JP5781855B2 - Spray characteristic estimation device - Google Patents

Description

  The present invention relates to fuel injection control in an internal combustion engine capable of injecting fuel into a cylinder, and more particularly to the technical field of a spray characteristic estimation device for estimating fuel spray characteristics.

  Regarding fuel injection control in an internal combustion engine, there is a combustion control device disclosed in Patent Document 1. According to this apparatus, in a multi-fuel internal combustion engine capable of using a plurality of fuels having different fuel properties, the ignitability and evaporability of the used fuel are detected from the fuel density, and the relationship between the ignitability and evaporability and the fuel pressure is shown. The fuel pressure of the fuel injected from the injector is determined based on the map data, and the fuel having higher ignitability and lower evaporability is injected with higher fuel pressure. For this reason, it is said that it is possible to achieve both improvement in fuel consumption and exhaust purification.

JP 2008-274905 A

  The atomization of fuel injected into the cylinder (fuel spray) is basically promoted as the fuel pressure increases, but as a qualitative tendency, the penetration force increases as the fuel pressure increases. The increase in penetration force is expressed as the amount of fuel spray adhering to the piston or cylinder inner wall without being sufficiently atomized, so-called wet (also referred to as cylinder wet or piston wet) (hereinafter referred to as “wet amount” as appropriate). ) Can be increased. Wet is hard to be combusted compared to atomized fuel spray because it is difficult to mix with the air sucked into the cylinder, and the increase in the amount causes an increase in unburned THC (Total Hydro Carbon). obtain. In view of this point, it is desirable that various control amounts of the in-cylinder injection unit including the fuel pressure are determined within a range that does not increase wetness or within a range where wetness does not occur.

  However, in the apparatus disclosed in the above-mentioned Patent Document 1, although ignitability and evaporability are considered, it is not considered what spray characteristics the fuel actually has in the cylinder, and the wet amount is sufficient. Cannot be controlled. Therefore, the effect of reducing exhaust emission may be hindered by unburned THC. That is, there is room for improvement in the conventional technology from the viewpoint of reducing exhaust emissions.

  This invention is made | formed in view of such a situation, and makes it a subject to provide an effective spray characteristic estimation apparatus in suppressing the increase in the wet quantity used as the factor of unburned THC production | generation.

  In order to solve the above-described problem, a spray characteristic estimation apparatus according to the present invention is a spray characteristic estimation apparatus that estimates the fuel spray characteristic in an internal combustion engine having in-cylinder injection means capable of injecting fuel into a cylinder. A kinematic viscosity specifying means for specifying the kinematic viscosity of the fuel, a gas state specifying means for specifying the gas state in the cylinder, and an estimation for estimating the spray characteristics based on the specified kinematic viscosity and gas state Means (claim 1).

  The internal combustion engine according to the present invention includes at least one in-cylinder injection unit such as a common rail in-cylinder injection device that can inject fuel into the cylinder, but as long as there is no limitation on the type of fuel used. . 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. The internal combustion engine according to the present invention may include a port injection unit capable of injecting fuel into the intake port in addition to the in-cylinder injection unit.

  The spray characteristic estimation apparatus according to the present invention is an apparatus capable of estimating at least the fuel spray characteristic in such an internal combustion engine (that is, for the purpose, injection using the spray characteristic estimated naturally). (It may include an element for executing control or the like), and as a preferable form, for example, one or a plurality of CPUs (Central Processing Units), MPUs (Micro Processing Units), various processors or various controllers are provided. In addition, a single or a plurality of ECUs (Electronic Controlled Units), a computer system, or the like may 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 fuel injection control device for an internal combustion engine 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. .

  “Fuel spray characteristics” according to the present invention is a physical quantity that defines the behavior or state of fuel spray in a cylinder corresponding to the wet amount in the cylinder, one-to-one, one-to-many, many-to-one, or many-to-many, It means a control amount, an index value, etc., and means, for example, penetration (spray reach or spray length), spray angle or particle size. For example, taking these as examples, it can be considered that the wet in the cylinder occurs in a range in which they are approximately equal to or greater than a certain threshold value.

  The fuel spray characteristics are controllable elements related to the in-cylinder injection means that can be determined to some extent in the operation control of the internal combustion engine, such as the fuel pressure and the injection amount, and the inherent elements of the in-cylinder injection means (in particular, the nozzle holes referred to as L / D) It is variable depending on inherent factors such as an index value obtained by dividing the length by the nozzle hole diameter. These can also be referred to in conventional fuel injection control.

  On the other hand, the fuel spray characteristics are also affected by the gas state in the cylinder. The gas state in the cylinder defined here is a gas state that can affect the behavior of the fuel 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). For example, if the in-cylinder temperature is low, the fuel is less likely to evaporate as a qualitative tendency, so that the penetration tends to be larger. If the in-cylinder density is higher, the penetration becomes less likely because the fuel spray is less likely to diffuse. Further, if the in-cylinder pressure is high, the fuel spray is difficult to diffuse as a qualitative tendency, so that the penetration tends to be small. In estimating the fuel spray characteristics, for example, it is desirable to consider such various gas states.

  On the other hand, the fuel spray characteristics are also affected by the viscosity (degree of viscosity) of the fuel injected from the in-cylinder injection means. Therefore, it is desirable to consider the viscosity of the fuel when estimating the fuel spray characteristics.

  By the way, the fuel spray injected from the in-cylinder injection means is a fluid. For this reason, it is difficult to estimate the fuel spray characteristics in the cylinder, which are dynamic characteristics, from the static viscosity (which is inherent to the fuel and is also called absolute viscosity). 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. . The spray characteristic estimation apparatus according to the present invention makes it possible to accurately estimate the spray characteristics as described below after finding such a point.

  That is, according to the spray characteristic estimation apparatus according to the present invention, the kinematic viscosity of the fuel is specified by the kinematic viscosity specifying means, and the gas state in the cylinder is specified by the gas state specifying means. The fuel spray characteristics are estimated by the estimating means based on the specified kinematic viscosity and gas state.

  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 kinematic viscosity specifying means is the kinematic viscosity defined in this way or the physical quantity, control quantity or Means index value.

  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 and particle size of the fuel spray change with respect to the kinematic viscosity. That is, the kinematic viscosity of the fuel as an index of the difficulty of movement of the actually injected fuel is an indispensable element for estimating the spray characteristics. According to the present invention, since the kinematic viscosity is referred to when the spray characteristics are estimated, it is possible to accurately estimate what spray characteristics the fuel spray exhibits in the cylinder. Accordingly, it is possible to accurately grasp whether and how much wet can occur in the cylinder, and realize fuel injection control that does not generate wet or reduces the wet amount. It becomes possible.

  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. Accordingly, the kinematic viscosity specifying means and the gas state specifying means may be detection means such as a sensor for detecting the kinematic viscosity and gas state of the fuel, respectively, or means for acquiring the detection result from this type of detection means provided separately. It may be a means for calculating according to a pre-determined algorithm or arithmetic expression. 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 addition, the practical aspect in which the estimation means according to the present invention estimates the spray characteristics is not limited as long as it is based on at least the specified kinematic viscosity and gas state. For example, the estimation means may use a preset arithmetic expression or algorithm that uses kinematic viscosity and gas state as reference elements for one or more spray characteristics to be estimated. Alternatively, the estimation means may include a control map having the kinematic viscosity and gas state as reference elements, which are stored in advance in an appropriate storage means for one or more spray characteristics to be estimated, which are set in advance from an experimental, empirical, or theoretical viewpoint. May be used. At this time, it is desirable that this kind of arithmetic expression and algorithm or control map is determined so as to reflect the influence of the controllable elements (fuel pressure and injection amount) and the inherent elements described above.

  In one aspect of the spray characteristic estimating apparatus according to the present invention, the kinematic viscosity specifying means is based on at least one of the pressure and flow rate of the fuel in the in-cylinder injection means and the operation amount of the in-cylinder injection means. The kinematic viscosity is specified (Claim 2).

  The kinematic viscosity of the fuel can be associated in advance with the behavior of the fuel in the in-cylinder injection unit such as the fuel pressure and the flow rate and the operation amount of the in-cylinder injection unit such as the needle lift amount of the fuel injection valve. For example, the relationship between fluctuations in fuel pressure and flow rate can vary depending on the kinematic viscosity of the fuel. Further, the operation amount of the in-cylinder injection means for obtaining a necessary flow rate and injection amount can also change depending on the kinematic viscosity of the fuel. Therefore, in the configuration in which the kinematic viscosity is specified from this type of reference element, the kinematic viscosity can be specified relatively easily.

  In another aspect of the spray characteristic estimating apparatus according to the present invention, the gas state includes at least one of a temperature, a density, and a pressure of the gas in the cylinder (claim 3).

  According to this aspect, since the spray characteristic is estimated based on at least one of the in-cylinder gas temperature, the in-cylinder density, and the in-cylinder pressure that significantly affects the spray characteristic in the gas state, the spray characteristic is It is possible to estimate with relatively high accuracy.

  In another aspect of the spray characteristic estimation apparatus according to the present invention, the spray characteristic includes at least one of penetration, particle size, and spray angle of the fuel.

  According to this aspect, since at least one of the penetration, the particle size, and the spray angle that can significantly affect the presence or absence of wet and the wet amount is estimated, the fuel injection control based on the estimation result is performed. In this case, the wet amount can be controlled with relatively high accuracy.

  In another aspect of the spray characteristic estimation apparatus according to the present invention, the spray characteristic estimation apparatus further includes injection control means for controlling the in-cylinder injection means so that the wet amount decreases based on the estimated spray characteristic. .

  According to this aspect, since the injection control means controls the in-cylinder injection means so that the wet amount decreases based on the estimated spray characteristics, it becomes possible to avoid or suppress the occurrence of unburned THC, It becomes possible to maintain the exhaust emission well.

  In this aspect, the injection control unit may control at least one of the fuel injection timing, the injection amount, the number of injections, and the injection pressure in the in-cylinder injection unit.

  Injection timing, injection quantity, number of injections, and injection pressure (In-cylinder injection means using a high-pressure pump and high-pressure delivery, the injection pressure is treated synonymously with the pressure of fuel stored in the high-pressure delivery, that is, fuel pressure. Is good as a control amount of the in-cylinder injection means and has good controllability. Therefore, in this case, it is possible to relatively easily control the wet amount in the cylinder.

  In another aspect of the spray characteristic estimation device according to the present invention, the internal combustion engine includes an EGR device that recirculates a part of the exhaust gas as EGR gas to the intake system, and the spray characteristic estimation device includes the estimated spray characteristic. (Embodiment 7) is further provided with an EGR control means for controlling the EGR device so that the wet amount is reduced based on the above.

  According to this aspect, by changing the temperature and density of fresh air sucked into the cylinder by the action of the EGR control means, the gas state in the cylinder, particularly the in-cylinder temperature and in-cylinder density, can be controlled. Can be changed. Therefore, the spray characteristics in the cylinder can be controlled, and it is possible to avoid the occurrence of wetness or to suppress the wet amount.

  The operation of the EGR control means is not alternative to the operation of the above injection control means, and both can be suitably used together. However, according to the EGR control means, for example, the controllable range of the in-cylinder injection means This is useful in practice because the amount of wet can be reduced as much as possible in the case where the width is narrow (there are many restrictions).

  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 a first 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. 2 is a flowchart of a fuel injection control process executed by an ECU in the engine system of FIG. FIG. 6 is a conceptual diagram of a spray characteristic estimation map used for estimating spray characteristics in the fuel injection control process of FIG. 5. It is a figure showing the relationship between evaporation temperature and kinematic viscosity. It is a figure explaining the concept of the injection control in the fuel-injection control process of FIG. It is a flowchart of the fuel-injection control process which concerns on 2nd Embodiment of this invention.

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

<First Embodiment>
<Configuration of Embodiment>
First, the configuration of the engine system 10 according to the first 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 “kinematic viscosity specifying means”, “gas state specifying means”, “estimating means”, and “injection control 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 rate 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.

  The EGR device 400 includes an EGR pipe 410, an EGR cooler 420, an EGR valve 430, a bypass pipe 440, and a bypass control valve 450.

  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 is installed in the EGR pipe 410 and cools a relatively high-temperature EGR gas immediately after exhaust flowing into the cooler 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 valve opening Aegr that is the opening of the EGR valve 430 can be controlled by the ECU 100. Yes. The “opening degree” means the degree of opening of the valve, and the EGR valve 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.

  The bypass pipe 440 is a metal tubular member that communicates the upstream side (exhaust port side) and the downstream side (intake port side) of the EGR cooler 420 in the EGR pipe 410 so as to bypass the EGR cooler 420.

  The bypass control valve 450 is an electromagnetically controlled switching valve provided at a joint portion between the EGR pipe 410 and the bypass pipe 440 on the upstream side of the EGR cooler 420. The bypass control valve 450 can change the flow rate ratio between the EGR gas passing through the EGR cooler 420 and the EGR gas bypassing the EGR cooler 420 via the bypass pipe 450 in multiple stages according to the valve opening degree. It can be configured. The bypass control valve 450 is electrically connected to the ECU 100, and the valve opening degree is controlled by the ECU 100.

  In the EGR device 400, a part of the exhaust discharged to the exhaust port 213 depends on 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 valve opening Aegr. It is circulated to the intake port 209 as EGR gas.

  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 fuel 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 fuel pressure Php (Php> Pfd), which is the pressure of the high-pressure fuel stored in the common rail 360, is detected by the fuel pressure sensor 380. The fuel pressure sensor 380 is electrically connected to the ECU 100, and the detected fuel pressure Php is referred to by the ECU 100 at a constant or indefinite period. The ECU 100 can maintain the fuel pressure Php 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 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 “in-cylinder injection unit” according to the present invention in the narrow sense. In a broad sense, the entire fuel injection system 300 is also an example of “in-cylinder injection means” according to the present invention.

  The direct injection injector 370 is provided for each cylinder 202, and the fuel injection valve of each direct injection injector 370 is exposed inside each cylinder 202 as described above. The direct injection 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 fuel pressure Php into the cylinder 202 as fuel 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.

  Here, the configuration of the direct injection injector 370 will be supplemented.

  The direct injection injector 370 includes an electromagnetic valve that operates based on a command supplied from the ECU 100, and a nozzle (all not shown) that injects fuel when the electromagnetic valve is energized. 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.

  In the present embodiment, the injection pressure Pinj of the fuel injected from the injection hole of the direct injection injector 370 and the fuel pressure Php are treated as synonymous.

<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. 5 is a flowchart of the fuel injection control process.

  In FIG. 5, 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 S10). Step S10 is an example of the operation of the “kinematic viscosity specifying unit” according to the present invention.

  Here, the kinematic viscosity of the high-pressure fuel is directly detected by the kinematic viscosity sensor 390, but of course, the practical aspect that can be taken by the kinematic viscosity specifying 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 fuel pressure Php and the mass of the common rail 360 is obtained experimentally, empirically, or theoretically in advance, the fuel density Df can be obtained based on the fuel pressure Php detected by the fuel pressure sensor 380. It is.

  Alternatively, the kinematic viscosity Vk is obtained from the needle lift amount when the means for detecting the needle lift amount (an example of the “operation amount” according to the present invention) of the direct injection injector 370 is installed. You can also. 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 fuel pressure Php in the common rail 360. That is, when the time characteristic of the detected fuel pressure Php 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 fuel pressure Php.

  When the kinematic viscosity Vk is determined by any method, the ECU 100 reads the internal state of the cylinder 202 (hereinafter, referred to as “in-cylinder state” as appropriate) (step S20). Step S20 is an example of the operation of the “gas state specifying means” according to the present invention.

  In step S20, the in-cylinder temperature Tcy, the in-cylinder pressure Pcy, and the in-cylinder density Dcy (gas density in the cylinder 202) are read as the in-cylinder state. The in-cylinder temperature Tcy and the in-cylinder pressure Pcy are read from sensor values acquired from the corresponding sensors. On the other hand, the in-cylinder density Dcy is calculated by the sub processor of the ECU 100 based on the in-cylinder volume, the intake amount (the amount of gas sucked into the cylinder 202), the EGR rate (the ratio of the EGR gas amount to the new air amount), and the like. In step S20, the calculated value is read. In the engine 200, the piston 203 continuously moves up and down, and the in-cylinder density periodically changes. This in-cylinder density Dcy is used for estimating the fuel spray characteristics as will be described later. Therefore, it basically means the in-cylinder density during the period corresponding to the fuel injection timing.

  When the kinematic viscosity Vk and the in-cylinder state are obtained, the ECU 100 estimates the spray characteristics based on these (step S30). Step S30 is an example of the operation of the “estimating means” according to the present invention.

  The spray characteristic of the fuel spray according to step S30 means a physical quantity, a control amount, or an index value relating to the behavior of the fuel spray inside the cylinder, which is defined as defining the wet generation state in the cylinder 202. In particular, the fuel spray penetration PN, the particle size R, and the spray angle Ainj are estimated as the spray characteristics. The penetration PN is the distance from the injection hole of the direct injection injector 370 to the spray tip. The particle size R is the particle size of the fuel particles in the fuel spray. Further, the spray angle Ainj is an angle formed by a tangent drawn from the nozzle hole to the maximum width portion (left and right) of the fuel spray that diffuses in a fan shape when viewed from above.

  These are defined as a function of a plurality of elements as shown in the following equations (2) to (4). In the following formula, “L / D” is a value obtained by dividing the injection hole length of the direct injection injector 370 by the injection hole diameter, and is a value inherent to the direct injection injector 370.

PN = Func1 (fuel pressure Php, L / D, injection amount Qinj, evaporation temperature Tvp, particle size R, cylinder temperature Tcy, cylinder density Dcy) (2)
R = Func2 (kinematic viscosity Vk, fuel pressure Php, L / D, injection amount Qinj) (3)
Ainj = Func3 (kinematic viscosity Vk, fuel pressure Php, L / D, injection amount Qinj) (4)

  Funci (i = 1, 2, 3) in each of the above expressions means a function of an element described in parentheses at the subsequent stage. These functions may be determined experimentally, empirically or theoretically in advance, and may be given as arithmetic expressions or derivation algorithms. In this embodiment, these functions are mapped for each spray characteristic. That is, the ECU 100 stores a spray characteristic estimation map that uses the above-mentioned elements as parameters for each spray characteristic. When the ECU 100 estimates the spray characteristics, the spray characteristic estimation map for each spray characteristic (that is, penetration) is stored. The estimation map, the particle size estimation map, and the spray angle estimation map) are referred to.

  Here, the spray characteristic estimation map will be described with reference to FIG. FIG. 6 is a conceptual diagram of the spray characteristic estimation map.

  In FIG. 6, FIGS. 6 (a), 6 (b), and 6 (c) show the concept of the penetration estimation map, the particle size estimation map, and the spray angle estimation map, respectively.

  In FIG. 6A, the diagram on the left side of FIG. 6 shows a change characteristic of the penetration PN with respect to the kinematic viscosity Vk when the fuel pressure Php is changed between Phpa and Phpb (Phpa> Phpb) at a certain injection amount Qinj. is there. The change characteristic corresponding to the fuel pressure Phpa is represented as L_phpa1 (see solid line) in the figure, and the change characteristic corresponding to the fuel pressure Phpb is represented as L_phpb1 (see broken line) in the figure. Further, the diagram on the right side in the figure shows the change characteristics of the penetration PN with respect to the kinematic viscosity Vk when the injection amount Qinj is changed between Qinja and Qinjb (Qinja> Qinjb) at a certain fuel pressure Php. The change characteristic corresponding to the injection amount Qinja is represented as L_Qinja1 (see the solid line) in the drawing, and the change characteristic corresponding to the injection amount Qinjb is represented as L_Qinjb1 (see the broken line) in the drawing.

  As shown in the figure, the penetration PN as one spray characteristic increases on the other hand as the fuel pressure increases, and generally decreases as the kinematic viscosity increases. Further, the sensitivity of the penetration with respect to the fuel pressure generally increases as the kinematic viscosity becomes low, and when the kinematic viscosity Vk exceeds a certain threshold, the influence of the fuel pressure is almost eliminated. On the other hand, the penetration PN increases as the injection amount increases, and generally decreases as the high kinematic viscosity increases. Further, the sensitivity of the penetration with respect to the injection amount is almost constant regardless of the kinematic viscosity.

  In the penetration estimation map, the relationship illustrated in FIG. 6A is digitized and stored. At this time, it is needless to say that the fuel pressure Php and the injection amount Qinj are defined in more stages than the two illustrated. As can be seen from the above equation (2), the penetration PN is not limited to the fuel pressure Php (which is treated as synonymous with the injection pressure Qinj as described above) and the injection amount Qinj. It is a function of the internal temperature Tcy and the in-cylinder density Dcy. Here, for the purpose of preventing the explanation from becoming complicated, the change in the penetration PN for each of them will not be shown, but the relationship illustrated in FIG. 6A is naturally defined for each of these other parameters. Yes.

  By the way, referring to the above equation (2) that defines the penetration PN, the kinematic viscosity Vk is not included as a parameter of the function that defines the penetration, but the penetration PN is a function of the kinematic viscosity Vk. This is because the evaporation temperature Tvp included in the equation (2) is a function of the kinematic viscosity Vk. The evaporation temperature Tvp is an index value of the ease of vaporization of fuel spray. Here, the relationship between the evaporation temperature Tvp and the kinematic viscosity Vk will be described with reference to FIG. FIG. 7 is a diagram showing the relationship between the evaporation temperature Tvp and the kinematic viscosity Vk.

  As shown in FIG. 7, the fuel evaporation temperature Tvp has a substantially linear characteristic with respect to the kinematic viscosity Vk, and tends to become lower (higher) as the kinematic viscosity Tvk becomes lower (higher). Thus, since the evaporation temperature changes depending on the kinematic viscosity Vk, the penetration PN also changes according to the kinematic viscosity Vk.

  In FIG. 6B, the diagram on the left side of FIG. 6B shows the change characteristic of the particle size R with respect to the kinematic viscosity Vk when the fuel pressure Php is changed between Phpa and Phpb (Phpa> Phpb) at a certain injection amount Qinj. It is. The change characteristic corresponding to the fuel pressure Phpa is represented as L_phpa2 (see the solid line) in the figure, and the change characteristic corresponding to the fuel pressure Phpb is represented as L_phpb2 (see the broken line) in the figure. Further, the diagram on the right side in the figure shows a change characteristic of the particle diameter R with respect to the kinematic viscosity Vk when the injection amount Qinj is changed between Qinja and Qinjb (Qinja> Qinjb) at a certain fuel pressure Php. The change characteristic corresponding to the injection amount Qinja is represented as L_Qinja2 (see the solid line) in the figure, and the change characteristic corresponding to the injection amount Qinjb is represented as L_Qinjb2 (see the broken line) in the figure.

  As shown in the figure, the particle size R as a spray characteristic is smaller as the fuel pressure is higher and is generally larger as the kinematic viscosity is higher. Further, the sensitivity of the particle size R to the fuel pressure hardly depends on the kinematic viscosity. On the other hand, strictly speaking, the particle size R tends to decrease as the injection amount increases, but practically hardly changes with respect to the injection amount, and generally increases as the kinematic viscosity increases. Further, the sensitivity of the particle diameter R with respect to the injection amount hardly depends on the kinematic viscosity.

  In the particle size estimation map, the relationship illustrated in FIG. 6B is digitized and stored. At this time, it is needless to say that the fuel pressure Php and the injection amount Qinj are defined in more stages than the two illustrated.

  In FIG. 6C, the diagram on the left side of FIG. 6 shows the change characteristic of the spray angle Ainj with respect to the kinematic viscosity Vk when the fuel pressure Php is changed between Phpa and Phpb (Phpa> Phpb) at a certain injection amount Qinj. It is. The change characteristic corresponding to the fuel pressure Phpa is represented as L_phpa3 (see the solid line) in the figure, and the change characteristic corresponding to the fuel pressure Phpb is represented as L_phpb3 (see the broken line) in the figure. Further, the diagram on the right side in the figure shows the change characteristic of the spray angle Ainj with respect to the kinematic viscosity Vk when the injection amount Qinj is changed between Qinja and Qinjb (Qinja> Qinjb) at a certain fuel pressure Php. The change characteristic corresponding to the injection amount Qinja is represented as L_Qinja3 (see the solid line) in the figure, and the change characteristic corresponding to the injection amount Qinjb is represented as L_Qinjb3 (see the broken line) in the figure.

  As shown in the figure, the spray angle Ainj as one spray characteristic increases on the other hand as the fuel pressure increases, and generally decreases as the kinematic viscosity increases. However, the change with respect to the kinematic viscosity is larger in the low to medium kinematic viscosity region and almost level in the medium to high kinematic viscosity region. Moreover, the sensitivity of the spray angle Ainj with respect to the fuel pressure hardly depends on the kinematic viscosity. On the other hand, the spray angle Ainj increases as the injection amount increases, and generally decreases as the high kinematic viscosity increases. Further, the sensitivity of the spray angle Ainj with respect to the injection amount hardly depends on the kinematic viscosity.

  In the spray angle estimation map, the relationship illustrated in FIG. 6C is digitized and stored. At this time, it is needless to say that the fuel pressure Php and the injection amount Qinj are defined in more stages than the two illustrated.

  Returning to FIG. 5, when the spray characteristics of the fuel spray are estimated, the ECU 100 determines the injection conditions based on the spray characteristics (step S40), and the high-pressure pump 350 or the direct injection injector 370 is changed according to the determined injection conditions. Drive control is performed (step S50). Steps S40 and S50 are an example of the operation of the “control means” according to the present invention. When step S50 is executed, the process returns to step S10, and a series of processes is repeated.

  Here, the determination of the injection condition in step S40 will be described with reference to FIG. FIG. 8 is a diagram for explaining the concept of the injection condition determination process.

  8, (a), (b), and (c) show the relationship between the penetration PN and the kinematic viscosity Vk, the relationship between the particle size R and the kinematic viscosity Vk, and the spray angle Ainj and the kinematics, respectively. It is the figure which represented the relationship with the viscosity Vk notionally.

  In FIG. 8A, a region where the penetration PN is larger than the threshold value PN0 is a wet region WET where wetness occurs in the cylinder 202. The threshold value PN0 is unchanged with respect to the kinematic viscosity Vk. Here, if the operating point (one coordinate point on the coordinate plane) corresponding to the penetration PN estimated in step S30 is the illustrated operating point mP1 (black circle), the penetration PN becomes the value of the wet region WET as it is. Therefore, there is a possibility that wet will occur and unburned THC will increase. Therefore, in step S40, for example, the illustrated operating point mP2 (white circle) is determined as a control target (broken line arrow), and the injection conditions for realizing this control target are determined.

  In FIG. 8B, the region where the particle size R is larger than the threshold value R0 is a wet region WET where wet occurs. The threshold value R0 is unchanged with respect to the kinematic viscosity Vk. Here, if the operating point (one coordinate point on the coordinate plane) corresponding to the particle size R estimated in step S30 is the illustrated operating point mR1 (black circle), the particle size R is the value of the wet region WET as it is. Therefore, there is a possibility that wet will occur and unburned THC will increase. Therefore, in step S40, for example, the illustrated operating point mR2 (white circle) is determined as a control target (broken line arrow), and the injection conditions for realizing this control target are determined.

  In FIG. 8C, a region where the spray angle Ainj is larger than the threshold value Ainj0 is a wet region WET where wetness occurs. The threshold value Ainj0 is invariant with respect to the kinematic viscosity Vk. Here, if the operation point (one coordinate point on the coordinate plane) corresponding to the spray angle Ainj estimated in step S30 is the illustrated operation point mA1 (black circle), the spray angle Ainj is the value of the wet region WET as it is. Therefore, there is a possibility that wet will occur and unburned THC will increase. Therefore, in step S40, for example, the illustrated operating point mA2 (white circle) is determined as a control target (broken line arrow), and the injection conditions for realizing this control target are determined.

  Here, the injection condition for reaching the control target is a control condition for the direct injection injector 370 or the high-pressure pump 350. In this embodiment, at least one of the injection timing, the injection amount Qinj, the number of injections, and the fuel pressure Php is at least one. Is set. The influence of the injection amount Qinj and the fuel pressure Php on the spray characteristics has been described above. However, since the number of injections also reduces the injection amount per injection, the same effect as reducing the injection amount Qinj can be obtained. Further, since the combustion state of the air-fuel mixture changes when the injection timing changes, the in-cylinder temperature Tcy changes. Since the in-cylinder temperature Tcy affects the spray characteristics, the control of the injection timing is also effective for avoiding the generation of wet or reducing the wet amount.

  As described above, according to the present embodiment, it is possible to accurately grasp the fuel spray characteristics that have a high correlation with the occurrence of wetness or the wet amount in the cylinder 202 based on the kinematic viscosity of the fuel. Therefore, it is possible to suppress the generation of wet or reduce the wet amount as much as possible and suppress the discharge of unburned THC as much as possible. Referring to FIG. 6, it is clear that the spray characteristics estimated when the kinematic viscosity of the fuel is not taken into account are very ambiguous, and even if the need to reduce wetness can be conceived, the spray characteristics It is easily inferred that excessive or deficient control may occur. That is, the fuel injection control process according to the present embodiment is clearly advantageous in that it has a technical idea that kinematic viscosity is used for estimation of spray characteristics.

Second Embodiment
Next, the fuel injection control process according to the second embodiment of the present invention will be described with reference to FIG. FIG. 9 is a flowchart of the fuel injection control process according to the second embodiment. In addition, in the same figure, the same code | symbol is attached | subjected to the location which overlaps with FIG.

  In FIG. 9, when the estimation of the spray characteristics ends (step S30), the ECU 100 determines the control conditions of the EGR device 400 (step S41), and the EGR device 400 (particularly, the switching control valve 450) according to the determined control conditions. Is controlled (step S51). That is, in the second embodiment, the ECU 100 functions as an example of “EGR control means” according to the present invention.

  As described in the first embodiment, the penetration PN among the spray characteristics is variable according to the in-cylinder temperature Tcy and the in-cylinder density Dcy of the cylinder 202. The in-cylinder temperature Tcy and the in-cylinder density Dcy change the flow rate ratio between the EGR gas flowing into the EGR cooler 420 and the EGR gas bypassing the EGR cooler 420 by driving control of the switching control valve 450 in the EGR device 400. It can be changed by changing the temperature and density of fresh air flowing into the cylinder 202.

  Qualitatively, since the cooling of the EGR gas proceeds as the ratio of the EGR gas flowing into the EGR cooler 420 increases, the in-cylinder temperature Tcy of the cylinder 202 decreases. Further, since the density of the EGR gas increases as the ratio of the EGR gas flowing into the EGR cooler 420 increases, the in-cylinder density Dcy of the cylinder 202 increases.

  Therefore, when the spray characteristic that violates the constraint on wet generation (that is, exceeds the threshold) is penetration PN, ECU 100 uses the penetration estimation map to make penetration PN less than threshold PN0, or penetration PN. The in-cylinder temperature Tcy and the in-cylinder density Dcy that can reduce the flow rate as much as possible are calculated and replaced with the control amount of the switching control valve 450, that is, the valve opening degree of the switching control valve 450, which correlates with the flow rate ratio. The correspondence between the two for the replacement process is given experimentally, empirically or theoretically in advance.

  As described above, according to the present embodiment, the suppression of wet generation or the reduction of the wet amount is achieved by the drive control of the EGR device 400 instead of the drive control of the direct injection injector 370 or the high-pressure pump 350. Therefore, the same effect as the first embodiment is achieved. Further, for example, even when there are restrictions or restrictions on the operation of the direct injection injector 370, it is possible to suppress the generation of wet or reduce the wet amount as much as possible.

  In changing the in-cylinder temperature Tcy and the in-cylinder density Dcy, the EGR valve 430 may be controlled instead of the switching control valve 450. However, when the temperature and density of fresh air are changed by controlling the EGR valve 430 (that is, controlling the EGR valve opening Aegr), the EGR rate also naturally changes due to the change in the EGR valve opening Aegr. Combustion conditions can change significantly. In view of this point, it is desirable to control the flow rate ratio by controlling the valve opening of the switching control valve 450 as described above.

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

  The present invention is applicable to fuel injection control of an internal combustion engine provided with in-cylinder injection means.

  DESCRIPTION OF SYMBOLS 10 ... Engine system, 100 ... ECU, 200 ... Engine, 202 ... Cylinder, 300 ... Fuel injection system, 330 ... Feed pump, 350 ... High pressure pump, 360 ... Common rail, 370 ... Direct injection injector, 380 ... Fuel pressure sensor, 390 ... Kinematic viscosity sensor, 400 ... EGR device, 420 ... EGR cooler, 440 ... Bypass pipe, 450 ... Switching control valve.

Claims (6)

A spray characteristic estimation device for estimating a fuel spray characteristic in an internal combustion engine provided with an in-cylinder injection unit capable of injecting fuel into a cylinder,
Kinematic viscosity specifying means for specifying the kinematic viscosity of the fuel;
Gas state specifying means for specifying a gas state in the cylinder;
A spray characteristic estimation device comprising: an estimation unit configured to estimate at least one of the penetration and the particle size of the fuel based on the specified kinematic viscosity and gas state. The kinematic viscosity specifying means specifies the kinematic viscosity based on at least one of the pressure and flow rate of the fuel in the in-cylinder injection means and the operation amount of the in-cylinder injection means. The spray characteristic estimation apparatus described in 1. The spray characteristic estimation device according to claim 1, wherein the gas state includes at least one of a temperature, a density, and a pressure of the gas in the cylinder. Any of claims 1 to 3, further comprising a jetting controller that controls the in-cylinder injection means so that the wet weight is reduced based on at least one of the estimated penetration and particle size The spray characteristic estimation apparatus according to one item. The spray characteristic estimation apparatus according to claim 4 , wherein the injection control unit controls at least one of an injection timing, an injection amount, an injection count, and an injection pressure of the fuel in the in-cylinder injection unit. The internal combustion engine includes an EGR device that recirculates a part of the exhaust gas as EGR gas to the intake system,
The spray characteristic estimation device further comprises an EGR control means for controlling the EGR device so that a wet amount decreases based on at least one of the estimated penetration and particle size. To 4. The spray characteristic estimation device according to any one of claims 1 to 3 .

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