JP2013024054A - Start control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To always maintain a positional relationship between a fuel spray and a glow plug optimal.SOLUTION: A start control device (100) in a compression self-ignition type internal combustion engine (200) includes: a specifying means which specifies the kinematic viscosity of a fuel to be injected; a determination means which determines a control condition of at least one of a spray means (370), a high pressure pump (350) and a swirl valve (208), the determination means being configured to regulate a spray characteristic on the basis of the specified kinematic viscosity in such a manner that the position of a fuel spray with respect to a glow plug during a period in which the glow plug (219) is used is a desired position; a control means which controls at least one of the spray means (370), high pressure pump (350) and swirl valve (208) in accordance with the determined control condition; an estimation means which estimates the position of the spray to the glow plug on the basis of a characteristic of a drive current (Igp) of the glow plug; and a correction means which corrects the determined control condition in accordance with a deviation between the estimated position and a desired position.

Description

  The present invention relates to a technical field of a start control device in a compression self-ignition internal combustion engine provided with a glow plug.

  As this type of device, Patent Document 1 discloses a diesel engine start control device.

  According to this apparatus, when the glow plug is disposed close to the upstream side of the spray with respect to the flow direction of the swirl flow, when the center of the sphere including the spherical curved surface at the tip of the glow plug is used as the center of the tip, In a cross section passing through the center of the tip and perpendicular to the spraying direction of the spray, an angle formed between a line connecting the center of the tip and the center of the spray and a line passing through the center of the spray and perpendicular to the flow direction of the swirl is 55 ° to A glow plug is arranged so as to be in a range of 70 °. As a result, the air warmed by the glow plug can be supplied to the spray without obstructing the air flow, and good startability is ensured.

JP 2000-230471 A

  The fuel spray characteristics in the cylinder vary depending on the kinematic viscosity of the fuel. However, the apparatus disclosed in Patent Document 1 does not take into account the change in the fuel spray characteristics due to the change in kinematic viscosity. For this reason, with the apparatus disclosed in Patent Document 1, the positional relationship between the fuel spray and the glow plug cannot always be maintained optimally.

  The present invention has been made in view of such problems, and always maintains the positional relationship between the fuel spray and the glow plug so as to be optimal, thereby suppressing a decrease in fuel ignitability during cold start. It is an issue to provide.

  In order to solve the above-described problems, a start control device according to the present invention includes a swirl valve capable of controlling the flow speed of an intake swirl flow formed in a cylinder, and thermal energy corresponding to a drive current for the gas in the cylinder. A glow plug capable of supplying fuel, a storage means capable of storing fuel at a fuel pressure equal to or higher than the cylinder pressure of the cylinder, a high-pressure pump capable of controlling the fuel pressure, and the stored fuel can be injected into the cylinder as a spray A start control device for a compression self-ignition internal combustion engine comprising injection means, wherein the specific means for specifying the kinematic viscosity of the injected fuel and the glow plug in the period during which the glow plug is used The injection means, the high-pressure pump, and the swirl that define the spray characteristics related to the spray based on the specified kinematic viscosity so that the spray position becomes a desired position. Determining means for determining at least one control condition, control means for controlling the at least one according to the determined control condition, and estimating a spray position with respect to the glow plug based on characteristics of the drive current An estimation means, and a correction means for correcting the determined control condition in accordance with a deviation between the estimated position and the desired position (Claim 1).

  The internal combustion engine according to the present invention is a compression ignition type internal combustion engine such as a diesel engine, and in particular, a swirl valve capable of controlling the flow rate of a swirl flow and in-cylinder gas (intake, spray, or a mixed gas thereof). A glow plug that can supply thermal energy, a high-pressure pump that boosts the low-pressure fuel fed from the fuel tank, storage means such as a common rail that can store high-pressure fuel discharged from the high-pressure pump, and fuel in the cylinder The engine includes a direct injection injector capable of injection. Insofar as there is no restriction on the type of fuel used in the internal combustion engine according to the present invention. That is, the internal combustion engine according to the present invention can use light oil, gasoline, alcohol, or a mixed fuel thereof as the fuel.

  A start control device according to the present invention is a device that improves fuel ignitability at the time of start-up in such an internal combustion engine, or suppresses reduction in fuel ignitability, and as a preferred embodiment, for example, one or more A single or a plurality of ECUs (Electronic Controlled Units), a computer system, and the like having a central processing unit (CPU), a micro processing unit (MPU), various processors, various controllers, and the like can be employed. In addition, various storage means such as a ROM (Read Only Memory), a RAM (Random Access Memory), a buffer memory, or a flash memory can be appropriately attached to these. The start control device according to the present invention may be configured as a part of a computer device that controls other parts (for example, a valve system, an ignition system, or a cooling system) of the internal combustion engine.

  In order to improve the ignitability of the fuel by supplying thermal energy through the glow plug and thus improve the startability, the position of the fuel spray with respect to the glow plug is important. The optimum value for the position of the spray with respect to the glow plug is, of course, determined experimentally, empirically or theoretically and is not necessarily unambiguous, but in any case, in order to improve startability, the position of the spray It is important to ensure sufficient controllability.

  In order to ensure the position controllability of the spray, it is necessary to grasp the dynamic behavior or state of the spray in the cylinder (these are collectively expressed as “spray characteristics” as appropriate). For example, such spray characteristics include penetration (spray reach or spray length), spray angle (angle formed by the spray with respect to the nozzle hole), spray movement angle (angle where the spray has moved by the swirl flow), etc. It may suitably be included. The spray characteristics generally include controllable elements and inherent elements related to the injection means that can be determined to some extent in the operation control of the internal combustion engine, such as fuel pressure and injection amount (in particular, the nozzle hole length is referred to as L / D, the nozzle hole diameter Etc.) and the like. Also, the spray characteristics are variable with respect to the gas state in the cylinder. The gas state in the cylinder defined here is a gas state that can affect the dynamic behavior of the spray. As a preferred form, for example, the gas temperature in the cylinder (in-cylinder temperature), the gas density (In-cylinder density) or gas pressure (in-cylinder pressure).

  However, the spray position control accuracy is not always sufficient simply by making the spray position relative to the glow plug variable in accordance with these factors. This is because the spray characteristics change according to the viscosity of the fuel. However, even if it says viscosity, the static viscosity (absolute viscosity) which is a viscosity intrinsic to a substance is not necessarily an effective index in this case. For example, even if the static viscosity is small, if the fuel is reasonably light, its dynamic characteristics will be slow. On the other hand, if the fuel is reasonably heavy even if the static viscosity is large, its dynamic characteristics will be sharp. . That is, since the fuel spray injected from the injection means is a fluid, an indicator of the dynamic viscosity of the fluid is required to accurately grasp the fuel spray characteristics.

  In view of this point, the start control device according to the present invention has a configuration in which the kinematic viscosity of the fuel is specified by the specifying means. The kinematic viscosity conceptually means the degree of fluid dynamic viscosity (difficulty of movement), and the value obtained by dividing the static viscosity by the density of the fluid under the same conditions (for example, temperature and pressure) ( Ie, static viscosity / density). The kinematic viscosity of the fuel specified by the specifying means means the kinematic viscosity defined in this way or the physical quantity, control quantity or index value associated with the kinematic viscosity one-to-one, one-to-many, many-to-one or many-to-many. Means.

  The kinematic viscosity affects, for example, fuel evaporation characteristics (for example, evaporation temperature) in the cylinder, and the evaporation characteristics affect, for example, the penetration described as an example of the spray characteristics. Further, for example, the spray angle of the fuel spray changes with respect to the kinematic viscosity. That is, it can be said that the kinematic viscosity of the fuel as an index of the difficulty of movement of the actually injected fuel is an indispensable element necessary for estimating the spray characteristics.

  According to the present invention, based on the specified kinematic viscosity, or on the basis of the spray characteristic estimated from the specified kinematic viscosity, at least of the injection means, the high pressure pump, and the swirl valve that define the spray characteristics. One control condition is determined. More specifically, this control condition is determined so that the position of the spray with respect to the glow plug is a desired position (which is ambiguous as described above). Therefore, ideally, the position of the spray with respect to the glow plug can be maintained at a desired position by the control means controlling at least one according to the determined control condition.

  By the way, the control condition determined by the determining means is, in other words, the control condition determined by a feed forward (F / F) method, so that the position of the spray with respect to the glow plug is truly maintained at a desired position. Whether it is present or not cannot be known only by control by the control means. In view of this point, in the start control device according to the present invention, the correcting means appropriately corrects the determined control condition. Here, in particular, the correction means is configured to correct the position of the spray relative to the glow plug estimated by the estimation means by feedback (F / B) to the determined control condition.

  Here, according to the knowledge based on the applicant's long-term research, the driving current of the glow plug, for example, the peak value, the rate of time change, the time transition, etc., changes according to the degree of contact between the glow plug and the spray. To do. For example, the peak value of the drive current increases as the degree of contact of the glow plug with the spray increases. Therefore, if the characteristics of the drive current at a desired position are obtained experimentally, empirically, or theoretically in advance, the glow plug and the spray are actually used under the control conditions calculated by the F / F method as described above. It is possible to accurately grasp how far the positional relationship is with respect to the desired positional relationship.

  That is, according to the start control device of the present invention, it is possible to always maintain the optimum positional relationship between the glow plug and the spray during the start period in which the glow plug is operated, particularly during the cold start period. It is possible to improve the above, or to suppress a decrease in startability.

  The “specification” according to the present invention is a concept that means that a specific target is determined directly or indirectly as a reference value that can be used for control regardless of the practical process. Therefore, the specifying means for specifying the kinematic viscosity may be a detecting means such as a sensor for detecting the kinematic viscosity of the fuel, or may be a means for acquiring a detection result from this type of detecting means provided separately. Further, it may be a means for calculating according to an algorithm, an arithmetic expression or the like that has been established in advance. Alternatively, it may be a means for selecting a corresponding value from a control map or the like set in advance based on the reference value.

  In one aspect of the start control apparatus according to the present invention, the estimation means estimates the position based on a degree of change in the drive current in a period corresponding to the fuel injection period.

  According to this aspect, the estimation means may be a period corresponding to the fuel injection period (which may be the injection period itself, but preferably is a drive that is experimentally, empirically or theoretically obtained in advance. The position of the spray with respect to the glow plug is estimated on the basis of the degree of change in the drive current during a period in which the change in current can be noticeable. Since the degree of change in the drive current represents the behavior of the drive current in a certain time region, higher accuracy can be ensured than in the determination based on a simple peak value.

  In another aspect of the start control device according to the present invention, the control condition of the injection means is the fuel injection amount, the control condition of the high pressure pump is the fuel pressure, and the control condition of the swirl valve is the flow rate. Yes, the determining means determines (1) the injection amount, (2) determines the injection amount and the fuel pressure when the determined injection amount does not satisfy the constraints, and (3) the determined When the injection amount and the fuel pressure do not satisfy the constraints, the injection amount, the fuel pressure, and the flow velocity are determined (Claim 3).

  According to this aspect, when the priority is given to the control conditions in the order of the injection amount, the fuel pressure, and the flow velocity, and the required injection amount does not satisfy the physical or control restrictions of the injection means, the injection amount In addition, control of fuel pressure is allowed. Similarly, when at least one of the required values of the injection amount and the fuel pressure does not satisfy physical or control restrictions, the control of the flow rate of the swirl flow is permitted in addition to the injection amount and the fuel pressure. As described above, efficient start control can be performed by selecting the control conditions in order from the element having a limited influence on the combustion state of the internal combustion engine.

  In another aspect of the start control device according to the present invention, the injection means includes a plurality of injection holes that are arranged circumferentially along the inner wall of the cylinder when the inside of the cylinder is viewed from below. The determining means is: (1) Out of the plurality of nozzle holes, a central axis of the spray when the inside of the cylinder is viewed from the lower surface is downstream of the glow plug with respect to the direction of the swirl flow In the case where the control condition is determined for the spray corresponding to the closest downstream nozzle hole and the control condition determined for the spray corresponding to the downstream nozzle hole does not satisfy the constraint, (2) Of the plurality of nozzle holes, the central axis of the spray when the inside of the cylinder is viewed from the lower surface is the upstream nozzle hole closest to the glow plug on the upstream side with respect to the direction of the swirl flow. The corresponding jet For determining the control condition (claim 4).

  The spray corresponding to the upstream injection hole closest to the glow plug in the swirl direction upstream with respect to the glow plug is qualitatively shown in the bottom view when the central axis of the injection hole (the central axis of the spray when there is no swirl flow) Is a spray that approaches the glow plug in a swirl style. On the other hand, the spray corresponding to the downstream nozzle hole whose center axis is closest to the glow plug on the downstream side in the swirl direction is qualitatively spray sprayed away from the glow plug in the swirl flow. It is. Therefore, from the viewpoint of effective use of the glow plug, it is better to control the positional relationship between the spray corresponding to the downstream injection hole and the glow plug. According to this aspect, the order of the control process is defined from such a viewpoint, and the start time can be shortened as much as possible by efficiently using the glow plug.

  Such an operation and other advantages of the present invention will become apparent from the embodiments described below.

1 is a schematic configuration diagram conceptually showing a configuration of an engine system according to an embodiment of the present invention. It is a schematic sectional drawing of the engine in the engine system of FIG. It is a schematic block diagram which shows notionally the structure of the fuel-injection system in the engine system of FIG. It is a schematic block diagram of the high pressure pump in the fuel-injection system of FIG. It is a bottom view schematic sectional drawing of the direct injection injector in the fuel-injection system of FIG. 2 is a flowchart of a fuel injection control process executed by an ECU in the engine system of FIG. It is a conceptual diagram of the map for estimation used for estimation of a spray characteristic. It is a flowchart of the control condition calculation process in the fuel injection control process of FIG. It is a flowchart of the control condition calculation process of the upstream spray in the fuel injection control process of FIG. It is a conceptual diagram of the control condition in the control condition calculation process of FIG. 10 is a concept of control conditions in the upstream spray control condition calculation process of FIG. 9. It is a figure which illustrates the time characteristic of the glow plug drive current with respect to the spray position. It is a figure explaining the spray position in connection with the time characteristic of FIG.

<Embodiment of the Invention>
Embodiments of the present invention will be described below with reference to the drawings.

<Configuration of Embodiment>
First, the configuration of an engine system 10 according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic configuration diagram conceptually showing the configuration of the engine system 10.

  In FIG. 1, an engine system 10 is mounted on a vehicle (not shown) and includes an ECU 100, an engine 200, a fuel injection system 300, and an EGR (Exhaust Gas Recirculation) device 400.

  The ECU 100 is an electronic control unit that includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM, and the like, and is configured to be able to control the operation of the engine system 10. It is an example. The ECU 100 is configured to execute a fuel injection control process, which will be described later, according to a control program stored in the ROM.

  The ECU 100 is an integrated electronic control unit that can function as an example of each of the “specifying means”, “determination means”, “control means”, “estimation means”, and “correction means” according to the present invention. The physical, mechanical, and electrical configurations of the respective means according to the invention are not limited to this, and these various means include various computer systems such as a plurality of ECUs, various processing units, various controllers, or microcomputer devices. Etc. may be configured.

  The engine 200 is a diesel engine as an example of the “internal combustion engine” according to the present invention. Here, a detailed configuration of the engine 200 will be described with reference to FIG. FIG. 2 is a schematic cross-sectional view of the engine 200.

  In the cylinder 202 accommodated in the cylinder block 201, the engine 200 compresses and ignites a mixture of light oil (an example of “fuel” according to the present invention) injected from a direct injection injector 370 described later and intake air. In addition, the compression self-ignition internal combustion engine is configured to be able to convert the reciprocating motion of the piston 203 generated in accordance with the explosive force accompanying the combustion into the rotational motion of the crankshaft 205 via the connecting rod 204.

  In the vicinity of the crankshaft 205, a crank position sensor 206 for detecting the rotational position (ie, crank angle) of the crankshaft 205 is installed. The crank position sensor 206 is electrically connected to the ECU 100, and the detected crank angle of the engine 200 is referred to the ECU 100 at a constant or indefinite period.

  The engine 200 is an in-line multi-cylinder diesel engine in which a plurality of cylinders 202 are arranged in a direction perpendicular to the paper surface. However, since the configurations of the individual cylinders 202 are the same, only one cylinder 202 is described in FIG. To do. Further, such a configuration is only an example that the “internal combustion engine” according to the present invention can take.

  In the engine 200, air sucked from the outside is guided to the intake pipe 207. On the upstream side of the intake port 209 in the intake pipe 207, an SCV (Swirl Control Valve) 208 for adjusting the amount of fresh air (fresh air amount) guided to the intake port 209 is disposed. The SCV 208 is configured such that its drive state is controlled by an actuator (not shown) that is electrically connected to the ECU 100.

  Here, the intake port 209 receives a swirling flow of the intake air (hereinafter, referred to as “intake” as appropriate) of fresh air that has passed through the SCV 208 and the EGR gas described later (hereinafter referred to as “intake” as appropriate) (Referred to as “swirl flow” as appropriate) to form a curved surface. The SCV 208 can change the flow velocity Vsw of the swirl flow according to the valve opening (SCV opening). In addition, this swirl flow is formed along the cross section which followed the paper surface left-right direction substantially. In other words, the swirl flow is formed along the curved inner wall of the substantially cylindrical cylinder 202.

  The communication state between the cylinder 202 and the intake port 209 is controlled by opening and closing the intake valve 210, and the intake air described above is taken into the cylinder 202 when the intake valve 210 is opened. The intake valve 210 is opened and closed in accordance with a cam profile of an intake cam 211 having an elliptical shape in cross section attached to an intake camshaft ICS (not shown) connected to the crankshaft 205 via a sprocket (not shown). It is configured to be driven.

  The fuel injection valve of the direct injection injector 370 is exposed in the cylinder 202, and the fuel spray injected from the direct injection injector 370 is mixed with the intake air sucked through the intake port 209 in the cylinder 202. Thus, the above-mentioned air-fuel mixture is obtained. The air-fuel mixture burned in the cylinder 202 becomes exhaust gas, and is guided to the exhaust pipe 214 via the exhaust port 213 when the exhaust valve 212 that opens and closes in conjunction with the opening and closing of the intake valve 210 is opened.

  An exhaust pressure sensor 215 configured to detect the exhaust pressure Pex of the engine 200 is installed in the exhaust pipe 214. In addition, the water jacket stretched around the cylinder block 201 containing the cylinder 202 is cooled to detect the cooling water temperature Tw related to the cooling water (LLC) circulated and supplied to cool the engine 200. A water temperature sensor 216 is provided. Further, the combustion chamber, which is a space defined by the upper surface portion of the piston 203 and the inner wall portion of the cylinder 202 in a state where the piston 203 is located at TDC (Top Death Center), has a temperature inside the cylinder 202. The sensor terminal of the in-cylinder temperature sensor 217 capable of detecting a certain in-cylinder temperature Tcy is exposed. Further, an in-cylinder pressure sensor 218 capable of detecting an in-cylinder pressure Pcy that is a pressure inside the cylinder 202 is disposed in the combustion chamber. Each of these sensors is electrically connected to the ECU 100, and the detected exhaust pressure Pex, cooling water temperature Tw, in-cylinder temperature Tcy, and in-cylinder pressure Pcy are respectively referred to by the ECU 100 at a constant or indefinite period. It is the composition which becomes.

  On the other hand, the engine 200 includes a glow plug 219. The glow plug 219 is electrically connected to the ECU 100 via a driving system (not shown), and the ECU 100 controls the driving system so that the glow plug 219 glows red according to the driving current Igp supplied from the driving system, A ceramic body in which the heat coil is embedded, and the heat coil is exposed to the combustion chamber. The heat coil is in a high temperature state of about several hundred degrees Celsius when energized, and is configured to be able to raise the temperature of the in-cylinder gas by directly or indirectly supplying thermal energy to the in-cylinder gas in the combustion chamber. The driving current Igp is variable according to the thermal load of the ceramic body that houses the heat coil. In other words, the greater the degree of contact with the cold fuel spray compared to the temperature of the heat coil, the higher the drive current Igp is controlled to compensate for the deprived heat. The characteristic of the drive current Igp is used in a fuel injection control process described later.

  The EGR device 400 includes an EGR pipe 410, an EGR cooler 420, and an EGR valve 430.

  The EGR pipe 410 is a metal tubular member having one end connected to the exhaust port 213 and the other end connected to the intake port 209. The exhaust port 213 and the intake port 209 are configured to communicate with each other through the EGR pipe 410 when the EGR valve 430 is opened.

  The EGR cooler 420 is a water-cooled cooling device that cools a relatively high-temperature EGR gas immediately after exhaust by heat exchange with cooling water.

  The EGR valve 430 is an electromagnetic on-off valve device that can continuously change the communication area between the exhaust port 213 and the intake port 209 via the EGR pipe 410. A driving device (not shown) that drives the EGR valve 430 (for example, a solenoid) is electrically connected to the ECU 100, and the EGR opening Aegr that is the opening of the EGR valve 430 can be controlled by the ECU 100. . The “opening degree” means the degree of valve opening, and the EGR opening degree Aegr is such that Aegr = 0 (%) is fully closed (or fully open) and Aegr = 100 (%) is fully open (or Fully closed). In any case, the communication cross-sectional area Segr between the upstream side (exhaust port 213 side) and the downstream side (intake port 209 side) across the EGR valve 430 corresponds to the EGR valve opening degree Aegr on a one-to-one basis.

  In the EGR device 400, a part of the exhaust discharged to the exhaust port 213 is EGR according to the pressure difference between the exhaust pressure Pex and the intake pressure Pin which is the pressure of the intake port 209, and the EGR opening Aegr. It is circulated as a gas to the intake port 209.

  Next, the configuration of the fuel injection system 300 will be described with reference to FIG. FIG. 3 is a schematic configuration diagram conceptually showing the fuel injection system 300. In addition, in the same figure, the same code | symbol is attached | subjected about the location which overlaps with each figure mentioned above, and the description is abbreviate | omitted suitably.

  3, the fuel injection system 300 includes a fuel tank 310, a feed pipe 320, a feed pump 330, a feed pressure sensor 340, a high pressure pump 350, a common rail 360, a direct injection injector 370, a rail pressure sensor 380, and a kinematic viscosity sensor 390. .

  The fuel tank 310 is a tank that stores fuel (light oil in the present embodiment).

  The feed pipe 320 is a metal tubular member having one end connected to the fuel tank 310 and the other end connected to the high-pressure pump 350.

  The feed pump 330 is a low-pressure electric pump device configured to pump fuel from the fuel tank 310 and supply the fuel to the feed pipe 320 at a desired fuel discharge speed (discharge amount per hour). The fuel discharge speed of the feed pump 330 is controlled by a drive device (not shown) that is electrically connected to the ECU 100. The feed pump 330 can variably control the feed pressure Pfd that is the fuel pressure in the feed pipe 320 through the control of the fuel discharge speed.

  The feed pressure sensor 340 is a sensor configured to be able to detect the above-described fuel feed pressure Pfd. The feed pressure sensor 340 is electrically connected to the ECU 100, and the detected feed pressure Pfd is referred to by the ECU 100 at a constant or indefinite period.

  The high-pressure pump 350 is a mechanical pump device for boosting the fuel supplied through the feed pump 330.

  Here, the configuration of the high-pressure pump 350 will be described with reference to FIG. FIG. 4 is a schematic configuration diagram conceptually showing the configuration of the high-pressure pump 350. In addition, in the same figure, the same code | symbol is attached | subjected about the location which overlaps with each figure mentioned above, and the description is abbreviate | omitted suitably.

  In FIG. 4, the high-pressure pump 350 includes an electromagnetic metering valve 351, a suction valve 352, a cylinder 353, a plunger 354, a pressurizing chamber 355, a cam 356, a discharge valve 357, and a high-pressure pipe 358.

  The electromagnetic metering valve 351 is an electromagnetic open / close valve that is provided in the feed pipe 320 and adjusts the flow rate of the fuel (low pressure fuel) having the feed pressure Pfd that is sent out by the feed pump 320. The flow rate of the low-pressure fuel pumped up from the fuel tank 310 by the feed pump 320 is adjusted by the electromagnetic metering valve 351 and supplied to the pressurizing chamber 355 to which one end of the feed pipe 320 is connected. The electromagnetic metering valve 351 is electrically connected to the ECU 100, and the drive duty that defines the valve opening period is controlled by the ECU 100.

  Plunger 354 is a pressurizing member installed in cylinder 353, and a rod-like member connected to the lower end is fixed to intake camshaft ICS of engine 200 and rotates in conjunction with the rotation of intake camshaft ICS. As shown, the upper end of the cam 356 having an elliptical shape reciprocates in the vertical direction in the figure, and the upper end thereof is shown in the figure TDC (Top Death Center) and the figure BDC (Bottom Death Center: bottom dead center). ).

  The pressurizing chamber 355 is a space defined by the inner wall portion of the cylinder 353 and the upper end portion of the plunger 354, and is a space whose volume changes in accordance with the reciprocation of the plunger 354 described above.

  The fuel metered by the electromagnetic metering valve 351 is sucked into the pressurizing chamber by pushing the suction valve 352 open when the plunger 354 moves from the TDC to the BDC in the cylinder 353 (that is, during the decompression period). The Thereafter, when the plunger 354 moves from the BDC toward the TDC in the cylinder 353 (ie, during the pressurization period), the fuel inside the pressurizing chamber 355 is compressed (ie, pressurized) by the plunger 354. The pressurized fuel is configured to push open the discharge valve 357 to be supplied to the high pressure pipe 358 and to be pumped to the common rail 360 connected to the high pressure pipe 358.

  The high-pressure pump 350 illustrated here is an example of a high-pressure pump device in the in-cylinder injection unit that directly injects the fuel into the cylinder 202, and may take other known modes.

  Returning to FIG. 3, the common rail 360 is a fuel buffer for accumulating the high-pressure fuel supplied from the high-pressure pump 350 and stably supplying it to the plurality of direct injection injectors 370. The rail pressure Pcr (Pcr> Pfd), which is the pressure of the high-pressure fuel stored in the common rail 360, is detected by the rail pressure sensor 380. The rail pressure sensor 380 is electrically connected to the ECU 100, and the detected rail pressure Pcr is referred to by the ECU 100 at a constant or indefinite period. The ECU 100 can maintain the rail pressure Pcr at a desired target pressure by controlling the driving load of the high-pressure pump 350 by driving control of the electromagnetic metering valve 351. The rail pressure Pcr is an example of the “fuel pressure” according to the present invention.

  The kinematic viscosity sensor 390 is a sensor configured to be able to detect the kinematic viscosity Vk of the high-pressure fuel stored in the common rail 360. The kinematic viscosity sensor 390 is electrically connected to the ECU 100, and the detected kinematic viscosity Vk of the high-pressure fuel is grasped by the ECU 100 at a constant or indefinite period. The kinematic viscosity sensor 390 is not necessarily provided on the common rail 360, but is provided on a high pressure fuel pipe connecting the common rail 360 and the high pressure pump 350, a high pressure fuel pipe connecting the common rail 360 and the direct injection injector 370, or the like. It may be arranged.

  The direct injection injector 370 is a fuel injection device that is connected to the common rail 360 and is an example of the “injection means” according to the present invention.

  The direct injection injector 370 is provided for each cylinder 202, and the fuel injection valve 371 of each direct injection injector 370 is exposed inside each cylinder 202 as described above. The direct injector 370 is configured to be able to inject an amount of fuel determined by the valve opening period of the fuel injection valve and the rail pressure Pcr into the cylinder 202 as a spray. The direct injection injector 370 is a so-called porous injection device, and a plurality of injection holes for fuel injection in the fuel injection valve are formed circumferentially along the inner wall (side wall) of the cylinder 202 formed in a circumferential shape. Has been.

  Supplementing the configuration of the direct injection injector 370, the direct injection injector 370 includes an electromagnetic valve that operates based on a command supplied from the ECU 100, and a nozzle that injects fuel when the electromagnetic valve is energized (both not shown). Is provided. The solenoid valve is configured to be able to control the communication state between the pressure chamber to which the high pressure fuel accumulated in the common rail 360 is applied and the low pressure side low pressure passage connected to the pressure chamber. The pressure chamber and the low-pressure passage are communicated with each other, and the pressure chamber and the low-pressure passage are blocked from each other when energization is stopped.

  On the other hand, the nozzle has a built-in needle for opening and closing the nozzle hole, and the fuel pressure in the pressure chamber urges the needle in the valve closing direction (direction in which the nozzle hole is closed). Therefore, when the pressure chamber communicates with the low pressure passage by energizing the solenoid valve, and the fuel pressure in the pressure chamber decreases, the needle rises in the nozzle and opens (opens the nozzle hole), so that the common rail 360 opens. The supplied high-pressure fuel is injected from the injection hole. In addition, when the energization of the solenoid valve is stopped, the pressurization chamber and the low pressure passage are cut off from each other and the fuel pressure in the pressure chamber rises, and the needle is lowered in the nozzle to close the valve, thereby terminating the injection. It has become.

  Here, the fuel injection valve 371 will be described with reference to FIG. Here, FIG. 5 is a schematic cross-sectional view of the fuel injection valve 371 as viewed from below, as viewed from the bottom (ie, toward the combustion chamber) inside the cylinder 202. In the figure, the same reference numerals are given to the same portions as those in the above-described drawings, and the description thereof will be omitted as appropriate.

  In FIG. 5, the fuel injection valve 371 has a circular shape when viewed from the bottom, and a plurality of injection holes 371 i (i = 1, 2,..., 8) are formed on the outer peripheral portion. In the figure, only the injection hole 3711 and the injection hole 3712 are denoted by reference numerals. The shape of the intake port 209, the direction of the swirl flow formed in the cylinder by the action of the SCV 208, and the position of the glow plug 219 are as shown in the figure, and the injection hole 3711 has the injection hole central axis indicated by the chain line downstream in the swirl direction. Is a nozzle hole closest to the glow plug, and is an example of the “downstream nozzle hole” according to the present invention. In the present embodiment, the angle formed by the injection hole central axis of the injection hole 3711 and the line connecting the center of the fuel injection valve 371 and the glow plug 219 is expressed as a glow plug attachment angle θg.

  In the present embodiment, the injection pressure Pinj of the fuel injected from each injection hole of the direct injection injector 370 and the rail pressure Pcr are treated synonymously.

<Operation of Embodiment>
Next, a fuel injection control process executed by the ECU 100 will be described as an operation of the present embodiment with reference to FIG. FIG. 6 is a flowchart of the fuel injection control process.

  In FIG. 6, the ECU 100 reads various index values representing the in-cylinder state of the cylinder 202 (step S101). This index value is, for example, the cooling water temperature Tw or the lubricating oil temperature (in this embodiment, it is replaced by the cooling water temperature). Note that the in-cylinder temperature Tcy may be used as the index value of the in-cylinder state.

  When the in-cylinder state is read, ECU 100 determines whether engine 200 is in a cold start state (step S102). If not in the cold start state (step S102: NO), the process returns to step S101. When the engine 200 is in a cold start state (step S102: YES), the ECU 100 controls the glow plug 219 to be in an on state (that is, an operating state) (step S103).

  When the glow plug 219 is controlled to be in the ON state, the ECU 100 determines the kinematic viscosity Vk of the high-pressure fuel stored in the common rail 360 based on the sensor output of the kinematic viscosity sensor 390 (step S104). Step S104 is an example of the operation of the “specifying means” according to the present invention.

  Here, the kinematic viscosity of the high-pressure fuel is directly detected by the kinematic viscosity sensor 390, but it goes without saying that a practical aspect that can be taken by the specific means according to the present invention is not limited to this. For example, the ECU 100 may calculate the kinematic viscosity according to the following equation (1) based on the static viscosity Vs of the fuel and the fuel density Df in the common rail 360.

Vk = Vs / Df (1)
Here, the static viscosity Vs is a value specific to the fuel type, excluding unexpected factors such as deterioration over time, and can be stored in advance as a fixed value for each fuel used. On the other hand, since the fuel density Df is a mass per unit volume, the fuel discharge amount or fuel discharge speed (that is, supply amount) of the high-pressure pump 350, the fuel injection amount (that is, the discharge amount) of each direct injector 370, and It can be calculated from the volume of the common rail 360. Alternatively, if the relationship between the rail pressure Pcr and the mass of the common rail 360 is obtained experimentally, empirically or theoretically in advance, the fuel density Df is obtained based on the rail pressure Pcr detected by the rail pressure sensor 380. It is also possible.

  Alternatively, the kinematic viscosity Vk can also be obtained from the needle lift amount when the means for detecting the needle lift amount of the direct injection injector 370 is installed. The magnitude of the needle lift amount corresponds to the kinematic viscosity Vk. Therefore, if a map or the like that defines the correspondence between the needle lift amount and the kinematic viscosity Vk is prepared in advance, the kinematic viscosity Vk can be obtained by selecting a corresponding value from the map. The kinematic viscosity Vk also affects the degree of fluctuation of the rail pressure Pcr in the common rail 360. That is, when the time characteristic of the detected rail pressure Pcr is a kind of variation index value, the time characteristic changes according to the kinematic viscosity Vk. Therefore, the kinematic viscosity Vk can also be obtained from the degree of fluctuation of the rail pressure Pcr.

  When the kinematic viscosity Vk is determined, the operating conditions of the engine 200 are further read (step S105). The operating condition read in step S105 is a condition necessary for determining the target fuel injection amount Qmtg, and means, for example, the engine rotational speed NE and an operation amount (accelerator opening degree Ta) of an unillustrated accelerator pedal.

  The ECU 100 estimates fuel spray characteristics based on various factors including the kinematic viscosity Vk determined in step S104 (step S106). Although the fuel spray characteristics are ambiguous, in the present embodiment, the spray angle θsp, the penetration PN, and the spray movement angle θsw are estimated. In estimating these spray characteristics, the ECU 100 refers to an estimation map prepared in advance for each spray characteristic. That is, the ECU 100 refers to the spray angle estimation map, the penetration estimation map, and the spray movement angle estimation map.

  Here, with reference to FIG. 7, the map for estimation used for estimation of these spray characteristics is demonstrated. FIG. 7 is a conceptual diagram of the estimation map.

  In FIG. 7, FIGS. 7 (a), 7 (b) and 7 (c) show the concept of a spray angle estimation map, a penetration estimation map and a spray movement angle estimation map, respectively.

  In FIG. 7A, the diagram on the left side in the drawing is a diagram showing the change characteristic of the spray angle θsp with respect to the injection amount Q when the kinematic viscosity Vk is Vka and Vkb (Vka <Vkb). The change characteristic corresponding to the kinematic viscosity Vka is represented as L_Vka1 (see solid line) in the figure, and the change characteristic corresponding to the kinematic viscosity Vkb is represented as L_Vkb1 (see broken line) in the figure. Further, the diagram on the right side in the figure is a diagram showing a change characteristic of the spray angle θsp with respect to the rail pressure Pcr when the kinematic viscosity Vk is Vka and Vkb (Vka <Vkb). The change characteristic corresponding to the kinematic viscosity Vka is represented as L_Vka2 (see solid line) in the figure, and the change characteristic corresponding to the kinematic viscosity Vkb is represented as L_Vkb2 (see broken line) in the figure. As shown in the figure, the spray angle θsp varies depending on the kinematic viscosity Vk even if the injection amount Q and the rail pressure Pcr are constant. Therefore, even if it is going to control the position of a spray based on the spray characteristic which does not consider dynamic viscosity Vk, a spray cannot be maintained in an optimal position.

  In the spray angle estimation map, the relationship illustrated in FIG. 7A is digitized and stored. At this time, it goes without saying that the kinematic viscosity Vk is not limited to the two shown in the figure but is defined in more stages.

  In FIG. 7B, the diagram on the left side of the drawing is a diagram showing the time variation characteristics of the penetration PN when the kinematic viscosity Vk is Vka and Vkb (Vka <Vkb). The change characteristics corresponding to the kinematic viscosity Vka are L_Vka3 and L_Vka4 (see the solid line) in the figure, the former corresponding to the injection amount Qa and the latter corresponding to the injection amount Qb (Qb <Qa). The change characteristics corresponding to the kinematic viscosity Vkb are L_Vkb3 and L_Vkb4 (see broken lines) in the figure, and the former corresponds to the injection amount Qa and the latter corresponds to the injection amount Qb (Qb <Qa). On the other hand, the diagram on the right side in the figure is also a diagram showing the time variation characteristics of the penetration PN when the kinematic viscosity Vk is Vka and Vkb (Vka <Vkb). However, the change characteristics corresponding to the kinematic viscosity Vka are L_Vka5 and L_Vka6 (see the solid line) shown in the figure, the former corresponding to the rail pressure Pcra and the latter corresponding to the rail pressure Pcrb (Pcrb <Pcra). The change characteristics corresponding to the kinematic viscosity Vkb are L_Vkb5 and L_Vkb6 (see the broken line) shown in the figure, and the former corresponds to the rail pressure Pcra and the latter corresponds to the rail pressure Pcrb (Pcrb <Pcra). As shown in the figure, the penetration PN varies depending on the kinematic viscosity Vk even if the injection amount Q and the rail pressure Pcr are constant. Therefore, even if it is going to control the position of a spray based on the spray characteristic which does not consider dynamic viscosity Vk, a spray cannot be maintained in an optimal position.

  In the penetration estimation map, the relationship illustrated in FIG. 7B is digitized and stored. At this time, it goes without saying that the kinematic viscosity Vk is not limited to the two shown in the figure but is defined in more stages.

  On the other hand, in FIG.7 (c), the figure on the left side in the figure is a diagram showing the time variation characteristic of the spray movement angle θsw when the flow velocity Vsw of the swirl flow is Vswa. A change characteristic corresponding to the flow velocity Vswa is represented as L_swa (see a solid line) in the figure. In addition, the diagram on the right side in the figure is a diagram showing the temporal variation characteristic of the spray movement angle θsw when the swirl flow velocity Vsw is Vswb (Vswb> Vswa). The change characteristic corresponding to the flow velocity Vswb is represented as L_swb (see solid line) in the figure. As shown in the figure, the spray movement angle θsw varies depending on the swirl flow velocity Vsw. Therefore, even if it is going to control the position of a spray based on the spray characteristic which does not consider the flow velocity Vsw, a spray cannot be maintained in an optimal position.

  In the spray movement angle estimation map, the relationship illustrated in FIG. 7C is digitized and stored. At this time, it goes without saying that the flow velocity Vsw is not limited to the two shown in the figure but is defined in more stages.

  Thus, the spray angle θsp and the penetration PN are functions of the kinematic viscosity Vk, the injection amount Q, and the rail pressure Pcr, respectively, and the spray movement angle θsw is a function of the swirl flow velocity Vsw. In the present embodiment, the position of the spray relative to the glow plug can be optimized based on these spray characteristics.

  Returning to FIG. 6, when the fuel spray characteristics that change in accordance with each parameter including the kinematic viscosity Vk are estimated, the ECU 100 executes a control condition calculation process (step S200). The control condition calculation process is a subroutine for calculating a control condition for maintaining the spray position with respect to the glow plug 219 at the optimum position set from the viewpoint of improving ignitability.

  Here, the details of the control condition calculation process will be described with reference to FIG. FIG. 8 is a flowchart of the control condition calculation process.

  In FIG. 8, the ECU 100 first starts calculating the control conditions for the downstream spray (step S201). With reference to FIG. 5, the downstream spray means spray from an injection hole whose injection center line (chain line) is located downstream of the glow plug 219 in the swirl direction, that is, the injection hole 3711. In this case, the nozzle hole 3711 according to the present invention is “the center axis of the nozzle hole when the inside of the cylinder is viewed from below is closest to the glow plug on the downstream side with respect to the direction of the swirl flow. It is an example of a “downstream nozzle hole”.

  The process for calculating the control conditions for the downstream spray is ambiguous, but an example will be described below. The control condition of the downstream spray is determined based on the following equation (2).

a = sin ⁻¹ [{d * sin (θg + θsw)} / {b + r + d * cos (θg + θsw) * tan θsp}] (2)
The parameter values in the above equation (2) are as follows.

a: Glow plug / spray angle b: Glow plug / spray distance d: Distance between the center axis of the glow plug and the nozzle outlet r: Glow plug tip radius θsp: Spray angle θsw: Spray movement angle θg: Glow Plug mounting angle The tip radius r is a fixed value determined by the specifications of the glow plug 219, and the distance d is a fixed value determined by the specifications of the engine 200. The glow plug attachment angle θg is also a fixed value when the glow plug 219 is installed.

  On the other hand, the distance b is one of the elements that define the spray position with respect to the glow plug 219, and a desired value can be set in advance. In this embodiment, b≈0 (b> 0), that is, the spray target position is a position that is almost adjacent to the glow plug 219.

  Following the above process, as a result, the glow plug / spray angle a, which is another element that defines the spray position, is a function of the spray angle θsp and the spray movement angle θsw. Here, the optimum range of the glow plug-spray angle a can be determined experimentally, empirically, or theoretically in advance (for example, 55 ° to 70 °), and finally, control conditions for downstream spraying. The target injection amount Qtg, the target rail pressure Pcrtg, and the target flow velocity Vswgtg that satisfy the relationship between the spray angle θsp and the spray movement angle θsw can be determined.

  In the above example, the control conditions are determined so as to satisfy the spray angle θsp and the spray movement angle θsw, and the penetration PN illustrated in FIG. 7 is not referred to. However, the penetration PN is still an element of the spray state. For example, the control condition may be determined by using the penetration PN and the spray angle θsp as achievement factors, and the penetration PN and the spray movement angle θsw are achieved. There is no problem even if the control condition is determined as an element.

  The calculation of the control condition for the downstream spray based on the above equation (2) is first executed using only the injection amount Q as an operation parameter. When the injection amount Q1 for controlling the position of the downstream spray with respect to the glow plug 219 to a desired position is calculated, the ECU 100 determines whether or not the injection amount Q1 is within the restriction range (step S202). .

  The restriction in this case means a physical restriction on the injection amount and a restriction on the control, and whether or not it is a value that can be realized by causing the direct injection injector 370 to perform multi-stage injection is a main restriction requirement. . The injection amount required for the engine 200 is determined separately from the viewpoint of improving the ignitability, and it is not reasonable to calculate the control condition while ignoring the required injection amount. Therefore, when the injection amount as the control condition is smaller than the original required injection amount, it is necessary to ensure the entire injection amount by multistage injection using a plurality of injection holes. On the contrary, when the injection amount as the control condition is larger than the original required injection amount, the constraint is violated unconditionally.

  When the injection amount Q1 satisfies the restriction (step S202: YES), the ECU 100 sets the target injection amount Qtg of the downstream injection hole to the injection amount Q1 (step S203), and ends the control condition calculation process. On the other hand, when the injection amount Q1 does not satisfy the restriction (step S202: NO), the process proceeds to step S204.

  In step S204, downstream spray control conditions are calculated using the injection amount Q and the rail pressure Pcr as operation parameters. After the injection amount Q2 and the rail pressure Pcr2 for controlling the position of the downstream spray with respect to the glow plug 219 to a desired position are calculated, the ECU 100 determines whether or not the injection amount Q2 and the rail pressure Pcr2 are within the limits. Is determined. The rail pressure Pcr constraint is also defined including physical constraints and control constraints.

  When both the injection amount Q2 and the rail pressure Pcr2 satisfy the constraints (step S204: YES), the ECU 100 sets the target injection amount Qtg of the downstream injection hole to the injection amount Q2, and sets the target rail pressure Pcrtg to the rail pressure Pcr2. After setting (step S205), the control condition calculation process is terminated. On the other hand, when the injection amount Q2 and / or the rail pressure Pcr2 do not satisfy the constraint (step S204: NO), the process proceeds to step S206.

  In step S206, the downstream spray control conditions are calculated using the injection amount Q, rail pressure Pcr, and swirl flow velocity Vsw as operation parameters. After the injection amount Q3, rail pressure Pcr3 and flow velocity Vsw3 for controlling the position of the downstream spray with respect to the glow plug 219 are calculated, the ECU 100 restricts the injection amount Q3, rail pressure Pcr3 and flow velocity Vsw3. It is determined whether it is within the range. The restriction on the flow velocity Vsw is also defined including physical restrictions and control restrictions.

  When the injection amount Q3, rail pressure Pcr3, and flow velocity Vsw3 all satisfy the constraints (step S206: YES), the ECU 100 sets the target injection amount Qtg of the downstream injection hole to the injection amount Q3, and sets the target rail pressure Pcrtg to the rail pressure. Pcr3 is set, the target flow velocity Vsw of the swirl flow is set to the flow velocity Vsw3 (step S207), and the control condition calculation process is terminated.

  On the other hand, when at least one of the injection amount Q3, the rail pressure Pcr3, and the flow velocity Vsw3 does not satisfy the constraint (step S206: NO), the process proceeds to step S300, and the upstream spray control condition calculation process is executed. The upstream spray control condition calculation process is a subroutine for calculating the upstream spray control condition for maintaining the spray position with respect to the glow plug 219 at the optimum position set in terms of improving ignitability. With reference to FIG. 5, the upstream spray means spray from an injection hole whose injection center line (chain line) is located upstream of the glow plug 219, that is, the injection hole 3712. In this case, according to the present invention, the nozzle hole 3712 is closest to the glow plug on the upstream side with respect to the direction of the swirl flow direction when the center axis of the nozzle hole when the inside of the cylinder is viewed from the lower surface. It is an example of an “upstream nozzle hole”.

  Here, with reference to FIG. 9, the details of the control condition calculation processing of the upstream spray will be described. FIG. 9 is a flowchart of the upstream spray control condition calculation process. In FIG. 9, the description of the same parts as in FIG. 8 will be omitted as appropriate.

  In FIG. 9, the ECU 100 first starts calculating the control conditions for the upstream spray (step S301).

  The process for calculating the control conditions for the upstream spray is also ambiguous, but here it is assumed to be the same as the process for calculating the control conditions for the downstream spray.

  The calculation of the upstream spray control condition is first executed using only the injection amount Q as an operation parameter. When the injection amount Q4 for controlling the position of the upstream spray with respect to the glow plug 219 to a desired position is calculated, the ECU 100 determines whether or not the injection amount Q4 is within the restriction range (step S302). .

  When the injection amount Q4 satisfies the restriction (step S302: YES), the ECU 100 sets the target injection amount Qtg of the upstream injection hole to the injection amount Q4 (step S303) and ends the control condition calculation process. On the other hand, when the injection amount Q4 does not satisfy the restriction (step S302: NO), the process proceeds to step S304.

  In step S304, the upstream spray control conditions are calculated using the injection amount Q and the rail pressure Pcr as operation parameters. After calculating the injection amount Q5 and the rail pressure Pcr5 for controlling the upstream spray position with respect to the glow plug 219 to a desired position, the ECU 100 determines whether or not the injection amount Q5 and the rail pressure Pcr5 are within the limits. Is determined.

  When both the injection amount Q5 and the rail pressure Pcr5 satisfy the constraints (step S304: YES), the ECU 100 sets the target injection amount Qtg of the upstream injection hole to the injection amount Q5, and sets the target rail pressure Pcrtg to the rail pressure Pcr5. After setting (step S305), the control condition calculation process is terminated. On the other hand, if the injection amount Q5 and / or the rail pressure Pcr5 do not satisfy the constraint (step S304: NO), the process proceeds to step S306.

  In step S306, the upstream spray control conditions are calculated using the injection amount Q, the rail pressure Pcr, and the swirl flow velocity Vsw as operation parameters. After the injection amount Q6, the rail pressure Pcr6 and the flow velocity Vsw6 for controlling the position of the upstream spray with respect to the glow plug 219 are calculated, the ECU 100 restricts the injection amount Q6, the rail pressure Pcr6 and the flow velocity Vsw6. It is determined whether it is within the range.

  When the injection amount Q6, the rail pressure Pcr6, and the flow velocity Vsw6 all satisfy the constraints (step S306: YES), the ECU 100 sets the target injection amount Qtg of the upstream injection hole to the injection amount Q6 and sets the target rail pressure Pcrtg to the rail pressure. Pcr6 is set, the target flow velocity Vsw of the swirl flow is set to the flow velocity Vsw6 (step S307), and the control condition calculation process is terminated.

  On the other hand, when at least one of the injection amount Q6, the rail pressure Pcr6, and the flow velocity Vsw6 does not satisfy the restriction (step S306: NO), the process proceeds to step S308. In step S308, the boundary value (Qlim, Pcrlim, Vsmlim) of the control range of the downstream spray is determined as the control range. When step S308 is executed, the upstream spray control condition calculation processing ends.

  When the spray control conditions are determined in the process illustrated in FIG. 8 or FIG. 9, the ECU 100 selects the device corresponding to the control conditions, that is, the direct injection injector 370 if the injection amount Q, and the rail pressure Pcr. The high-pressure pump 350 is controlled, and the SCV 208 is controlled if the flow rate is Vsw. The control amount corresponding to the control condition is assumed to be mapped in advance and stored in the ROM.

  Here, with reference to FIG.10 and FIG.11, the position control of such a spray is demonstrated visually. FIG. 10 is a conceptual diagram of position control regarding the downstream spray, and FIG. 11 is a conceptual diagram of position control regarding the upstream spray. In these drawings, the same reference numerals are given to the same portions as those in the previous drawings, and the description thereof will be omitted as appropriate.

  10, FIG. 10 (a) shows a planar view positional relationship between the fuel injection valve 371 of the direct injection injector 370 and the glow plug 219, as in FIG.

  FIG. 10B shows the concept of position control when the actual downstream spray FSr is separated from the glow plug 219 (that is, the above-described distance b is too large). That is, in such a case, the spray angle θsp is expanded, and the downstream spray target position is set to the position of the illustrated target downstream spray Fstg (see the broken line).

  FIG. 10C shows the concept of position control when the actual downstream spray FSr is excessively overlapped with the glow plug 219 (that is, the above-described distance b is a negative value). That is, in such a case, the spray movement angle θsw is expanded by increasing the flow velocity Vsw, and the target position of the downstream spray is set to the position of the illustrated target downstream spray Fstg (see the broken line).

  On the other hand, in FIG. 11, FIG. 11A shows the positional relationship between the fuel injection valve 371 and the glow plug 219 in the position control of the spray (upstream spray) from the nozzle hole 3712 which is the upstream nozzle hole. It is.

  FIG. 11B shows the position control when the actual upstream spray FSr (solid line) is separated from the glow plug 219 (that is, the above-described distance b is too large) in such a positional relationship. The concept of is shown. That is, in such a case, the spray movement angle θsw is increased by increasing the flow velocity Vsw, and the target position of the upstream spray is set to the position of the illustrated target downstream spray Fstg (see the broken line).

  Returning to FIG. 6, when the control condition calculation process (step S200) ends, the ECU 100 determines whether or not the target spray is actually formed in the cylinder 202 (step S107). The spray position control in the control condition calculation process is a kind of F / F control, and the actual spray position is not reflected. Therefore, even if theoretically correct position control is performed, there is no guarantee that the actual spray maintains the desired position with respect to the glow plug 219.

  Therefore, in this embodiment, based on the drive current Igp of the glow plug 219, it is determined what positional relationship the spray (downstream spray or upstream spray) has on the glow plug 219.

  Here, the relationship between the drive current Igp and the spray position will be described with reference to FIG. FIG. 12 is a diagram illustrating time characteristics of the drive current Igp.

  In FIG. 12, the vertical axis represents the drive current Igp, and the horizontal axis represents time. Here, the drive current Igp changes as shown by the characteristics of the solid line, the broken line, and the thin broken line in accordance with the positional relationship between the glow plug 219 and the spray. The solid line is the time characteristic of the drive current Igp at the spray position A, the broken line is the time characteristic of the drive current Igp at the spray position B, and the thin broken line is the time characteristic of the drive current Igp at the spray position C.

  Here, each spray position will be described with reference to FIG. Here, FIG. 13 is a schematic bottom view plan view of the fuel injection valve 371 for explaining the spray positions exemplified in FIG. 12. In the figure, the same reference numerals are assigned to the same parts as those in FIG. 5, and the description thereof is omitted as appropriate.

  In FIG. 13, the spray positions A, B, and C correspond to FIGS. 13 (a), 13 (b), and 13 (c), respectively. That is, the spray position A is a position where the spray FS overlaps the glow plug 219, and the spray position B is a position where the spray FS is adjacent to the glow plug 219 (that is, targeted in this embodiment). The spray position C is a position where the spray FS does not overlap the glow plug 219 at all.

  Returning to FIG. 12, referring to FIG. 13, it can be seen that the drive current Igp of the glow plug 219 increases as the overlapping range of the glow plug 219 and the spray increases. Therefore, by continuously monitoring the drive current Igp and calculating the time change rate (time gradient) at a constant period, it is possible to clearly grasp where the actual spray is located with respect to the glow plug 219. be able to. In practice, the ECU 100 uses the time change rate of the drive current Igp in the time characteristics indicated by the broken line corresponding to the spray position B as a reference value, and if the time change rate is within a certain range including the reference value, the actual spraying is performed. Is determined to be maintained at the target position. If the time change rate exceeds the range, the actual spray is excessively overlapped with the glow plug 219. Conversely, if the time change rate is smaller than the range, the actual spray is too far from the glow plug 219. Will be.

  Returning to FIG. 6, if the target spray is formed (step S107: YES), the ECU 100 determines whether or not the cold start has ended (step S108), and if the cold start period has not ended. (Step S108: NO), the process waits until the cold start period ends. When the cold start period ends (step S108: YES), the glow plug 219 is controlled to be turned off (step S109), and the fuel injection control process ends.

  On the other hand, when it is determined in step S107 that the target spray is not formed (step S107: NO), the ECU 100 corrects the control condition calculated in step S200 (step S110). After correction, the process returns to step S107 again. That is, this correction is continued until it is determined that the target spray has been formed.

  For example, if the time change rate of the drive current Igp calculated from the time characteristic of the drive current Igp illustrated in FIG. 12 deviates to a side larger than a predetermined range, the ECU 100 causes the spray to grow higher than the target position. For example, the spray angle θsp is decreased or the spray movement angle θsw is increased or decreased (downstream spray or upstream spray) to the side where the overlap between the spray and the glow plug 219 is avoided. Depending on how).

  On the other hand, if the time change rate deviates to a side smaller than the predetermined range, it is assumed that the spray is farther from the glow plug 219 than the target position, so that the spray approaches the glow plug 219, for example, the spray angle. θsp is increased or the spray movement angle θsw is increased or decreased (depending on whether the spray is downstream or upstream).

  At this time, the positional relationship between the glow plug 219 and the spray and the time change rate of the drive current Igp (note that the time change rate is an example, and may be compared with, for example, a peak value) are one-to-one and many integrated. Correspond to many-to-one or many-to-many. Therefore, the deviation between the index value derived from the drive current Igp and the reference value may be roughly handled as the positional deviation between the glow plug 219 and the spray.

  As described above, according to the fuel injection control process according to the present embodiment, the kinematic viscosity of the fuel is reflected in the position control of the spray with respect to the glow plug 219. Therefore, not only when the static viscosity changes due to a change in the fuel type, but also when the density changes with the same type of fuel (for example, when the rail pressure Pcr changes), the fuel spray characteristics in the cylinder are accurately measured. Can be estimated. Furthermore, according to the present embodiment, it is found that the drive current Igp of the glow plug 219 changes depending on the positional relationship between the glow plug 219 and the spray, and the actual spray position in the cylinder is estimated from the time characteristics of the drive current Igp. It is possible to do. Furthermore, in addition to accurately determining the spray position control conditions reflecting the kinematic viscosity, the actual spray position is fed back to the correction of the position control conditions. Accordingly, it is possible to improve the ignitability of the fuel as much as possible during the cold start period when the glow plug 219 is in an operating state, and to realize extremely good startability.

  The present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification. Moreover, it is included in the technical scope of the present invention.

  The present invention is applicable to start control of a compression self-ignition internal combustion engine having a glow plug.

  DESCRIPTION OF SYMBOLS 10 ... Engine system, 100 ... ECU, 200 ... Engine, 202 ... Cylinder, 208 ... Swirl valve, 219 ... Glow plug, 300 ... Fuel injection system, 330 ... Feed pump, 350 ... High pressure pump, 360 ... Common rail, 370 ... Direct Injection injector, 371 ... fuel injection valve, 3711, 3712 ... injection hole, 380 ... fuel pressure sensor, 390 ... kinematic viscosity sensor.

Claims (4)

A swirl valve capable of controlling the flow rate of the intake swirl flow formed in the cylinder;
A glow plug capable of supplying thermal energy corresponding to a driving current to the gas in the cylinder;
Storage means capable of storing fuel at a fuel pressure equal to or higher than the in-cylinder pressure of the cylinder;
A high-pressure pump capable of controlling the fuel pressure;
A start-up control device for a compression self-ignition internal combustion engine comprising: injection means capable of injecting the stored fuel into a cylinder as a spray;
Specifying means for specifying the kinematic viscosity of the injected fuel;
The spraying means for defining spray characteristics related to the spray based on the specified kinematic viscosity so that the position of the spray with respect to the glow plug is a desired position during a period in which the glow plug is used. Determining means for determining a control condition of at least one of the high-pressure pump and the swirl valve;
Control means for controlling the at least one according to the determined control condition;
Estimating means for estimating the position of the spray with respect to the glow plug based on the characteristics of the driving current;
A starting control device comprising: a correction unit that corrects the determined control condition in accordance with a deviation between the estimated position and the desired position. 2. The start control device according to claim 1, wherein the estimation unit estimates the position based on a degree of change in the drive current in a period corresponding to the fuel injection period. The control condition of the injection means is the fuel injection amount,
The control condition of the high pressure pump is the fuel pressure,
The control condition of the swirl valve is the flow rate,
The determining means determines (1) the injection amount, (2) determines the injection amount and the fuel pressure when the determined injection amount does not satisfy the constraints, and (3) the determined injection. 3. The start control device according to claim 1, wherein the injection amount, the fuel pressure, and the flow velocity are determined when the amount and the fuel pressure do not satisfy constraints. The injection means includes a plurality of injection holes arranged circumferentially along the inner wall of the cylinder when the inside of the cylinder is viewed from the lower surface,
The determining means is: (1) Of the plurality of nozzle holes, a central axis of the nozzle hole when the inside of the cylinder is viewed from below is downstream with respect to the glow plug with respect to the direction of the swirl flow When the control condition is determined for the spray corresponding to the downstream nozzle hole closest to the side and the control condition determined for the spray corresponding to the downstream nozzle hole does not satisfy the constraint, (2) Among the plurality of nozzle holes, an upstream side injection nozzle whose center axis line when the inside of the cylinder is viewed from below is closest to the glow plug on the upstream side with respect to the direction of the swirl flow. The start control device according to any one of claims 1 to 3, wherein the control condition is determined for the spray corresponding to the hole.

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