby causing the first and second movable cores 871 and 872 to face upward, respectively. I am trying to be energized. In such a support configuration, as shown in FIG. 8A, when the second solenoid coil 82 is energized, the second movable core 872 has a predetermined stroke as shown by a solid line in FIG. The first movable core 871 is disengaged from the stepped portion of the needle 83 as the needle 83 is moved by the amount S2 and the needle 83 is stroked upward accordingly. The core 871 moves upward by the biasing force of the spring 882.

  Thereafter, the energization of the second solenoid coil 82 is terminated, and the second movable core 872 and the needle 83 are both lowered according to the difference between the downward biasing force of the spring 881 and the upward biasing force of the spring 883. Then, the stepped portion of the needle 83 and the first movable core 871 come into engagement again (see “contact” in FIG. 5A), and thereafter the upward biasing force of the spring 882 is applied, and the spring 881 In accordance with the difference between the downward biasing force and the upward biasing force of the spring 882 and the spring 883, the first and second movable cores 871, 872 and the needle 83 are integrally lowered. In other words, the lowering speed of the needle 83 is lowered in the middle, and the impact when the distal end portion of the needle 83 is seated on a seat portion 801 described later is softened. This is advantageous for suppressing collision noise.

  On the other hand, when the first solenoid coil 81 is energized, as the first movable core 871 moves as shown by the broken line in FIG. 8B, the needle 83 and the second movable core as shown by the solid line in the figure. Each of 872 strokes upward by a predetermined stroke amount S1.

  When the energization of the first solenoid coil 81 is finished, the first and second movable cores 871 and 872 and the needle 83 are selected according to the difference between the downward biasing force of the spring 881 and the upward biasing force of the spring 882 and the spring 883. Are lowered as a whole, and in this case, the lowering speed is relatively small. Therefore, similarly to the above, the impact when the tip of the needle 83 is seated on the seat 801 is reduced, which is advantageous for suppressing the collision noise.

  FIG. 9 shows a modification in which a downward urging force is applied to the first movable core 871 by disposing a spring 882 on the upper side of the first movable core 871. In FIG. 9, the same components as those of the injector 80 shown in FIG. In the injector 80 shown in FIG. 9, a spacer 884 is disposed below the first movable core 871, thereby defining a gap S <b> 1 between the first movable core 871 and the first fixed core 861. .

  In the injector 80 as shown in FIG. 9, when the second solenoid coil 82 is energized as described above, as shown by the solid line in FIG. Although it moves upward by the stroke amount S2, the first movable core 871 is biased downward, so that it remains stopped without moving as shown by the broken line in FIG.

  When energization of the second solenoid coil 82 is completed, both the second movable core 872 and the needle 83 are lowered according to the difference between the downward biasing force of the spring 881 and the upward biasing force of the spring 883. As described above, since the first movable core 871 does not move upward, the first movable core 871 engages with the step portion of the needle 83 during the lowering, unlike FIG. 8A. There is no. As a result, the needle 83 is seated on the seat portion 801 without the lowering speed of the needle 83 changing midway.

  On the other hand, when the first solenoid coil 81 is energized, as the first movable core 871 moves as shown by the broken line in FIG. 10B, the needle 83 and the second movable core as shown by the solid line in the drawing. 872 also strokes upward by a predetermined stroke amount S1. At this time, since the downward urging force by the spring 882 acts on the first movable core 871, the ascending speed of the needle 83 and the like is smaller than that in FIG. 8B. When the energization of the first solenoid coil 81 is finished, the first and second movable cores 871 and 872 and the needle 83 are changed according to the difference between the downward biasing force of the spring 881 and the spring 882 and the upward biasing force of the spring 883. Is lowered integrally, so that the lowering speed is larger than in the example of FIG.

  Although not shown in the drawings, in each of the examples of FIGS. 5 and 9, a spring 883 is disposed on the upper side of the second movable core 872 so as to apply a downward biasing force to the second movable core 872. It may be configured.

  In the injector 80 shown in FIGS. 5 and 9, a solenoid coil having a relatively large stroke amount, that is, a second solenoid coil 82 is arranged on the upper side, and a solenoid coil having a relatively small stroke amount, that is, a first solenoid. Although the coil 81 is arranged on the lower side, it is arranged opposite to the above so that the solenoid coil having a relatively large stroke amount is on the lower side and the solenoid coil having a relatively small stroke amount is on the upper side. Also good.

(Structure to reduce the suction force that increases as the fuel pressure of the injector increases)
In the injector 80 having a structure in which a needle is disposed in the fuel passage 800, a back pressure caused by the fuel pressure acts on the needle 83 in a valve-closed state. That is, a load acting in the valve closing direction acts on the needle 83. The back pressure is proportional to the magnitude of the fuel pressure. When the fuel pressure is set high as in the injector 80 disclosed herein, the back pressure acting on the needle 83 also becomes high. The back pressure is related to the suction force of the solenoid coils 81 and 82 when the needle 83 is opened. The higher the back pressure, the greater the required suction force. Therefore, in the injector 80, the diameter of the seat portion 801 on which the tip of the needle 83 is seated is reduced so that the suction force required for opening the needle 83 is reduced.

  FIG. 11 shows the configuration of the tip of the injector 80 in an enlarged manner. The tip portion of the needle 83 is formed to be tapered, and the seat portion 801 is configured such that the middle portion of the tapered tip portion of the needle 83 is seated and separated as shown by a two-dot chain line in FIG. It is configured to sit down. Accordingly, the diameter φ1 of the seat portion 801 is smaller than the diameter φ2 of the basic cylindrical portion at the tip of the needle 83. In the state where the needle 83 is seated on the seat portion 801, the back pressure acting on the needle 83 due to the fuel pressure is proportional to the diameter of the seat portion 801. Is set small and the area is reduced, the back pressure acting on the needle 83 can be reduced accordingly. In the state where the needle 83 is seated on the seat portion 801, the fuel pressure acts on a surface inclined with respect to the axial direction at the tip of the needle 83, and this fuel pressure acts in the axial direction (valve opening direction) of the needle 83. Although the force to be applied becomes a cos (cosine) component, the pressure receiving area is increased by the inclination, so that the force acting in the axial direction of the needle 83 is offset by the cos component.

  The reduction of the back pressure acting on the needle 83 reduces the suction force necessary for opening the valve. This is advantageous in reducing the size of the first and second solenoid coils 81 and 82. The downsizing of the first and second solenoid coils 81 and 82 enables the diameter of the injector 80 to be reduced, so that the cylinder head 12 of the engine 1 extends along the axis of the cylinder 18 as shown in FIG. This is advantageous in securing a mounting space for the injector 80 to be mounted. The reduction of the suction force is also advantageous for saving power consumption. In addition, since the tip of the needle 83 is tapered, when the needle 83 is separated, the fuel flowing through the seat portion 801 is guided by the inclined surface of the tip of the needle 83, and the flow resistance decreases. The fuel pressure on the throttle portion 802 side is likely to increase. This increases the force acting on the needle 83 in the valve opening direction, which is advantageous in reducing the suction force required for valve opening.

  An aperture 802 is provided so as to be continuous with the sheet portion 801 having a reduced diameter. The aperture portion 802 is configured to have a smaller diameter than the diameter of the sheet portion 801. Further, an enlarged portion 803 having an enlarged diameter is provided continuously to the aperture portion 802. The portion from the throttle portion 802 to the enlarged portion 803 is configured so that the inner wall has a smooth curved surface, and thereby the flow of fuel from the seat portion 801 to the enlarged portion 803 via the throttle portion 802 is made. It is smooth. Then, a plurality of, in the illustrated example, ten nozzle holes 84 communicate with the enlarged portion 803, and the ten nozzle holes 84 have a high fuel pressure as shown in FIG. Are arranged on the tip end surface 804 of the injector 80 which is recessed in a spherical shape so as to be opposed to each other, at an equal interval and circumferentially.

  In this way, by connecting the ten nozzle holes 84 to the enlarged portion 803 having an enlarged diameter, it is possible to ensure a sufficient interval between the nozzle holes 84 on the distal end surface 804 of the injector 80. As a result, atomization of the fuel injected through each nozzle hole 84 at a high fuel pressure is improved. Good atomization of the injected fuel is advantageous for the formation of a homogeneous lean air-fuel mixture, particularly in a low-load region where compression ignition combustion is performed, and compression ignition combustion can be stabilized.

  In addition, the arrangement of the nozzle holes is not limited to the circumferential arrangement as shown in FIG. 11B, and for example, as shown in FIG. 12, a plurality of (see FIG. 12) so as to form a double circle inside and outside in the radial direction. In the example, ten nozzle holes 84 may be arranged. Moreover, what is necessary is just to set the number of nozzle holes to an appropriate number.

(Correspondence between the drive of the two-stage solenoid injector and the operating range of the engine)
In the injector 80 having this configuration, as described above, when the first solenoid coil 81 is energized, the needle 83 can be stroked by the first stroke amount S1, and when the second solenoid coil 82 is energized. The needle 83 can be stroked by the second stroke amount S2. Here, the first stroke amount S1 and the second stroke amount S2 are set so as to satisfy S1 <S2, so that the injector 80 strokes the needle 83 with different stroke amounts to inject fuel. It is possible to make it.

  As shown in FIG. 2, the PCM 10 outputs a control current to the first solenoid coil 81 and / or the second solenoid coil 82 of the injector 80 so that the injection amount required according to the operating state of the engine 1 is obtained. Thereby, a required amount of fuel is injected into the cylinder 18. That is, when the required injection amount is small, the first solenoid coil 81 is energized in the CI mode in which compression ignition combustion is performed specifically in the operation region shown in FIG. As a result, the needle 83 is opened via the first movable core 871, and after the needle 83 is maintained at the stroke amount S1 (that is, a small stroke), energization is terminated. Then, the needle 83 is closed. As a result, as shown in FIG. 6, the waveform of the instantaneous injection rate with respect to time has a predetermined trapezoidal shape, thereby improving the injection accuracy with a relatively small injection amount. In the CI mode, fuel injection is performed within the intake stroke period to form a homogeneous lean air-fuel mixture, so that even if there is some variation in the fuel injection amount, the stability of compression ignition combustion is sufficiently ensured. The

  On the other hand, when the required injection amount is large, specifically, in the SI mode in which spark ignition combustion is performed in the operation region shown in FIG. 3, at least the second solenoid coil 82 is energized and the needle 83 is moved via the second movable core 872. Open the valve. Then, after maintaining the needle 83 with the stroke amount S2 (large stroke), the energization is terminated and the needle 83 is closed. Thereby, as shown in FIG. 6, the waveform of the predetermined instantaneous injection rate with respect to time is made to be a trapezoidal shape similar to the waveform at the time of a small stroke, and thereby, the injection accuracy at a relatively large injection amount Can also be increased. In particular, in the operation region shown in FIG. 3, in the regions (1) and (2), a high injection rate is required because high pressure retarded injection is performed, but at a high fuel pressure and a relatively large second stroke amount S2. This is achieved by stroking the needle 83, and a required amount of fuel can be injected into the cylinder 18 near the compression top dead center in a short time with high fuel pressure.

  Here, when the needle 83 is stroked by the second stroke amount S2, only the second solenoid coil 82 may be energized. Further, both the first solenoid coil 81 and the second solenoid coil 82 may be energized. When energizing both the first and second solenoid coils 81, 82, it is preferable to energize the first solenoid coil 81 at least at the start of the valve opening operation of the needle 83. In other words, at the start of the valve opening operation of the needle 83, it is necessary to generate a back pressure that acts on the needle 83 due to the fuel pressure and a suction force that opposes the urging force of the spring 881. The gap S1 between the corresponding first movable core 871 and the first fixed core 861 is smaller than the gap S2 between the second movable core 872 and the second fixed core 862 corresponding to the second solenoid coil 82. The current value required for generation becomes low. In addition, after the needle 83 is separated from the seat portion 801, the back pressure due to the fuel pressure disappears, and therefore the suction force required for the stroke of the needle 83 is reduced accordingly. Accordingly, a small amount of current is supplied to the second solenoid coil 82. That is, when the needle 83 is stroked by the second stroke amount S2, energizing the first solenoid coil 81 at the start of the valve opening operation of the needle 83 makes it possible to suppress the total power consumption. The second solenoid coil 82 may be energized after a predetermined time after the energization of the first solenoid coil 81, or the energization of the first solenoid coil 81 and the second solenoid coil 82 may be energized. You may start electricity supply.

  As described above, the first and second types of solenoid coils 81 and 82 are provided, and thereby the stroke amount of the needle 83 can be changed to the first stroke amount S1 and the second stroke amount S2. By using the injector 80, in the low load region where the injection amount is relatively small, it is possible to accurately inject a small injection amount by driving only the first solenoid coil 81, and the compression ignition combustion can be performed. Stability is ensured. On the other hand, in a high load region where the injection amount is relatively large, particularly a region where high pressure retarded injection is performed, at least the second solenoid coil 82 is driven to achieve a high injection rate in combination with high fuel pressure. An amount of fuel can be injected into the cylinder near the compression top dead center in a short period of time with high fuel pressure, which is advantageous for avoiding abnormal combustion. In this way, it is possible to improve fuel efficiency over a wide operating range of the engine 1.

(Configuration of high-pressure fuel pump)
13 to 15 show the configuration of the high-pressure fuel pump 90. As described above, in this engine 1, fuel containing gasoline is injected at a high fuel pressure of 40 MPa or more and a maximum of about 120 MPa. For this reason, the high-pressure fuel pump 90 is a conventional plunger type. It has a different configuration from the fuel pump.

  That is, as shown in FIGS. 14A to 14C, the high-pressure fuel pump 90 includes a cylinder 91 arranged to extend in the vertical direction, a plunger 94 inserted in the cylinder 91, and a plunger 94. A drive mechanism 93 that causes a stroke in the vertical direction within the cylinder 91 is provided.

  As shown also in FIG. 15, the cylinder 91 is formed in the first casing 901, and an inlet 911 for allowing fuel to flow into the cylinder 91 is provided at the upper end of the cylinder 91. Although not shown in detail in the first casing 901, a supply chamber 912 in which the fuel sent from the fuel tank is stored is formed (see the thick solid arrow in FIG. 14). An inflow port 911 formed at the upper end of the cylinder 91 communicates with the supply chamber 912. The supply chamber 912 has a diameter that is the same as or larger than the diameter of the cylinder 91, and is configured to gradually shrink toward the inflow port 911.

  A suction valve 92 is attached to the inflow port 911, and the suction valve 92 opens the inflow port 911, whereby fuel flows into the cylinder 91 from the supply chamber 912. The suction valve 92 includes a valve body 921 that is biased upward so as to be seated on the inlet 911. The valve body 921 normally closes the inlet 911. When 921 is pushed downward, the inlet 911 is opened to allow fuel to flow into the cylinder 91 from the inlet 911 (see FIG. 15).

  The suction valve 92 also has a rod 922 arranged so as to extend in the vertical direction above the valve body 921. The lower end of the rod 922 is in contact with the upper end surface of the valve body 921, while the upper end thereof is Passes through the supply chamber 912 and reaches the upper side thereof. The rod 922 is configured to reciprocate in the vertical direction by a solenoid coil 923 attached to the upper side of the first casing 901. In other words, when the solenoid coil 923 is energized via the coupler 924 provided at the upper end of the high-pressure fuel pump 90, the rod 922 moves downward to push down the valve body 921 biased upward, thereby Then, the valve body 921 is separated from the inlet 911 and the inlet 911 is opened. Thus, the fuel flows into the cylinder 91. On the other hand, when energization of the solenoid coil 923 is stopped, the valve body 921 is lifted by the upward biasing force, whereby the valve body 921 is seated on the inlet 911 and the inlet 911 is closed. Thus, the suction valve 92 is configured as an electromagnetic valve that is controlled to open and close by the PCM 10.

  As shown in FIGS. 14A and 14B, the discharge port 913 for discharging high-pressure fuel from the cylinder 91 is provided on the side near the upper end of the cylinder 91. Reference numeral 914 denotes a pulsation damper 914 that is disposed on the inflow side of the high-pressure fuel pump 90 and suppresses pulsation associated with fuel injection of the injector 80.

  The plunger 94 is inserted into the cylinder 91 as described above, and strokes in the vertical direction by a drive mechanism 93 described later. When the plunger 94 descends from the top dead center state shown in FIG. 14A, the fuel in the supply chamber 912 flows into the cylinder 91 through the inflow port 911 opened in accordance with the timing, In the state where the inflow port 911 is closed, the plunger 94 rises from the bottom dead center state shown in FIG. 14B, so that the pressure of the fuel in the cylinder 91 increases and the pressurized fuel is discharged from the discharge port 913. Then, the fuel is discharged from the high-pressure fuel pump 90 toward the fuel rail 64.

  The drive mechanism 93 includes a piston 931 that is fixed to the lower end of the plunger 94 and capable of reciprocating in the vertical direction, a spring 932 that biases the piston 931 downward, and a roller that is attached to the piston 931. 933, and a cam 934 that strokes the plunger 94 in the vertical direction via the roller 933 and the piston 931.

  The piston 931 is inserted into a piston housing portion 903 having a circular cross section formed in a second casing 902 attached to the lower side of the first casing 901 so as to reciprocate in the piston housing portion 903 in the vertical direction. It is configured.

  Although detailed illustration is omitted, the roller 933 is a piston so as to be rotatable with respect to an axis orthogonal to the stroke direction of the plunger 94 (that is, the vertical direction in the drawing in FIG. 14) via a rolling bearing or a sliding bearing. It is attached to 931 (see FIG. 14C). The roller 933 reduces the frictional resistance with the cam 934, which is advantageous for reducing the driving torque of the high-pressure fuel pump 90, and hence for reducing the mechanical resistance loss of the engine 1.

  A cam housing portion 904 is formed in the second casing 902 so as to be continuous with the lower end of the piston housing portion 903, and the cam 934 is supported by the cam shaft 935 in the cam housing portion 904. Thus, the plunger 94 is disposed so as to be rotatable with respect to an axis orthogonal to the stroke direction. As shown in FIGS. 14A and 14B, the cam 934 is configured as a two-ridge cam, and the peaks (cam nose) are provided on both sides of the rotation center axis. The camshaft 935 is drivingly connected to the crankshaft 15 of the engine 1 through a sprocket 936 fixed to the tip thereof and a chain 937 wound around the sprocket 936, as conceptually shown in FIG. . The cam shaft 935 of the drive mechanism 93 is configured to rotate with respect to the crankshaft 15 of the engine 1 at a reduction ratio of 1: 1.

  Here, since the drive mechanism 93 of the high-pressure fuel pump 90 is drivingly connected to the crankshaft 15, as shown in FIG. 13, the camshafts 210 and 220 of the engine 1 are closer to the crankshaft 15 than the camshafts 210 and 220. Will be placed. In addition, as described above, the high-pressure fuel pump 90 is provided with the inlet 911 at the upper end of the cylinder 91 extending in the vertical direction, and the inlet is communicated with the supply chamber 912 provided above the cylinder 91. A solenoid coil 923 for driving the suction valve 92 is disposed further above the chamber 912. Thus, although the overall height of the high-pressure fuel pump 90 is set to be relatively high, as described above, disposing the bulky high-pressure fuel pump 90 at a relatively low height position on the side of the engine 1 The high-pressure fuel pump 90 can be disposed without exceeding the overall height of the engine 1, which is advantageous for layout in the engine room.

  In the high-pressure fuel pump 90 having the above-described configuration, in order to achieve a high fuel pressure of 40 MPa or more, the volume of the cylinder 91 when the plunger 94 is at the top dead center is set to be significantly small. That is, if the fuel pressure increases, the compressibility of the fuel cannot be ignored. Therefore, by reducing the cylinder volume at the top dead center, both the high fuel pressure and the discharge flow rate can be ensured.

  However, by reducing the cylinder volume at the top dead center, when the plunger 94 is lowered and fuel is caused to flow into the cylinder 91, the pressure drop in the cylinder 91 increases. This causes cavitation in the vicinity of the inflow port 911 in the case of gasoline-containing fuel, which may make it difficult for the fuel to flow into the cylinder 91.

  Therefore, in the high-pressure fuel pump 90 having the above-described configuration, when the intake valve 92 is opened by providing the supply chamber 912 having a relatively large volume above the cylinder 91 via the inflow port 911, an arrow is shown in FIG. As described above, the fuel flows from the supply chamber 912 in the axial direction of the cylinder 91, in other words, in the stroke direction of the plunger 94, and flows into the cylinder 91 through the inflow port 911. Such a configuration smoothes the fuel flow into the cylinder 91 and suppresses the occurrence of cavitation due to the pressure drop when the plunger 94 is lowered. Here, since the supply chamber 912 is formed so as to be gradually reduced in the fuel flow direction, the inflow of fuel can be made smoother. As a result, the fuel can surely flow into the cylinder 91, and in the high-pressure fuel pump 90, a high fuel pressure of 40 MPa or more and securing of a necessary fuel discharge amount are compatible.

  In such a high-pressure fuel pump 90 with a high fuel pressure, the load acting on the drive mechanism 93 is increased by the reaction force when the plunger 94 reaches top dead center. For this reason, if it is going to counter this big load, there exists a possibility that the drive mechanism 93 may enlarge. In particular, if the roller 933 of the drive mechanism 93 is to be supported by the piston 931 via the rolling bearing, the roller and the rolling bearing are greatly increased in size. Therefore, in the high-pressure fuel pump 90 having the above-described configuration, the load acting on the drive mechanism 93 is reduced by reducing the cylinder diameter and the plunger diameter. On the other hand, in order to achieve a high fuel pressure, the stroke amount of the plunger 94 is set relatively large (see FIGS. 14A and 14B). As a result, the high-pressure fuel pump 90 is configured to have a long stroke in which the stroke amount of the plunger 94 is larger than the cylinder diameter. This balances downsizing the high-pressure fuel pump 90 and increasing the fuel pressure.

  In addition, the cam 934 of the drive mechanism 93 is configured as a double cam, by making the lift amount of each mountain (cam nose) relatively large, while supporting the long stroke of the plunger 94 described above, the large cam Can be avoided. This is because, in the two-crest cam, cam noses are arranged on both sides of the center axis of the cam 934, so even if each crest is raised, the other crest is not affected. Therefore, configuring the cam 934 of the drive mechanism 93 as a double cam also contributes to both a reduction in size of the high-pressure fuel pump 90 and an increase in fuel pressure.

  Since the cam 934 of the drive mechanism 93 configured as a double cam is configured to rotate at a constant speed with respect to the crankshaft 15, the high-pressure fuel pump 90 The fuel is discharged four times. In the four-cylinder four-cycle engine 1, each of the four cylinders 18 can discharge fuel in response to one fuel injection. As described above, the use of the double cam is advantageous in connecting the drive mechanism 93 to the crankshaft 15 as described above.

  The high-pressure fuel pump 90 configured to be able to discharge fuel at a high fuel pressure also has a driving torque that is significantly greater than that of a conventional high-pressure fuel pump. If the high-pressure fuel pump 90 having such a high driving torque is attached to the end of the intake or exhaust camshaft 210 or 220 as in the prior art, it will not be possible to operate the VVT 72 or 74 ( That is, the camshaft 210 or 220 does not rotate). However, as described above, since the high-pressure fuel pump 90 is drivingly connected to the crankshaft 15 as shown in FIG. 13, the operation of the VVTs 72 and 74 attached to the intake and exhaust camshafts 210 and 220 is affected. Absent. In this way, driving and connecting the high-pressure fuel pump 90 that realizes high fuel pressure to the crankshaft 15 is an advantageous configuration for ensuring the operation of the VVTs 72 and 74 attached to the camshaft.

  Note that the operation region (map) shown in FIG. 3 is an exemplification, and the technique disclosed herein is not limited to application to an engine in which the map shown in FIG. 3 is set. The map can be changed as appropriate.

  Further, the technology disclosed herein can be applied not only to the naturally aspirated engine as described above but also to an engine with a supercharger. In the supercharged engine, the CI mode region can be expanded to the high load side.

1 Engine 10 PCM (controller)
15 Crankshaft 18 Cylinder 210 Intake camshaft 220 Exhaust camshaft 72 VVT (intake side)
74 VVT (exhaust side)
80 Injector (fuel injection valve)
800 Fuel passage 801 Seat part 802 Restriction part 803 Enlarged part 81 First solenoid coil 82 Second solenoid coil 83 Needle (valve element)
84 injection port 841 first valve body 842 second valve body 85 case 871 first movable core 872 second movable core 891 first type reinforcing member 892 second type reinforcing member 90 high pressure fuel pump 91 cylinder 911 inlet 92 inlet valve 923 Solenoid coil 93 Drive mechanism 934 Double cam 94 Plunger

Claims (3)

A fuel injection valve for a direct injection engine that directly injects fuel containing gasoline into a cylinder of the engine,
A valve body having a fuel passage provided therein and a plurality of nozzle holes provided at the tip thereof;
A needle disposed in the fuel passage and stroked to open and close each nozzle,
A solenoid coil that is disposed outside the fuel passage and strokes the needle so that the needle opens the nozzle holes when energized.
The maximum fuel pressure in the fuel passage is set to a high fuel pressure of 40 MPa or more,
The fuel passage is
A seat portion that is set to a diameter smaller than the diameter of the basic cylindrical portion at the tip portion of the needle and that opens and closes each nozzle hole when the tip portion is seated and separated; and
A diaphragm portion continuous with the sheet portion;
And an enlarged portion having a diameter larger than that of the throttle portion, and continuous with the throttle portion,
The plurality of injection holes are fuel injection valves for a direct injection engine that communicate with the enlarged portion. The fuel injection valve for a direct injection engine according to claim 1,
The tip of the needle is formed to be tapered,
The needle is a fuel injection valve of a direct injection engine configured such that a middle portion of the tapered tip end portion is seated on the seat portion. The fuel injection valve for a direct injection engine according to claim 1 or 2,
The direct injection engine is a fuel injection valve for a direct injection engine configured to perform compression ignition combustion of a homogeneous lean air-fuel mixture in a predetermined operating region.

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