Fuel injection control device

Abstract

Fuel injection control device (40) configured to control a fuel injection system (1), the fuel injection system comprising a direct injection fuel injector (30) configured to inject high-pressure fuel directly into a combustion chamber (21) of an internal combustion engine (10) in a collector (32), the fuel injection control device comprising: a selection unit (43) which is configured such that this an injection mode of fuel to be injected in a compression stroke of the internal combustion engine, between a soot reduction mode in which fuel is prevented from remaining at a tip end face of a valve body (51) with respect to a seat section (56) at the fuel injector in order to reduce soot, and another injection mode which differs from the soot reduction mode, based on a predetermined switching condition, and selects the injection mode; and an injection control unit (44) which is configured to perform fuel injection which is set in the compression stroke of the internal combustion engine, based on the injection mode selected by the selection unit, wherein The soot reduction mode is set to increase the opening and closing speed of the fuel injector so that it is faster than that in any other injection mode when fuel injection is carried out during the compression stroke of the internal combustion engine in order to reduce the amount of soot produced.

Description

Technical field

[0001] The present disclosure relates to a fuel injection control device configured for injecting fuel into an internal combustion engine. General state of the art

[0002] A fuel injection control device controls the injection state of fuel injected by a fuel injector in an internal combustion engine to promote combustion efficiency of the internal combustion engine and to reduce harmful components, such as particulate matter (PM) and NOx, contained in the exhaust gas from the internal combustion engine.

[0003] For example, deposits can accumulate around the injection holes of a fuel injector. These deposits cause the fuel jet to disperse, leading to a reduction in the combustion efficiency of the internal combustion engine and a decrease in torque. To suppress fuel jet dispersal, patent literature 1 describes a prediction of the deposit amount, and if the deposit amount exceeds a predetermined quantity, the fuel injection pressure is increased to remove the deposit.

[0004] DE 11 2015 005 997 T5 describes a fuel injection valve control device that controls a fuel injection valve which injects fuel into a combustion chamber, has an operating condition calculation section which calculates a fuel injection condition of the fuel injection valve based on a crank angle which is detected by a crank angle sensor which detects a crank angle of a machine, a current curve setting section which sets a current curve of a current which supplies the fuel injection valve based on the fuel injection condition which is calculated by the operating condition calculation section, and so on.The current curve adjustment section sets the current curve to adjust the time-dependent change of a needle lift current provided in the fuel injector to be equal to or less than a predetermined reference value when a fuel injection start time is equal to or greater than 180 degrees BTDC. The current curve adjustment section also sets the current curve to adjust the time-dependent change of the needle lift current to be greater than the predetermined reference value when the fuel injection start time is less than 180 degrees BTDC.

[0005] EP 3 287 626 A1 discloses an engine control device that controls a direct-injection gasoline engine equipped with a fuel injector that injects fuel directly into a cylinder and a spark plug configured to ignite a gas mixture in the cylinder. During a compression stroke of the fuel injection timing, the engine control device performs a catalyst warm-up procedure to retard the ignition timing when necessary to warm up an exhaust gas purification catalyst inserted into an exhaust manifold. Furthermore, the engine control device increases the valve overlap period as the piston crown surface temperature increases during the catalyst warm-up procedure.

[0006] DE 11 2016 004 815 T5 describes a particle detection device. This device estimates the volume of water inside an outlet using estimation sections. If the estimated water volume is greater than a water discharge threshold, a section is heated by a heater through the first temperature range control device within a temperature range that prevents water-induced cracking, regardless of the volume of water droplets. If the estimated water volume is less than a water discharge threshold, the water discharge determination section determines that the water discharge of the outlet is complete.If it is estimated that water drainage is complete, the element section is additionally heated by a second temperature control device at a lower temperature than the starting temperature for particle combustion, and to repel water adhering to the element section for a predetermined period of time within a water repulsion temperature range. Literature on the state of the art, patent literature

[0007] Patent Literature 1: JP 2017-129046 A Summary of the invention

[0008] One factor that impairs the performance of an internal combustion engine is the formation of soot in the combustion chamber. When soot is produced, harmful components, such as particulate matter (PM), contained in the engine's exhaust gas cannot be sufficiently reduced. Deposits accumulating on a fuel injector also contribute to soot formation. Furthermore, when a fuel injector remains closed after injection, some fuel can remain inside the injector's reservoir and adhere to the nozzle tip. This fuel is then exposed to the gas in the combustion chamber, causing soot to form.

[0009] The method described in patent literature 1 for increasing fuel injection pressure is a method for removing a deposit and does not address the suppression of soot formation resulting from fuel remaining in the fuel injector. In particular, when fuel is injected during the compression stroke of an internal combustion engine, the time available for vaporizing any fuel remaining at the tip of the fuel injector is short compared to when fuel is injected during the intake stroke. Therefore, more soot is generated from the remaining fuel. Furthermore, especially when the time between fuel injection and ignition is short, if the injected fuel pressure is set excessively high, the pulse of the injected fuel will be high. Consequently, the fuel may barely pass the spark plug.Furthermore, the fuel flow is poorly coordinated with the airflow, and therefore, between fuel injection and ignition, the fuel barely forms an air-fuel mixture around the spark plug. This raises concerns that the desired combustion of the fuel may be prevented.

[0010] In view of the foregoing, it is an object of the present disclosure to provide a fuel injection control device configured to suppress the generation of soot in a fuel injection system that injects fuel mainly during a compression stroke of an internal combustion engine.

[0011] The present disclosure provides a fuel injection control device for controlling a fuel injection system. The fuel injection system comprises: a collector for storing high-pressure fuel; and a direct-injection fuel injector for injecting high-pressure fuel directly into the combustion chamber of an internal combustion engine from the collector.This fuel injection control device comprises: a selection unit configured to switch between a soot reduction mode, in which fuel is prevented from remaining at a tip end face of a valve body with respect to a seat section at the fuel injector in order to reduce soot, and another injection mode different from the soot reduction mode, based on a predetermined switching condition and to select the injection mode; and an injection control unit configured to perform a fuel injection set in a compression stroke of the internal combustion engine based on the injection mode selected by the selection unit.

[0012] According to the fuel injection control device of the present disclosure, the selection unit switches the fuel injection mode of the fuel to be injected during the compression stroke of the internal combustion engine between the soot reduction mode and another injection mode based on the predetermined switching condition and selects the fuel injection mode. The injection control unit performs a fuel injection during the compression stroke of the internal combustion engine based on the injection mode selected by the selection unit. Therefore, the configuration allows fuel injection in soot reduction mode to be performed as needed, thereby suppressing soot production.Furthermore, the soot reduction mode corresponds to an injection mode configured to prevent fuel from remaining on the tip end face relative to the seat section of the fuel injector body, thereby reducing soot. This configuration effectively suppresses wet fuel adhesion, which tends to occur during fuel injection during the compression stroke of the internal combustion engine. Consequently, this configuration suppresses the formation of PM and similar substances due to soot buildup, while still allowing fuel injection to occur during the compression stroke. Brief description of the illustrations

[0013] The foregoing and further tasks, features, and advantages of the present disclosure will become more apparent from the following detailed description, which is carried out with reference to the accompanying illustrations. The illustrations show: Fig. 1 a schematic representation showing a fuel injection system according to one embodiment; Fig. 2 a sectional view showing a fuel injector of the fuel injection system of Fig. 1 shows; Fig. 3 a system block diagram showing an ECU corresponding to a fuel injection control device according to the embodiment; Fig. 4 a view showing a relationship between a time interval from an injection end time to an ignition time, a fuel pressure at the time of injection and a quantity of soot produced; Fig. 5 a view which shows a relationship between the amount of soot produced and the amount of PM in the exhaust gas; Fig. 6 a view showing a relationship between the amount of soot produced and the amount of HC in the exhaust gas; Fig. 7 a view showing temporal changes in PM quantity, HC quantity or amount of soot produced in the exhaust gas before and after switching an injection mode; Fig. 8 a view which shows a relationship between the time interval from the end of the injection time to the ignition time, an intensity of an airflow in a combustion chamber at the time of an injection and an increase and decrease in a deposit quantity; Fig. 9 a view showing an example of injection patterns in a normal mode or a soot reduction mode; and Fig. 10 a flow diagram showing a fuel injection control according to the embodiment. Description of embodiments

[0014] As in Fig. As shown in Figure 1, a fuel injection system 1 corresponds to a system configured such that high-pressure fuel, stored in a collector or reservoir 32, is injected by a direct-injection fuel injector 30 into a combustion chamber 21 of an internal combustion engine 10. The internal combustion engine 10 is a multi-cylinder engine of the cylinder or direct-injection type, which implements an intake stroke, a compression stroke, a combustion or power stroke, and an exhaust stroke as a combustion cycle. The collector 32 is a delivery pipe and stores high-pressure fuel, which is supplied under pressure by a high-pressure pump 33. A low-pressure pump 34 supplies fuel from a fuel tank (not shown) to the high-pressure pump 33. A fuel pressure sensor 37 is provided to detect the pressure (fuel pressure) of the fuel in the collector 32.

[0015] An intake air flow rate sensor 13, which serves to detect the flow rate of intake air, and an intake air temperature sensor 14 are provided on the upstream side of an intake manifold 12 of the internal combustion engine 10. A throttle valve or throttle valve 16, the opening of which is adjusted using a motor 15, and a throttle opening sensor 17, which detects the opening (throttle position) of the throttle valve 16, are provided on the downstream side.

[0016] On the downstream side of the throttle valve 16, an expansion tank 18 is provided, and an intake manifold pressure sensor 19, which detects pressure in the intake manifold, is provided in the expansion tank 18. An intake port 20 for directing air into the combustion chamber 21 of each cylinder of the internal combustion engine 10 is connected to the expansion tank 18. An electromagnetic fuel injector 30 is mounted on the cylinder, which injects fuel directly into the combustion chamber 21 of the respective cylinder of the internal combustion engine 10. A spark plug 22 (an example of an ignition mechanism) is mounted on a cylinder head 11B of each cylinder, and the air-fuel mixture in the combustion chamber 21 is ignited by means of a spark discharge from the spark plug 22 of the cylinder.

[0017] An exhaust pipe 23 of the internal combustion engine 10 is equipped with an air-fuel ratio sensor 24, which detects the air-fuel ratio of the exhaust gas. A catalyst layer 25 and a particle removal layer 35 are provided on the downstream side of the air-fuel ratio sensor 24. The catalyst layer 25 is a layer that includes an exhaust gas purification catalyst, such as a three-way catalytic converter. The particle removal layer 35 is a layer that primarily removes particles from the exhaust gas. Examples of particle removal layers include a gasoline particulate filter (GPF) and a four-way GPF, in which a catalyst is mounted on the GPF. A PM sensor 36 is provided on the downstream side of the particle removal layer 35, which detects the concentration of particles (PM) in the exhaust gas. The A / F sensor 24 and the PM sensor 36 are examples of an exhaust gas sensor which detects a quantity of a predetermined component contained in the exhaust gas.A hydrocarbon (HC) sensor, a NOx sensor, an O2 sensor and / or the like can be used instead of or in addition to the A / F sensor 24 and the PM sensor 36.

[0018] A water temperature sensor 26, which detects the coolant temperature, and a knock sensor 27, which detects knocking, are mounted on a cylinder block 11A of the internal combustion engine 10. A crank angle sensor 29, which outputs a pulse signal whenever a crankshaft 28 rotates through a predetermined crank angle, is mounted on an outer circumferential side of the crankshaft 28. Based on the crank angle signal from the crank angle sensor 29, a crank angle and an engine speed are determined. A combustion pressure sensor (CPS) 38, which detects a pressure in the combustion chamber 21, is mounted on the combustion chamber 21 of the internal combustion engine 10. Furthermore, a combustion chamber temperature sensor may be provided, which detects a temperature inside the combustion chamber 21.

[0019] The output signals from these various sensors are input to an ECU 40. The ECU 40 is an electronic control unit, primarily comprising a microcomputer, which implements various controls for the internal combustion engine 10 using the signals from the different sensors. The ECU 40 calculates a fuel injection quantity based on the operating condition of the internal combustion engine 10 in order to control fuel injection from the fuel injector 30 and to control the ignition timing of the spark plug 22.

[0020] As in Fig. As shown in Figure 2, the fuel injection valve 30 is a solenoid-type fuel injection device and comprises a needle-shaped valve body 51 and a body 52 in which the valve body 51 is received. Control of an excitation of the solenoid coil enables the valve body 51 to move within the body 52 in the vertical direction. Fig. 2 to glide.

[0021] A tip end 53 of the body 52 has a substantially hemispherical shape. Several injection holes 60 for injecting fuel are formed in the tip end 53. An annular fuel passage 54, extending in the axial direction of the body 52, is formed between the inner surface of the body 52 and the outer surface of the valve body 51. A seat section 56, onto which a tip section 55 of the valve body 51 is placed, is formed on the inner surface of the tip end section 53 of the body 52. ​​A blind chamber 57 is formed on the tip end of the body 52 with respect to the seat section 56 to collect fuel that is distributed annularly in the fuel passage 54 and to direct the fuel to the injection hole 60. The tip end 53 of the body 52 can be referred to as a nozzle tip of the fuel injection valve 30.

[0022] When the solenoid coil is not energized, the tip section 55 of the valve body 51 is positioned against, or in contact with, the seat section 56 to block the fuel passage 54 from the injection port 60, thereby stopping fuel injection. Alternatively, when the solenoid coil is energized, the tip section 55 of the valve body 51 is lifted from the seat section 56 to connect the fuel passage 54 to the injection port 60. As a result, fuel is injected directly into the fuel passage 54 and conveyed via the blind chamber 57 from the injection port 60 to the combustion chamber of the internal combustion engine 10.

[0023] As in Fig. As shown in Figure 3, the ECU 40 comprises a load calculation unit 41, a soot production quantity calculation unit 42, a selection unit 43, an injection control unit 44, and an ignition control unit 48. The injection control unit 44 comprises a pattern control unit 45, an injector control unit 46, and a pump control unit 47.

[0024] The load calculation unit 41 calculates an operating load and a rotational speed of the internal combustion engine 10 based on measured values ​​from the intake air flow rate sensor 13, the intake air temperature sensor 14, and the crankshaft angle sensor 29. The measured values ​​of the various sensors obtained using the load calculation unit 41, the calculated operating load, and the calculated rotational speed are output to the soot production quantity calculation unit 42.

[0025] The soot production quantity calculation unit 42 obtains the measured values ​​from the A / F sensor 24, the PM sensor 36, and the water temperature sensor 26. The soot production quantity calculation unit 42 calculates a soot production quantity in the combustion chamber 21 and a deposit accumulation quantity in the combustion chamber 21 and the fuel injection valve 30. The measured values ​​from the various sensors obtained using the soot production quantity calculation unit 42 and the calculated soot production quantity are output to the selection unit 43 together with the data input by the load calculation unit 41.

[0026] The soot production quantity calculation unit 42 is preferably configured to calculate the soot production quantity and the deposit accumulation quantity based on the measured values ​​of various sensors and an operating state and operating profile of the internal combustion engine 10. In particular, the operating states can include one or more parameters selected from an operating load and speed of the internal combustion engine 10, a number and timing of fuel injections, an ignition timing, a fuel pressure and fuel temperature of the fuel injected by the fuel injector 30, an air-fuel ratio of the exhaust gas (A / F), a coolant temperature, an intake air temperature, an exhaust gas temperature, a temperature in the combustion chamber 21, and the like. The operating profile can utilize a change in these parameters over time.

[0027] The soot production quantity calculation unit 42 is configured to calculate the soot production quantity with reference to a map or similar stored in the ECU 40. The ECU 40 stores a map or a mathematical equation. This map or mathematical equation links the operating state of the internal combustion engine 10, sensor readings 50, and various parameters calculated from these readings with the temperature and pressure in the internal combustion engine 10 during the compression stroke and the soot production quantity.

[0028] For example, as in Fig. Figure 4 shows that the amount of soot produced is calculated based on a relationship between a time interval J1 from an end-of-injection (EOI) time to an ignition time, the fuel pressure at the time of injection, and the amount of soot produced. The vertical axis in Fig. Figure 4 shows the fuel pressure at the time of injection, the horizontal axis shows the time interval J1, and the curved dashed lines show the amount of soot produced. The amount of soot produced decreases along the direction of the arrow. Fig. 4. That is, the longer the time interval J1 and the higher the fuel pressure at the time of injection, the lower the soot production quantity. The soot production quantity calculation unit 42 is configured such that it obtains the time interval J1 and the fuel pressure and calculates the soot production quantity based on Fig. 4 calculated.

[0029] Furthermore, the soot production quantity calculation unit 42 can calculate the soot production quantity S, for example, based on a component quantity of a reduction target component in the exhaust gas, which is detected using the exhaust gas sensor, such as the A / F sensor 24 and the PM sensor 36. As in the Fig. 5 and Fig. As shown in Figure 6, the amounts of particulate matter (PM) and hydrocarbons (HC), which correspond to the reduction target component in the exhaust gas, also increase with increasing soot production. Therefore, the soot production amount can be calculated based on the measured values ​​of the A / F sensor 24 and the PM sensor 36.

[0030] Fig. Figure 7 shows changes in the exhaust gas sensor reading and the calculated soot production quantity due to switching or changing the injection mode. The horizontal axis in Fig. Figure 7 indicates time, and the vertical axis shows the PM quantity, the HC quantity, and the soot quantity (calculated value) from top to bottom in that order. From time t0 to time t1, fuel injection is performed in a normal mode injection pattern, and the PM quantity, HC quantity, and soot quantity increase over time. At time t1, the soot quantity exceeds a soot reduction threshold X1. Therefore, at time t1, a switch from normal mode to soot reduction mode is performed, and after time t1, fuel injection is performed in the soot reduction mode injection pattern. Consequently, the PM quantity, HC quantity, and soot quantity are significantly reduced immediately after the switchover time t1 and subsequently stabilized at low values.

[0031] As in Fig. As shown in Figure 8, the amount of deposit accumulation can be calculated based on a relationship between the time interval J1 from the end of injection (EOI) to the ignition time, the intensity of the airflow in the combustion chamber 21 at the time of injection, and the amount of the increase and decrease in deposit. The vertical axis in Fig. Figure 8 shows the intensity of the airflow, the horizontal axis shows the time interval J1, and each line of the curved solid and dashed lines shows the amount of an increase and decrease in deposition. The curved solid line in Fig. Figure 8 shows a zero-change line 2, where there is no increase or decrease in the deposit (amount of increase and decrease = 0). As the upward-pointing arrow indicates, if the airflow is more intense than the zero-change line 2 and the time interval J1 is long, the amount of deposit accumulation decreases. As the downward-pointing arrow indicates, if the airflow is weaker than the zero-change line 2 and the time interval J1 is short, the amount of deposit accumulation increases. The soot generation quantity calculation unit 42 is configured to obtain the time interval J1 and the intensity of the airflow in the combustion chamber 21 and to calculate the amount of deposit accumulation based on this. Fig. 8. Then the amount of deposit accumulation can be calculated by integrating the amount of the increase and decrease in deposit. The intensity of the airflow in the combustion chamber 21 can, for example, be calculated based on the rotational speed and load of the internal combustion engine 10.

[0032] The operating load and speed of the internal combustion engine 10, calculated using the load calculation unit 41, and the soot quantity calculated using the soot production quantity calculation unit 42, are stored in a storage unit of the ECU 40. In particular, the storage unit stores, as a map or equation, a relationship between the time of actual fuel injection (injection implementation time) and the quantity of the reduction target component contained in the exhaust gas at the same time, for each of the operating load and speed of the internal combustion engine 10.

[0033] The selection unit 43 switches the fuel injection mode of the fuel to be injected during the compression stroke of the internal combustion engine 10 between the soot reduction mode and another injection mode based on a predetermined switching condition and selects the fuel injection mode. The soot reduction mode corresponds to an injection mode that is set to prevent fuel from remaining on the tip end face with respect to the seat section 56 of the valve body 51 of the fuel injector 30, thereby reducing the generation of soot from the remaining fuel.Examples of injection modes that differ from the soot reduction mode include an injection mode (normal mode) that is normally executed when fuel is injected into the internal combustion engine 10, a deposit removal mode for removing a deposit that has accumulated on the fuel injector 30, and the like. The normal mode is set to prioritize fuel consumption by the internal combustion engine 10 and suppression of the reduction target component in the exhaust gas. The deposit removal mode is set to inject high-pressure fuel to remove a deposit that has accumulated on the tip 53 of the fuel injector 30.

[0034] The soot reduction mode is set to reduce the amount of soot produced compared to other injection modes. Specifically, the soot reduction mode is set to limit the amount of fuel remaining at the tip end of the tip section 55 of the valve body 51, relative to the position where the tip section 55 contacts the seat section 56 when the fuel injector 30 is closed, thereby reducing soot production.The tip end of the fuel injector 30, with respect to the position where the tip section 55 of the valve body 51 contacts the seat section 56, corresponds to the blind chamber 57 and the tip end 53, in which the injection orifice 60 is formed, and corresponds to a section exposed to the combustion chamber 21, even when the valve body 51 is in contact with the seat section 56 and the fuel injector 30 is in the closed state. The soot reduction mode makes it possible to limit the amount of fuel remaining in the blind chamber 57 and the tip end 53, in which the injection orifice 60 is formed, when the valve body 51 is placed on the seat section 56 after a fuel injection has taken place.Consequently, when the fuel injector 30 is in the closed state, the amount of fuel exposed to the atmosphere in the combustion chamber 21 can be reduced, and therefore the amount of soot produced can be reduced. The soot reduction mode effectively suppresses the adhesion of wet fuel, which tends to occur during fuel injection in the compression stroke of the internal combustion engine 10. Therefore, this configuration allows for the suppression of PM generation due to soot production and enables fuel injection during the compression stroke.

[0035] For example, the soot reduction mode can be set so that the number of fuel injections during the compression stroke of the internal combustion engine 10 is lower than the number of injections in other injection modes, such as normal mode. Reducing the number of injections allows for a reduction in the number of opening and closing cycles of the fuel injector 30. In this way, the configuration can limit the amount of fuel remaining in a wet state in the sack chamber 57 of the fuel injector 30 or adhering to the tip end 53 or the like after fuel injection, thereby reducing the amount of soot produced.

[0036] Fig. Figure 9 shows an injection pattern in fuel consumption priority mode and an injection pattern in soot reduction mode, which are examples of normal operation. In fuel consumption priority mode, the fuel injection during the compression stroke is split into two injections. In soot reduction mode, however, the fuel injection during the compression stroke is performed only once. Soot is formed from the fuel that remains in the waste chamber 57 of the fuel injector 30 and at the tip end 53 after each injection. Therefore, soot reduction mode halves the opportunities for soot formation compared to fuel consumption priority mode.

[0037] Furthermore, in soot reduction mode, for example, the opening and closing speed of the fuel injector 30 during fuel injection in the compression stroke of the internal combustion engine 10 can be set faster than the opening and closing speed of the fuel injector 30 in other injection modes. Increasing the opening and closing speed of the fuel injector 30 allows for an interruption of the fuel supply. Therefore, this configuration makes it possible to limit the amount of fuel remaining in the chamber 57 of the fuel injector 30 and adhering to the tip 53 or the like after fuel injection, thereby reducing the amount of soot produced.

[0038] Furthermore, the soot reduction mode can, for example, be set such that the temperature in the combustion chamber 21 is higher during fuel injection in the compression stroke of the internal combustion engine 10 than the temperature in the combustion chamber 21 in other injection modes. Increasing the temperature in the combustion chamber 21 promotes fuel atomization. Therefore, this configuration can limit the amount of fuel remaining in the sac 57 of the fuel injector 30 and adhering to the tip 53 or the like after injection, thus reducing the amount of soot produced. Furthermore, this configuration prevents fuel from adhering to the combustion chamber 21 in a wet state, thereby also reducing the amount of soot produced.

[0039] Furthermore, the soot reduction mode can, for example, be set such that the fuel temperature at the time of fuel injection during the compression stroke of the internal combustion engine 10 is higher than the fuel temperature in other injection modes. Increasing the fuel temperature promotes atomization of the fuel sprayed into the combustion chamber 21. Therefore, this configuration can suppress the formation of a portion of fuel remaining in the sac 57 of the fuel injector 30 and adhering to the tip 53 or the like after fuel injection, thereby reducing the amount of soot produced. Furthermore, this configuration allows for limiting fuel adhesion to the combustion chamber 21 in a wet state, thus also reducing the amount of soot produced.

[0040] The specific embodiment of the soot reduction mode described above can be used alone or in combination. The specific soot reduction mode can be selected appropriately according to the readings from the various sensors, the operating state and operating history of the internal combustion engine 10, and the like. The soot reduction mode can be set to limit the amount of fuel remaining at the tip end with respect to the seat section 56 of the valve body 51 of the fuel injector 30, thereby enabling a reduction in soot compared to other injection modes.This means that the soot reduction mode can be set to allow the retention of fuel at the tip end side with reference to the seat section 56 of the valve body 51 of the fuel injector 30 to be limited by means other than reducing the number of injections, increasing the opening and closing speed of the fuel injector 30 and increasing the temperature in the combustion chamber 21 or increasing the fuel temperature during injection, as described above.

[0041] The selection unit 43 can be configured to select the soot reduction mode if the soot production quantity S, calculated using the soot production quantity calculation unit 42 based on the operating state and operating history of the internal combustion engine 10, exceeds a predetermined soot reduction threshold X1 (S > X1). For example, the selection unit 43 can select the soot reduction mode when S > X1 and can select the normal mode when S ≤ X1. This configuration calculates the soot production quantity from the operating state and operating history of the internal combustion engine 10, thus enabling the selection of the soot reduction mode before the soot production quantity actually increases and suppressing any increase in the soot production quantity.

[0042] Furthermore, the selection unit 43 can, for example, select the injection mode based on the quantity of the reduction target component in the exhaust gas, which is detected using the exhaust gas sensor, such as the A / F sensor 24 and the PM sensor 36. As described in the Fig. 5 and Fig. As shown in Figure 6, with increasing soot production, the amounts of particulate matter (PM) and hydrocarbons (HC), which correspond to the reduction target component in the exhaust gas, also increase. Therefore, the selection unit 43 can set an exhaust gas component threshold Y1 for a predetermined parameter P, which specifies the amount of the reduction target component in the exhaust gas. The selection unit 43 can select the soot reduction mode when P > Y1, and it can select the normal mode when P ≤ Y1. This configuration allows the system to detect the changing state of the internal combustion engine 10 over time from the exhaust gas sensor reading and enables the appropriate soot reduction mode to be selected at any given time, thereby suppressing an increase in the amount of soot produced.

[0043] The soot reduction threshold X1 and the exhaust component threshold Y1 can be pre-stored in the ECU 40. Alternatively, the soot reduction threshold X1 and the exhaust component threshold Y1 can be set or updated based on the detection value obtained in a combustion cycle prior to the combustion cycle to be executed, or similar data.

[0044] The selection unit 43 can be configured to set a prohibition flag to prevent the selection of the soot reduction mode based on the operating state and history of the internal combustion engine 10. For example, the selection unit 43 can prohibit the selection of the soot reduction mode if an anomaly has occurred in a system on the vehicle, including the fuel injection system 1, or if combustion in the internal combustion engine 10 is unstable. Specifically, the selection unit 43 can set the flag to prevent the selection of the soot reduction mode if an anomaly is detected in the fuel system and fail-safe control is executed. Furthermore, the selection unit 43 can be configured to clear or cancel the prohibition flag if the condition described above for setting the prohibition flag is no longer met.Alternatively, a condition to remove the prohibition flag can be set separately from the condition to set the prohibition flag.

[0045] Furthermore, the selection unit 43 can be configured to select the soot reduction mode in cases where there is a concern that the amount of soot produced will increase. For example, the selection unit 43 can periodically select the soot reduction mode if the operating time of the internal combustion engine 10 exceeds a predetermined operating time or the like. The selection unit 43 can also compare the soot production quantity in this mode with the soot production quantity in normal mode and select the soot reduction mode accordingly. Furthermore, the processing described above can be performed, and training can be carried out to select the appropriate soot reduction mode.

[0046] The injection control unit 44 sets the injection pattern of the fuel to be injected during the compression stroke of the internal combustion engine 10 according to the injection mode selected by the selection unit 43. The injection control unit 44 controls the fuel injector 30 and the high-pressure pump 33 to perform fuel injection in the set injection pattern. The injection control unit 44 comprises the pattern control unit 45, the injector control unit 46, and the pump control unit 47. The pattern control unit 45 sets the injection pattern of the fuel to be injected during the compression stroke of the internal combustion engine 10 according to the injection mode selected by the selection unit 43. The injector control unit 46 controls the fuel injector 30. The pump control unit 47 controls the high-pressure pump 33.

[0047] The pattern control unit 45 sets the fuel injection timing and adjusts the injection pattern according to the set injection timing. The pattern control unit 45 adjusts the injection pattern according to the injection mode selected by the selection unit 43 when the set fuel injection timing corresponds to the compression stroke of the internal combustion engine 10. The pattern control unit 45 also executes a control command at the injector control unit 46 and the pump control unit 47 according to the injection pattern.

[0048] The model control unit 45 determines the injection timing of fuel injected by the fuel injector 30 at a predetermined calculation time, which is set for each combustion cycle of the internal combustion engine 10. In particular, the model control unit 45 determines whether the injection timing is to be set during the compression stroke of the internal combustion engine 10, based on the operating state of the internal combustion engine 10 calculated by the load calculation unit 41, the operating profile, and the sensor readings 50.

[0049] The pattern control unit 45 determines whether the interior of the combustion chamber 21 of the internal combustion engine 10 meets a predetermined high-temperature condition, based on the load and rotational speed of the internal combustion engine 10, the sensor readings 50, and the like, when the soot reduction mode is selected by the selection unit 43. If it is determined that the interior of the combustion chamber 21 meets the predetermined high-temperature condition, the pattern control unit 45 can adjust the injection timing during the compression stroke of the internal combustion engine 10. It should be noted that the predetermined high-temperature condition corresponds to a condition in which the interior of the combustion chamber 21 is in a high-temperature state during the compression stroke, such that the amount of the reduction target component becomes less than a predetermined value.The predetermined high-temperature condition can be set based on the operating profile of the internal combustion engine 10 or an operating profile obtained with another internal combustion engine 10 that has an equivalent structure to that of the internal combustion engine 10.

[0050] The pattern control unit 45 refers to a map or similar stored in the ECU 40 and determines whether the predetermined high-temperature condition is met. The ECU 40 stores a map or a mathematical equation. This map or equation links the operating state of the internal combustion engine 10, the sensor readings 50, and various parameters calculated from these readings with the temperature and pressure in the internal combustion engine 10 during the compression stroke and the quantity of the reduction target component. A predetermined numerical range that meets the high-temperature condition can be set based on the map or equation stored in the ECU 40 for each of the operating conditions of the internal combustion engine 10, the sensor readings 50, and the various parameters calculated from these readings.

[0051] In a configuration where the injection timing is set during the compression stroke, the pattern control unit 45 can set an optimal injection timing that makes it possible to further reduce the amount of the reduction target component in the exhaust gas and reduce fuel consumption.

[0052] The injection timing and injection pattern can be reset based on the measured values ​​obtained from various sensors at the time of fuel injection. For example, the soot production quantity can be recalculated, the injection mode can be reselected, and the injection pattern can be reset based on each measured value obtained at a predetermined time interval after the injection timing in the compression stroke has been set to a predetermined calculation time, which is set for each combustion cycle of the internal combustion engine 10.

[0053] The injector control unit 46 calculates the fuel injection quantity based on the engine speed, load, target air-fuel ratio, the air-fuel ratio measured by the exhaust gas sensor, air-fuel ratio feedback (FB), and similar parameters of the internal combustion engine 10. Furthermore, the injector control unit 46 calculates the fuel injection duration based on the injection quantity and fuel pressure. The injector control unit 46 controls the opening and closing of the needle valve of the fuel injector 30 based on the injection start time and injection duration set by the model control unit 45, and injects fuel into the combustion chamber 21.The calculated injection quantity, the calculated injection duration and the like can be mapped or can be mathematically linked to the reduction target component in the exhaust gas and can be stored in the storage unit of the ECU 40.

[0054] The pump control unit 47 controls the output of the high-pressure pump 33 and the output of the low-pressure pump 34 based on the reading of the fuel pressure sensor 37. The pump control unit 47 can be configured to set a target fuel pressure and allow fuel injection during the combustion or power stroke if the reading of the fuel pressure sensor 37 approaches the target fuel pressure. When the fuel pressure is high at the time of fuel injection, the shear force acting on the injected fuel generally increases. This results in smaller injected fuel droplets and an increase in the number of collisions between air molecules and the fuel droplets per unit time. Consequently, the fuel is distributed satisfactorily, thus enabling satisfactory fuel-air mixture formation.However, when the fuel pressure is high, the fuel impulse is also large. Therefore, there is a concern that a suitable fuel-air mixture may not form due to fuel passing through spark plug 22 when an injection is performed immediately before ignition to attempt to position a rich air-fuel mixture around spark plug 22. Furthermore, there is a concern that the flow of an air-fuel mixture in the combustion chamber 21 may be impaired by the increased impulse. Because of these concerns, the formation of an air-fuel mixture around the spark plug between fuel injection and ignition may become difficult.

[0055] The ignition control unit 48 adjusts the timing and duration of the excitation of the spark plug 22 based on the injection pattern set by the pattern control unit 45 and executes ignition control of the spark plug 22. The ignition control unit 48 adjusts the ignition timing according to the selected injection mode and the correspondingly set injection pattern to ensure knock resistance during fuel combustion and to create a rich air-fuel mixture around the spark plug 22.

[0056] In a configuration where, for example, the ignition control unit 48 forms a rich air-fuel mixture around the spark plug 22 for combustion, the fuel injection timing is adjusted so that an air-fuel mixture with a predetermined air-fuel ratio is formed near the tip end of the spark plug 22 at the fuel ignition timing set for each operating condition.

[0057] Furthermore, the ignition control unit 48 can, for example, have the function of a knock control system (KCS), which controls knocking according to the ignition timing. The KCS detects knocking based on the signal from the knock sensor 27. The KCS gradually retards the ignition timing when knocking is detected and advances the ignition timing when knocking is no longer detected. By repeating this process, the KCS learns the knock ignition timing, which corresponds to a limit ignition timing at which knocking occurs.

[0058] In soot reduction mode, conditions such as the injection pattern, fuel pressure, or temperature of the injected fuel, as well as the pressure and temperature in the combustion chamber 21, can be modified compared to those in normal mode. Therefore, the knock resistance in soot reduction mode differs from the knock resistance in normal mode. To prevent a reduction in knock resistance due to the selection of the soot reduction mode, the ignition control unit 48 retards the ignition timing in soot reduction mode compared to the ignition timing in normal mode.

[0059] Furthermore, if the fuel pressure of injected fuel is excessively high during fuel injection in the compression stroke, the momentum of the fuel jet injected into the combustion chamber 21 can increase excessively. As a result, the fuel jet may pass the tip of the spark plug 22, and a rich air-fuel mixture may hardly form around the spark plug 22 at the time of ignition. Therefore, the ignition control unit 48 retards the ignition timing. In this way, the injection control unit 44 and the ignition control unit 48 adjust the time from fuel injection to ignition to a longer duration. This configuration retards the ignition timing to enable ignition to occur in a state where a rich air-fuel mixture has formed around the spark plug 22.In this way, the configuration enables the formation of a rich air-fuel mixture around spark plug 22 and the implementation of stable combustion.

[0060] The ECU 40 can be configured to correct, switch, or learn the injection mode, injection timing and pattern, fuel pressure and temperature control, combustion chamber 21 pressure and temperature control, ignition control, and the like, as described above, based on the measured values ​​obtained from the various sensors at the time of fuel injection. Furthermore, the ECU 40 can be configured to allow switching of the injection pattern or the like based on a set or cleared prohibition flag.

[0061] For example, the ECU 40 can pre-store injection patterns for each injection mode for the internal combustion engine 10 corresponding to a control target. Additionally, the ECU 40 can correct the injection pattern, if necessary, to more closely match another stored injection pattern, based on the sensor readings and an estimated value, such as the amount of soot produced, which is calculated from these readings when fuel injection is performed in the selected injection mode.

[0062] In particular, the ECU 40 can correct the injection pattern so that it is closer to the injection pattern in soot reduction mode when fuel injection is performed in the normal mode injection pattern, in response to an estimate based on the exhaust gas sensor reading that the amount of soot produced will increase. Specifically, the ECU 40 can increase the opening and closing speed of the fuel injector 30, reduce the number of injections, and increase the fuel temperature and the temperature in the combustion chamber 21 to correct the injection pattern so that it is close to the injection pattern in soot reduction mode. The correction amount can be set to increase with the increasing amount of soot produced.For example, in a case where the fuel temperature at the time of injection in normal mode is equal to T1 and where the fuel temperature at the time of injection in soot reduction mode is equal to T2, the ECU 40 can set a coefficient A (0 ≤ A ≤ 1) that increases with increasing amount of soot produced and use a correction amount (A × (T2 - T1)) for the fuel temperature.

[0063] Furthermore, the ECU 40 can, for example, switch the injection pattern to a different stored injection pattern as needed, based on the readings from the various sensors and an estimated value, such as the amount of soot produced, which is estimated from these readings when fuel injection is performed in the selected injection mode. Specifically, the ECU 40 can switch the injection pattern to the soot reduction mode when fuel injection is performed in the normal mode injection pattern, in response to an estimate that the amount of soot produced will increase, based on the exhaust gas sensor reading.

[0064] In a case where the ECU 40 corrects or switches the injection pattern, and when the ECU 40 changes the control parameters, such as the fuel temperature and the temperature in the combustion chamber 21, the ECU 40 preferably changes the command value gradually rather than changing the command value suddenly. Furthermore, the ECU 40 preferably adjusts the ignition timing to suppress knocking and produce combustion that forms a rich air-fuel mixture around the spark plug 22, according to the correction or switching of the injection pattern.

[0065] For example, the ECU 40 can store a relationship, in a format such as a conformity map, between the sensor readings 50, various estimated values ​​calculated from these readings for each operating state and operating profile of the internal combustion engine 10, and the respective injection patterns selected and corrected at that time. The ECU 40 can select the injection pattern according to the operating state and operating profile of the internal combustion engine 10 based on this conformity map or similar. Furthermore, this conformity map or similar can be corrected for the respective operation of the internal combustion engine 10.

[0066] The injection control process executed by the ECU 40 is described with reference to the in Fig. The flowchart shown in section 10 describes this process. This flowchart is executed repeatedly at predetermined intervals.

[0067] First, in step S101, it is determined whether a set time, such as an injection point, has been reached. This set time corresponds to a predetermined calculation point that is set for each combustion cycle of the internal combustion engine 10. If the set time has been reached, the process continues with step S102. If the set time has not been reached, the process continues with step S113.

[0068] When the set time is reached, the process proceeds to step S102, in which the ECU 40 obtains the operating status of the internal combustion engine 10 and sensor readings from the various sensors. Specifically, readings such as the load of the internal combustion engine 10, the amount of unburned fuel, and the number of particles in the exhaust gas (detected using the A / F sensor 24 and the particle sensor 36), the engine coolant temperature of the internal combustion engine 10 (from the coolant temperature sensor 26), the intake air flow rate (from the intake air flow rate sensor 13), the intake air temperature (from the intake air temperature sensor 14), the pressure in the combustion chamber 21 (from the combustion pressure sensor 38), and the crankshaft angle signal (from the crankshaft angle sensor 29) are obtained as needed. The process then proceeds to step S103.

[0069] In step S103, the soot production quantity S and the deposit quantity D are calculated. Specifically, the soot production quantity S is calculated based on the PM component quantity and the HC component quantity in the exhaust gas, which are detected using the exhaust gas sensor, and with reference to the values ​​in the Fig. 5 and Fig. The relationship shown in Figure 6 (stored in ECU 40) is estimated. Furthermore, the deposit D is estimated based on the relationship between the time interval J1 from EOI to the ignition time, the intensity of the airflow in the combustion chamber 21 at the time of injection, and the amount of any increase and decrease in the deposit, with reference to the relationship shown in Figure 6. Fig. The relationship shown in step 8 (stored in ECU 40) is estimated. The process then continues with step S104.

[0070] In step S104, it is determined whether the soot production quantity S exceeds the soot reduction threshold X1. If S > X1, the process continues with step S105. If S ≤ X1, the process continues with step S110, in which the normal mode is selected. It should be noted that instead of step S104, the selection of the injection mode can be determined based on the exhaust gas sensor reading obtained in step S102. Specifically, the exhaust gas component threshold Y1 can be set for the predetermined parameter P, which specifies the quantity of the reduction target component in the exhaust gas. If P > Y1, the process continues with step S105. If P ≤ Y1, the process continues with step S110.

[0071] Step S105 determines whether the prohibition flag is set or not. For example, if the internal combustion engine 10 is in the start-up phase and the operating state is unstable, the prohibition flag is set. If the prohibition flag is not set, the process continues with step S107. If the prohibition flag is set, the process continues with step S106.

[0072] Step S106 determines whether the prohibition flag can be cleared. For example, if the internal combustion engine 10 completes the start-up process and the operating state stabilizes, so that the condition for setting the prohibition flag is no longer met, the prohibition flag can be cleared. If the prohibition flag can be cleared, the process continues to step S107. If the prohibition flag cannot be cleared, the process proceeds to step S110, in which normal mode is selected.

[0073] Step S107 determines whether the estimated deposit accumulation amount D exceeds the deposit threshold X2. If D > X2, the process proceeds to step S108, where the deposit removal mode is selected. If D ≤ X2, the process proceeds to step S109, where the soot reduction mode is selected.

[0074] Following the selection of the injection mode in steps S108 to S110, the process continues with step S111. In step S111, the fuel injection timing and injection pattern are set. If the injection timing is set during the compression stroke of the internal combustion engine 10, the injection pattern is set according to the injection mode selected in steps S108 to S110. Following step S111, the process proceeds to step S112.

[0075] In step S112, the fuel ignition timing is adjusted according to the injection pattern set in step S109. For example, if the soot reduction mode is selected, the ignition timing is retarded compared to normal mode to ensure knock resistance and create a rich air-fuel mixture around spark plug 22 to stabilize combustion. Following step S112, the process proceeds to step S113.

[0076] When it is determined in step S113 that the set injection time has been reached, the process continues with step S114, in which fuel injection is performed according to the set injection pattern. For example, if the soot reduction mode is selected in step S110, fuel is injected in the injection pattern that prevents fuel from remaining at the tip end face with respect to the seat section 56 of the valve body 51 at the fuel injector 30 when fuel injection occurs during the compression stroke. In particular, the number of injections during the compression stroke is reduced compared to other injection modes. Alternatively, the opening and closing speed of the fuel injector 30 is increased. Alternatively, the temperature in the combustion chamber 21 and the fuel temperature at the time of fuel injection are increased.Following step S114, the process proceeds to step S115. If the injection timing is not available, the process continues with step S115.

[0077] If step S115 determines that the set ignition timing has been reached, the process continues with step S116, in which fuel ignition is performed, and then the process ends. If the ignition timing has not been reached, the process ends without executing step S116.

[0078] As described above, according to the in Fig.The flowchart shown in Figure 10 selects the injection mode at the set time. Furthermore, the injection timing, injection pattern, and ignition timing are set according to the selected injection mode. Once the set injection time is reached, fuel injection is performed according to the set injection pattern. Fuel is then ignited at the ignition timing set to ensure the knock resistance and other parameters are met according to the set injection pattern.

[0079] The ECU 40 can be configured to execute the processes of steps S102 to S112 at a different time than the set time. For example, the processes of steps S102 to S110 are executed at predetermined intervals to select the injection mode, and the injection mode can be switched if the selected injection mode at that time differs from the selected injection mode at the set time. Subsequently, the processes of steps S111 and S112 can be executed for the switched injection mode. Furthermore, after the injection mode is selected in steps S108 to S110, a step can be added to correct the selected injection mode based on the measured values ​​from various sensors, which are obtained before the injection is executed in step S113.

[0080] The embodiment described above produces the following effects.

[0081] According to the ECU 40, the selection unit 43 switches the injection mode of the fuel to be injected during the compression stroke of the internal combustion engine 10 between the soot reduction mode, which serves to reduce the soot produced at the fuel injector 30, and another injection mode that differs from the soot reduction mode, based on a predetermined switching condition. The selection unit 43 sets the injection mode. Subsequently, the injector control unit 46 controls the fuel injector 30 to perform fuel injection at the injection time set in the compression stroke, based on the injection mode selected by the selection unit 43. Therefore, the configuration allows fuel injection in soot reduction mode to be performed as needed, based on the predetermined switching condition, thereby suppressing soot production.

[0082] Furthermore, the soot reduction mode corresponds to an injection mode configured to limit fuel residue on the tip end face with respect to the seat section 56 of the valve body 51 of the fuel injector 30, thereby reducing soot. Therefore, this configuration effectively suppresses wet fuel adhesion, which tends to occur during fuel injection in the compression stroke of the internal combustion engine 10. Consequently, this configuration suppresses PM generation due to soot production and enables fuel injection to be performed during the compression stroke.

[0083] The selection unit 43 can be configured to select the soot reduction mode under a condition that the soot production quantity S, as calculated based on the operating state and operating history of the internal combustion engine 10, exceeds a predetermined soot reduction threshold. This configuration calculates the soot production quantity from the operating state and operating history of the internal combustion engine 10 in order to enable the soot reduction mode to be selected before the soot production quantity actually increases and to suppress any increase in the soot production quantity.

[0084] The selection unit 43 can be configured to select the soot reduction mode if the amount of the reduction target component in the exhaust gas, detected by the exhaust gas sensor, exceeds the predetermined exhaust gas component threshold Y1. This configuration allows the soot reduction mode to be selected appropriately according to the current state of the internal combustion engine 10, thereby suppressing an increase in the amount of soot produced.

[0085] The soot reduction mode can be set to reduce the number of fuel injections during the compression stroke of the internal combustion engine 10, compared to other injection modes, thereby reducing the amount of soot produced. Reducing the number of fuel injections also reduces the number of times the fuel injector 30 opens and closes. In this way, the configuration reduces the likelihood of some fuel remaining in a wet state in the chamber 57 of the fuel injector 30, or adhering to the tip 53 or similar, after the fuel injector 30 closes to terminate fuel injection, thus reducing the amount of soot produced.

[0086] Furthermore, for example, in soot reduction mode, the opening and closing speed of the fuel injector 30 during fuel injection in the compression stroke of the internal combustion engine 10 can be set faster compared to other injection modes, thereby reducing the amount of soot produced. Increasing the opening and closing speed of the fuel injector 30 also allows for an interruption of the fuel supply. Therefore, this configuration can limit the amount of fuel remaining in the chamber 57 of the fuel injector 30 and adhering to the tip 53 after injection, thus reducing the amount of soot produced.

[0087] The temperature in the combustion chamber of the internal combustion engine can be increased in soot reduction mode, so that it is higher than in other injection modes when fuel injection occurs during the compression stroke of the internal combustion engine 10, thereby reducing the amount of soot produced. Increasing the temperature in the combustion chamber 21 promotes fuel atomization. Therefore, this configuration limits the amount of fuel remaining in the sac chamber 57 of the fuel injector 30 and adhering to the tip 53 after injection, thus reducing the amount of soot produced.

[0088] In soot reduction mode, the temperature of the fuel injected by the fuel injector 30 can be increased to a higher temperature than in other injection modes when fuel injection occurs during the compression stroke of the internal combustion engine 10, thereby reducing the amount of soot produced. Increasing the temperature of the injected fuel promotes fuel atomization in the combustion chamber 21. This configuration therefore limits the amount of fuel remaining in the waste chamber 57 of the fuel injector 30 and adhering to the tip 53 after injection, thus reducing the amount of soot produced.

[0089] The ignition control unit 48 can be configured to change the ignition timing for the ignition of fuel in the combustion chamber 21 according to the soot reduction mode, provided that the selection unit 43 has selected the soot reduction mode. The ignition control unit 48 makes it possible to adjust the ignition timing according to the selected injection mode and the correspondingly set injection pattern in order to ensure knock resistance during fuel combustion and to form a rich air-fuel mixture around the spark plug 22 to implement combustion.

[0090] The selection unit 43 can be configured to prohibit the selection of the soot reduction mode based on the operating state and history of the internal combustion engine 10. The selection unit 43 can prohibit the selection of the soot reduction mode if an anomaly has occurred in a system on the vehicle, including the fuel injection system 1, or if the combustion state in the internal combustion engine 10 is unstable. This configuration ensures the safe operation of the internal combustion engine 10, prioritizing the prevention of problems such as misfires in cases of unstable combustion.

[0091] The fuel injection control device of the present disclosure can be applied to both a diesel engine and a gasoline engine. That is to say, the fuel injection control device can be applied to a fuel injection control device that controls a fuel injection valve of a direct injection diesel engine.

[0092] Although the present disclosure was made according to the embodiments, it follows that the present disclosure is not limited to such embodiments and structures. The present disclosure includes various modifications and variations within the equivalence range. Furthermore, in addition to the various preferred combinations and configurations, other combinations and configurations with more, fewer, or only a single element also fall within the basic concept and scope of protection of the present disclosure.

Claims

[1] Fuel injection control device (40) configured to control a fuel injection system (1), the fuel injection system comprising a direct injection fuel injector (30) configured to inject high-pressure fuel directly into a combustion chamber (21) of an internal combustion engine (10) in a collector (32), the fuel injection control device comprising: a selection unit (43) which is configured such that this an injection mode of fuel to be injected in a compression stroke of the internal combustion engine, between a soot reduction mode in which fuel is prevented from remaining at a tip end face of a valve body (51) with respect to a seat section (56) at the fuel injector in order to reduce soot, and another injection mode which differs from the soot reduction mode, based on a predetermined switching condition, and selects the injection mode; and an injection control unit (44) which is configured to perform fuel injection which is set in the compression stroke of the internal combustion engine, based on the injection mode selected by the selection unit, wherein The soot reduction mode is set to increase the opening and closing speed of the fuel injector so that it is faster than that in any other injection mode when fuel injection is carried out during the compression stroke of the internal combustion engine in order to reduce the amount of soot produced. [2] Fuel injection control device according to claim 1, wherein the soot reduction mode is set to increase a temperature in a combustion chamber of the internal combustion engine such that it is higher than that in another injection mode when fuel injection is carried out in the compression stroke of the internal combustion engine in order to reduce an amount of soot produced. [3] Fuel injection control device (40) configured to control a fuel injection system (1), the fuel injection system comprising a direct injection fuel injector (30) configured to inject high-pressure fuel directly into a combustion chamber (21) of an internal combustion engine (10) in a collector (32), the fuel injection control device comprising: a selection unit (43) which is configured such that this an injection mode of fuel to be injected in a compression stroke of the internal combustion engine, between a soot reduction mode in which fuel is prevented from remaining at a tip end face of a valve body (51) with respect to a seat section (56) at the fuel injector in order to reduce soot, and another injection mode which differs from the soot reduction mode, based on a predetermined switching condition, and selects the injection mode; and an injection control unit (44) which is configured to perform fuel injection which is set in the compression stroke of the internal combustion engine, based on the injection mode selected by the selection unit, wherein The soot reduction mode is set to increase the temperature in a combustion chamber of the internal combustion engine so that it is higher than that in any other injection mode when fuel injection is carried out during the compression stroke of the internal combustion engine in order to reduce the amount of soot produced. [4] Fuel injection control device according to any one of claims 1 to 3, wherein the soot reduction mode is set to increase the temperature of the fuel to be injected by the fuel injector such that it is higher than that in any other injection mode when fuel injection is carried out in the compression stroke of the internal combustion engine in order to reduce the amount of soot produced. [5] Fuel injection control device (40) configured to control a fuel injection system (1), the fuel injection system comprising a direct injection fuel injector (30) configured to inject high-pressure fuel directly into a combustion chamber (21) of an internal combustion engine (10) in a collector (32), the fuel injection control device comprising: a selection unit (43) which is configured such that this an injection mode of fuel to be injected in a compression stroke of the internal combustion engine, between a soot reduction mode in which fuel is prevented from remaining at a tip end face of a valve body (51) with respect to a seat section (56) at the fuel injector in order to reduce soot, and another injection mode which differs from the soot reduction mode, based on a predetermined switching condition, and selects the injection mode; and an injection control unit (44) which is configured to perform fuel injection which is set in the compression stroke of the internal combustion engine, based on the injection mode selected by the selection unit, wherein The soot reduction mode is set to increase the temperature of the fuel to be injected by the fuel injector so that it is higher than that in any other injection mode when fuel injection is carried out during the compression stroke of the internal combustion engine, in order to reduce the amount of soot produced. [6] Fuel injection control device according to any one of claims 1 to 5, wherein the fuel injection system further comprises an exhaust gas sensor which is configured to detect a component in the exhaust gas from the internal combustion engine, wherein The selection unit is configured to select the soot reduction mode under a condition that the quantity of a reduction target component in the exhaust gas, detected using the exhaust gas sensor, exceeds a predetermined exhaust gas component threshold. [7] Fuel injection control device according to any one of claims 1 to 6, wherein the soot reduction mode is set to reduce the number of fuel injections that are injected in the compression stroke of the internal combustion engine compared to that in another injection mode in order to reduce the amount of soot produced. [8] Fuel injection control device (40) configured to control a fuel injection system (1), the fuel injection system comprising a direct injection fuel injector (30) configured to inject high-pressure fuel directly into a combustion chamber (21) of an internal combustion engine (10) in a collector (32), the fuel injection control device comprising: a selection unit (43) which is configured such that this an injection mode of fuel to be injected in a compression stroke of the internal combustion engine, between a soot reduction mode in which fuel is prevented from remaining at a tip end face of a valve body (51) with respect to a seat section (56) at the fuel injector in order to reduce soot, and another injection mode which differs from the soot reduction mode, based on a predetermined switching condition, and selects the injection mode; and an injection control unit (44) which is configured to perform fuel injection which is set in the compression stroke of the internal combustion engine, based on the injection mode selected by the selection unit, wherein The soot reduction mode is set to reduce the number of fuel injections during the compression stroke of the internal combustion engine compared to that in another injection mode, in order to reduce the amount of soot produced. [9] Fuel injection control device according to any one of claims 1 to 8, further comprising: an ignition control unit configured to change the ignition timing at which fuel is ignited in the combustion chamber according to the soot reduction mode, provided that the selection unit selects the soot reduction mode. [10] Fuel injection control device according to one of claims 1 to 9, wherein the selection unit is configured such that it selects the soot reduction mode under a condition that a soot production quantity corresponding to a soot production quantity calculated on the basis of an operating state and an operating history of the internal combustion engine exceeds a predetermined soot reduction threshold. [11] Fuel injection control device according to any one of claims 1 to 9, wherein the selection unit is configured such that it prohibits the selection of the soot reduction mode according to an operating state or operating sequence of the internal combustion engine.

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