Fuel injection control device

Abstract

A fuel injection control device (40) configured to control a fuel injection system (1), the fuel injection system including an accumulator (32) configured to store a high-pressure fuel, a direct injection fuel injection valve (30) configured to inject a high-pressure fuel in the pressure accumulator directly into a combustion chamber (21) of an internal combustion engine (10), and an exhaust gas sensor (24, 36) configured to detect a component in the exhaust gas from the internal combustion engine, the fuel injection control device comprising: a timing setting unit (43) configured to set a fuel injection timing in a second half of a compression stroke of the internal combustion engine when a component amount of a reduction target component in the exhaust gas detected by the exhaust gas sensor is greater than or equal to a predetermined value, under the condition that the internal combustion engine satisfies a predetermined high temperature condition at a predetermined calculation timing set for each combustion cycle of the internal combustion engine, and an injection control unit (45) configured to calculate an injection period of fuel based on the injection timing set by the timing setting unit, and to control the fuel injection valve based on the injection timing and injection period.

Description

Technical field

[0001] The present disclosure relates to a fuel injection control device configured to inject fuel into an internal combustion engine. State of the art

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

[0003] For example, JP 2012 - 159 005 A discloses a configuration to set a fuel injection period defined by an injection start timing (SOI) of fuel and an injection end timing (EOI) of fuel to coincide with an injection period that makes it possible to reduce PM and the like in an intake stroke of the internal combustion engine.

[0004] In addition, it is known from DE 10 2016 001 367 A1 to determine emission values ​​of the exhaust gases emitted by an internal combustion engine using driving condition signals, to compare them with emission limits and, if these are exceeded, to reduce them.

[0005] From DE 10 2011 006 363 A1 it is known to reduce an undesirable exhaust gas component, wherein a comparison value of an air ratio or an oxygen content is determined and compared with a current air ratio or oxygen content, and depending on a result of the comparison a correction value is determined to correct a value acting on the current air ratio or the current oxygen content in the intake manifold.

[0006] From DE 10 2007 061 468 A1, a real-time estimation of diesel engine emissions is known to enable an optimal estimation of emissions in a steady state and in a transient state, using a NOx model for the steady state, a particulate model for the steady state, a NOx model for the transient state and a particulate model for the transient state, each selected on the basis of the rate of change of the engine speed in order to reduce NOx and particulate emissions.

[0007] From DE 10 2016 123 830 A1 it is known to use an operating parameter with an emission value and / or a value from an exhaust system to control an actuator of an engine.

[0008] From DE 10 2005 044 544 A1 it is known to determine, depending on at least the load of an internal combustion engine, a first crank angle at which a first injection of fuel takes place, by means of which a lean mixture is produced, then to determine a second crank angle at which a second injection of fuel takes place, by means of which a richer mixture cloud embedded in the lean mixture is produced, and then a third injection of fuel takes place in the form of a stratified injection in order to produce a rich and ignitable fuel / air mixture.

[0009] From DE 103 47 474 A1 a method for outputting injection pulse widths in an internal combustion engine with direct fuel injection is known, wherein the internal combustion engine can be operated in different operating modes with different patterns of injection types and wherein each pattern is assigned to a working cycle of the internal combustion engine.

[0010] DE 103 16 112 A1 discloses a method for operating a compression-ignition internal combustion engine, in which an average gas temperature in the cylinder is determined during combustion in the combustion chamber, thereby calculating an average gas temperature gradient. A raw nitrogen oxide emission of the internal combustion engine is then determined either from a value of the average gas temperature gradient and / or from a maximum value of the average gas temperature in the cylinder, in order to adjust the engine parameters in such a way that a profile of the average gas temperature during combustion results in fewer NOx emissions.

[0011] From DE 102 49 755 A1 a method for exhaust gas aftertreatment with post-injection is known, in which a further reduction of the soot emission takes place independently of the type of internal combustion engine, in that the post-injection is controlled as a function of the detected particulate raw emission of the internal combustion engine immediately after a main injection during the combustion process. Summary of the invention

[0012] JP 2012 - 159 005 A describes that fuel injection during the intake stroke of the internal combustion engine is beneficial to reduce PM in the exhaust gas of the internal combustion engine.

[0013] In contrast, the person disclosing the present disclosure found the following as a result of serious research. Specifically, in a case where fuel injection is performed in a second half of a compression stroke of an internal combustion engine, injected fuel is rapidly vaporized in a combustion chamber of an internal combustion engine at a high temperature to thereby improve a combustion state and consequently reduce components (harmful components such as PM and unburned fuel) in the exhaust gas in some cases. Furthermore, the person disclosing the present disclosure found that, in some cases, setting a main injection timing of fuel in the second half of the compression stroke achieves a reduction target component in the exhaust gas.Exhaust gas is reduced rather than fixing the main injection timing in the intake stroke, depending on an operating condition of the internal combustion engine.

[0014] It is possible to estimate whether the fuel injection timing should be set either in the intake stroke or in the second half of the compression stroke based on the operating condition of the internal combustion engine and the like to enable reduction of the reduction target component in the exhaust gas. This means that a more suitable injection pattern can be adjusted in advance for each operating condition of the internal combustion engine. Setting the injection pattern based on the operating condition makes it possible, to a certain extent, to maintain the reduction target component amount in the exhaust gas within an appropriate numerical range.

[0015] In contrast, in a case where fuel is injected in the second half of the compression stroke, the time from fuel injection into the combustion chamber of the internal combustion engine until the fuel is ignited is shortened. Consequently, the target reduction component amount in the exhaust gas may increase depending on the combustion chamber condition.

[0016] In view of the above, it is an object of the present disclosure to provide a fuel injection control device configured to appropriately set an injection timing of fuel according to the state of the internal combustion engine and to reduce a reduction target component in the exhaust gas of the internal combustion engine.

[0017] It is an object of the present disclosure to provide a fuel injection control device for controlling a fuel injection system including: an accumulator for storing high-pressure fuel, a direct injection fuel injection valve for injecting high-pressure fuel in the pressure accumulator directly into a combustion chamber of an internal combustion engine, and an exhaust gas sensor for detecting a component in exhaust gas from the internal combustion engine.This fuel injection control device includes a timing setting unit configured to set a fuel injection timing in a second half of a compression stroke of the internal combustion engine when a component amount of a reduction target component in the exhaust gas detected by the exhaust gas sensor is greater than or equal to a predetermined value, under the condition that the internal combustion engine satisfies a predetermined high temperature condition at a predetermined calculation timing set for each combustion cycle of the internal combustion engine.This fuel injection control device further includes an injection control unit configured to calculate an injection period of fuel based on the injection timing set by the timing setting unit and to control the fuel injection valve based on the injection timing and the injection period.

[0018] According to the present disclosure, the injection timing in the second half of the compression stroke is set under the condition that the internal combustion engine satisfies the predetermined high-temperature condition when the component amount of the reduction target component in the exhaust gas detected by the exhaust gas sensor is greater than or equal to the predetermined value, that is, to desirably perform an operation to reduce the reduction target component. This configuration sets, as the condition that the internal combustion engine satisfies the predetermined high-temperature condition, the condition to implement injection in the second half of the compression stroke, thereby making it possible to avoid implementing fuel injection in the second half of the compression stroke in a case where the reduction target component is in the exhaust.Exhaust gas tends to be increased due to the implementation of fuel injection in the second half of the compression stroke. Short description of the drawings

[0019] The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description made with reference to the accompanying drawings. In the drawings: Is Fig. 1 is a schematic diagram showing a fuel injection system according to an embodiment, is Fig. 2 is a system block diagram showing an ECU which is a fuel injection control device according to the embodiment, is Fig. 3 is a view showing a relationship between an injection start timing of fuel into an internal combustion engine and a number of particulates in the exhaust gas, is Fig. 4 is a view showing the injection start timing of fuel into the internal combustion engine and a concentration of unburned fuel in the exhaust gas, and is in Fig. 5 is a flowchart showing fuel injection control according to the embodiment. Description of embodiments

[0020] As it is in Fig. As shown in Fig. 1, a fuel injection system 1 is a system configured to inject high-pressure fuel stored in a pressure accumulator 32 from a direct-injection fuel injection valve 30 into a combustion chamber of an internal combustion engine 10. The internal combustion engine 10 is a multi-cylinder, in-cylinder injection-type internal combustion engine that implements an intake stroke, a compression stroke, a combustion stroke, and an exhaust stroke as one combustion cycle. The pressure accumulator 32 is a supply pipe and stores high-pressure fuel supplied under pressure from 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 a pressure (fuel pressure) of fuel in the accumulator 32.

[0021] The fuel injection system 1 further includes a port injection valve 31 that injects fuel into an intake port 20 of the internal combustion engine 10. Fuel is supplied from the low-pressure pump 34 directly to the port injection valve 31 without passing through the high-pressure pump 33.

[0022] An intake air flow rate sensor 13 for detecting a flow rate of intake air and an intake air temperature sensor 14 are provided on the upstream side of an intake pipe 12 of the internal combustion engine 10. A throttle valve 16, an opening of which is adjusted using a motor 15, and a throttle opening sensor 17 for detecting the opening (throttle opening) of the throttle valve 16 are provided on the downstream side thereof.

[0023] A surge tank 18 is provided on the downstream side of the throttle valve 16, and an intake pipe pressure sensor 19 that detects pressure in the intake pipe is provided in the surge tank 18. The intake port 20 for introducing air into a combustion chamber 21 of each cylinder of the internal combustion engine 10 is connected to the surge tank 18. An electromagnetic fuel injection valve 30 that directly injects fuel into the combustion chamber 21 of each cylinder of the internal combustion engine 10 is attached to the cylinder. A spark plug 22 (an example of an ignition mechanism) is attached to a cylinder head 11B of each of the cylinders, and the air-fuel mixture in the combustion chamber 21 is ignited using a spark discharge from the spark plug 22 of the cylinder.

[0024] An exhaust pipe 23 of the internal combustion engine 10 is provided with an A / F sensor 24 that detects an air-fuel ratio of exhaust gas. A catalyst stage 25 and a particulate removal stage 35 are provided downstream of the A / F sensor 24. The catalyst stage 25 is a stage that includes an exhaust gas purification catalyst, such as a three-way catalyst (3-way catalyst). The particulate removal stage 35 is a stage that primarily removes particulate matter in the exhaust gas. The particulate removal stage 35 is, for example, a gasoline particulate filter (GPF) and a 4-way GPF in which a catalyst is supported on the GPF. A PM sensor 36 that detects the concentration of particulate matter (PM) in the exhaust gas is provided on the downstream side of the particulate matter removal stage 35.The A / F sensor 24 and the PM sensor 36 are examples of an exhaust gas sensor that detects an amount of a predetermined component contained in the exhaust gas. A NOx sensor, an O2 sensor, and / or the like may be used instead of or in addition to the A / F sensor 24 and the PM sensor 36.

[0025] A water temperature sensor 26 that detects a cooling water temperature and a knock sensor 27 that detects knocking are mounted on a cylinder block 11A of the internal combustion engine 10. A crank angle sensor 29 that outputs a pulse signal every time a crankshaft 28 rotates by a predetermined crank angle is mounted on an outer peripheral side of the crankshaft 28. A crank angle and an engine rotation speed are detected based on a crank angle signal from the crank angle sensor 29. Furthermore, the combustion chamber 21 may be provided with a fuel chamber pressure sensor that detects a pressure in the combustion chamber 21 and a combustion chamber temperature sensor that detects the temperature in the combustion chamber 21.

[0026] The outputs from those various sensors are fed to an ECU 40. The ECU 40 is an electronic control unit primarily including a microcomputer and implements various controls of the internal combustion engine 10 using detection signals from the various sensors. The ECU 40 calculates a fuel injection amount according to an engine operating state of the internal combustion engine 10 to control fuel injection of the fuel injection valve 30 and to control ignition timing of the spark plug 22.

[0027] As it is in Fig. 2, the ECU 40 includes a load calculation unit 41, an exhaust component acquisition and calculation unit 42, a timing setting unit 43, a storage unit 44, an injection control unit 45, and a pump control unit 46.

[0028] The load calculation unit 41 calculates an operating load and a rotational speed of the internal combustion engine 10 based on detection values ​​of the intake air flow sensor 13, the intake air temperature sensor 14, and the crank angle sensor 29. The detection 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 exhaust component acquisition and calculation unit 42.

[0029] The exhaust component acquisition and calculation unit 42 acquires the detection values ​​from the A / F sensor 24, the PM sensor 36, and the water temperature sensor 26, and calculates an amount of a predetermined component contained in the exhaust gas. The predetermined component to be calculated is a reduction target component that is preferentially reduced in the exhaust gas. Specifically, the predetermined component includes, for example, unburned fuel, components such as oxygen that are indicators of the combustion state (the lower the component amount, the better the combustion state), particulate matter, harmful components such as NOx, and the like.The detection values ​​of the various sensors obtained by the exhaust gas component acquisition and calculation unit 42 and the calculated component amount of the predetermined component in the exhaust gas are output to the storage unit 44 together with the data supplied from the load calculation unit 41.

[0030] The storage unit 44 stores the operating load and rotation speed of the internal combustion engine 10 calculated by the load calculation unit 41, and a component amount of the predetermined component contained in the exhaust gas calculated by the exhaust component acquisition and calculation unit 42. More specifically, the storage unit 44 stores, as a map or a formula, a relationship between the timing of actual fuel injection (injection implementation timing) and the component amount of the reduction target component contained in the exhaust gas for each of the operating load and rotation speed of the internal combustion engine 10 at the same time.

[0031] For example, the storage unit 44 stores, as a first component amount, the component amount of the reduction target component in the exhaust gas when the injection implementation timing is in the second half of the compression stroke. For example, the storage unit 44 stores, as the second component amount, the component amount of the reduction target component in the exhaust gas when the injection implementation timing is in the intake stroke or in the first half of the compression stroke.

[0032] The timing setting unit 43 determines the injection timing of fuel injected from the fuel injection valve 30 and the terminal injection valve 31 at a predetermined calculation timing set for each combustion cycle of the internal combustion engine 10. More specifically, the timing setting unit 43 determines whether to set the injection timing in the second half of 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, an operation history, and the detection values ​​of sensors 50. The timing setting unit 43 can set the ignition timing of fuel according to the injection timing.

[0033] As it is in Fig. 3 and Fig. As can be seen from Fig. 4, when the fuel injection timing is in the intake stroke of the internal combustion engine 10 and in the second half of the compression stroke, the number of particulates and the amount of unburned fuel in the exhaust gas of the internal combustion engine 10 are low. When fuel injection is implemented in the second half of the compression stroke of the internal combustion engine 10, fuel injected into the high-temperature combustion chamber 21 is quickly vaporized, thereby expectedly making it possible to improve the combustion state to make it possible to reduce harmful components in the exhaust gas. Whether the fuel injection timing is set in the intake stroke or the second half of the compression stroke to further reduce the reduction target component in the exhaust gas depends on the operating state of the internal combustion engine 10.

[0034] The timing setting unit 43 determines whether or not the inside of the combustion chamber 21 of the internal combustion engine 10 satisfies a predetermined high-temperature condition based on the load and rotation speed of the internal combustion engine 10, the detection values ​​of the sensors 50, and the like. Upon determining that the inside of the combustion chamber 21 satisfies the predetermined high-temperature condition, the timing setting unit 43 sets the injection timing in the second half of the compression stroke of the internal combustion engine 10. Note that the predetermined high-temperature condition is a condition in which the inside of the combustion chamber 21 is in a high-temperature state in the second half of the compression stroke, so that the amount of the reduction target component becomes less than a predetermined value.The predetermined high temperature condition may be set based on the operation history of the internal combustion engine 10 or an operation history obtained in another internal combustion engine having an equivalent structure to the internal combustion engine 10.

[0035] The timing setting unit 42 refers to a map or the like stored in the ECU 40 and determines whether or not the predetermined high-temperature condition is satisfied. The ECU 40 stores a map or a mathematical equation. The map or the mathematical equation relates the operating state of the engine 10, the detection values ​​of the sensors 50, and various parameters calculated from the detection values ​​to the temperature and pressure in the engine 10 in the second half of the compression stroke and the component amount of the reduction target component. A predetermined numerical range that satisfies the high-temperature condition can be set based on the map or the equation stored.which are stored in the ECU 40 for each of the data, operating state of the internal combustion engine 10, detection values ​​of the sensors 50 and various parameters calculated from the detection values.

[0036] The timing setting unit 43 can determine that the inside of the combustion chamber 21 satisfies the predetermined high temperature condition in a case where the detection values ​​are respectively within predetermined numerical ranges that are appropriately set. The detection values ​​are, for example, the intake air temperature detected by the intake air temperature sensor 14, the cooling water temperature of the engine 10 detected by the water temperature sensor 26, the rotation speed of the engine 10 and the load of the engine 10 calculated from the detection value of the crank angle sensor 29, and the fuel pressure detected by the fuel pressure sensor 37.

[0037] Alternatively, the fuel injection system 1 may be configured to detect or calculate a compression ratio, an internal EGR (Exhaust Gas Recirculation) amount, an external EGR amount, an external EGR temperature, and the like. In this case, the timing setting unit 43 may determine that the inside of the combustion chamber 21 satisfies the predetermined high-temperature condition in a case where those detection values ​​are respectively within numerical ranges that are appropriately set. The compression ratio and the internal EGR amount may be calculated from control variables of an intake variable valve timing (VCT) mechanism, an intake variable valve lift (VVL) mechanism, and a variable compression ratio (VCR) mechanism.The external EGR amount and the external EGR temperature can be detected using a flow rate sensor and a temperature sensor installed in an external EGR pipe through which exhaust gas flows from the exhaust system into the intake system of the internal combustion engine 10.

[0038] The timing setting unit 43 may be further configured to set the fuel injection timing in the second half of the compression stroke of the internal combustion engine 10 under the condition that the fuel pressure in the pressure accumulator 32 detected by the fuel pressure sensor 37 is equal to or higher than a predetermined value. This configuration makes it possible to restrict fuel injection at a low fuel pressure, thereby limiting an increase in the amount of the reduction target component (e.g., PM and unburned fuel) in the exhaust gas due to enlarged fuel droplets and insufficient evaporation.

[0039] In a configuration in which the injection timing is set in the second half of the compression stroke, the timing setting unit 43 can set an optimal injection timing that makes it possible to further reduce the component amount of the reduction target component in the exhaust gas and reduce fuel consumption.

[0040] More specifically, for example, in a configuration to perform homogeneous combustion, the temperature in the combustion chamber 21 is increased as much as possible by compressing the volume of the combustion chamber. Furthermore, in order to promote fuel atomization, the injection timing is retarded as much as possible within a range where homogeneity can be ensured in the combustion chamber 21. In a case where the injection timing is excessively retarded, fuel spray will be deviated in the combustion chamber 21, which is reduced in volume, and therefore, a mixture (mixture of air and fuel) will hardly be formed.

[0041] Furthermore, for example, in the case of performing stratified charge combustion, the fuel injection timing is adjusted so that an air-fuel mixture is formed in a predetermined air-fuel ratio near the spark plug 22 at the fuel ignition timing set for each operating condition.

[0042] The timing setting unit 43 may further set the injection implementation timing in which the component amount of the reduction target component is small as the injection implementation timing of the next combustion cycle, with reference to a map or the like stored in the storage unit 44. The map or the like defines a relationship between the injection implementation timing and the component amount of the reduction target component in the exhaust gas.

[0043] For example, the timing setting unit 43 refers to a map or the like stored in the storage unit 44 and defines the relationship between the injection implementation timing and the component amount of the reduction target component in the exhaust gas for the load and the rotation speed set according to the operating load and the rotation speed of the internal combustion engine 10 calculated by the load calculation unit 41.The timing setting unit 43 reads a component amount of the reduction target component (first component amount) in the exhaust gas when the injection implementation timing is in the second half of the compression stroke, and a component amount of the reduction target component (second component amount) in the exhaust gas when the injection implementation timing is in the intake stroke or the first half of the compression stroke, and compares the first component amount with the second component amount. If the first component amount is equal to or less than the second component amount (first component amount ≤ second component amount), the timing setting unit 43 sets the injection timing to the second half of the compression stroke under the condition that the inside of the combustion chamber 21 satisfies a predetermined high temperature condition.Conversely, when the first component amount exceeds the second component amount (first component amount > second component amount), the timing setting unit 43 sets the injection timing in the intake stroke or the first half of the compression stroke.

[0044] The determination based on the relationship between the injection implementation timing and the component amount of the reduction target components in the exhaust gas stored in the storage unit 44 may be performed before or after the determination of whether or not the inside of the combustion chamber 21 satisfies the predetermined high temperature condition.

[0045] The timing setting unit 43 determines, if necessary, whether to implement multiple split injections during one combustion cycle of the internal combustion engine 10 and sets the injection timing of each injection in the split injections. In this case, it is preferable to set the injection timing of the last injection at the end of the multiple split injections to be performed in the second half of the compression stroke of the internal combustion engine 10. The split injection may be performed for the purpose of, for example, assisting ignition of fuel or supplying an air layer between injections of fuel into the combustion chamber 21.

[0046] When implementing split injection, fuel may be injected using only the fuel injection valve 30, or fuel may be injected using the fuel injection valve 30 and the port injection valve 31 in combination. In the latter case, the injection start timing of the port injection valve 31 is preferably set in a period from the time immediately before the intake valve of the internal combustion engine 10 is closed in the combustion cycle of the internal combustion engine 10 to the end of the intake stroke of the current combustion cycle of the internal combustion engine 10. The injection start timing of the fuel injection valve 30 is preferably set in the second half of the compression stroke of the current combustion cycle of the internal combustion engine 10.

[0047] It is preferable that the timing setting unit 43 sets the injection timing of the injection implemented at the end among the multiple divided injections during one combustion cycle of the internal combustion engine 10, in the second half of the compression stroke of the internal combustion engine 10. Furthermore, it is further preferable to set the injection timing of the last injection implemented in the second half of the compression stroke of the internal combustion engine 10 and before the ignition of fuel, so that a rich air-fuel mixture can be formed around the spark plug 22 by the last injection.

[0048] The timing setting unit 43 may reset the injection timing based on the detection values ​​obtained from various fuel injection timing sensors. For example, the timing setting unit 43 may set the injection timing in the second half of the compression stroke at a predetermined calculation timing set for each combustion cycle of the internal combustion engine 10, and may then obtain the pressure and temperature in the combustion chamber 21, the component amount of the reduction target component in the exhaust gas, and the like when the second half of the compression stroke is reached, and further reset the previously set injection timing based on the detection values.

[0049] The timing setting unit 43 may be configured to set a prohibition flag to prohibit fuel injection in the second half of the compression stroke of the internal combustion engine 10 based on a component amount of a predetermined component in the exhaust gas obtained while the fuel injection is performed in the second half of the compression stroke.More specifically, the timing setting unit 43 sets the prohibition flag to prohibit fuel injection in the second half of the compression stroke of the internal combustion engine 10 under the condition that a component amount of the predetermined component in the exhaust gas obtained by acquiring the detection values ​​from the A / F sensor 24 and the PM sensor 36 in the second half of the compression stroke, or a component amount of a predetermined component in the exhaust gas calculated by the acquiring and calculating unit 42 based on the detection values, is equal to or greater than a predetermined threshold value. The threshold value set for the amount of the predetermined component in the exhaust gas may be mapped according to the injection timing, the temperature and pressure in the combustion chamber 21 of the internal combustion engine 10, and the rotational speed.The speed and load of the internal combustion engine 10 can be stored in a storage unit of the ECU 40.

[0050] The timing setting unit 43 may set the prohibition flag when the injection control cannot be accurately implemented and therefore it is predicted that the amount of the predetermined component in the exhaust gas will increase if fuel injection is performed in the second half of the compression stroke. For example, the flag prohibiting fuel injection in the second half of the compression stroke may be set when an abnormality is detected in the fuel system, when fail-safe control is performed, when the rotation speed of the internal combustion engine 10 is equal to or higher than a predetermined value and therefore the injection cannot be completed before the ignition timing, and the like.

[0051] The timing setting unit 43 may permit fuel injection in the second half of the compression stroke when the components to be reduced in the exhaust gas detected by the exhaust gas sensor exceed a predetermined value in a case where fuel is injected from the fuel injection valve 30 into the combustion chamber 21 at a timing other than the second half of the compression stroke (for example, in the intake stroke or the second half of the compression stroke). The prohibition flag may be canceled instead of permitting fuel injection in the second half of the compression stroke. Further, the timing setting unit 43 may be configured to cancel the prohibition flag when the above-mentioned prohibition flag setting condition is no longer satisfied. Alternatively, a condition to cancel the prohibition flag may be provided separately from the condition to set the prohibition flag.

[0052] The timing setting unit 43 may be configured to switch the injection mode based on the component amount of the reduction target component in the exhaust gas detected during implementation of the fuel injection. For example, the injection mode (e.g., a second-half compression stroke injection mode) being implemented may be switched to another injection mode under the condition that the detected amount of the reduction target component in the exhaust gas is equal to or greater than a predetermined value. For example, the injection mode may be switched by setting and releasing the prohibition flag.

[0053] The injection control unit 45 calculates the fuel injection period based on the fuel injection timing set by the timing setting unit 43, and controls the fuel injection valve 30 or the port injection valve 31 based on the injection timing and the injection period to implement fuel injection. The fuel injection valve 30 is controlled so that fuel is injected only in the second half of the compression stroke of the internal combustion engine 10 when the injection timing is set by the timing setting unit 43 in the second half of the compression stroke of the internal combustion engine 10.

[0054] The injection control unit 45 calculates the injection period of combustion based on the start of the injection timing (injection start timing) set by the timing setting unit 43, the fuel ignition timing, and the rotation speed of the internal combustion engine 10. The injection control unit 45 controls the fuel injection valve 30 or the terminal injection valve 31 based on the injection start timing and the injection period to inject fuel into the combustion chamber 21. When the prohibition flag is set by the timing setting unit 43 and when fuel injection is implemented in the second half of the compression stroke, the injection control unit 45 causes the fuel injection valve 30 or the terminal injection valve 31 to stop injection.

[0055] The injection control unit 45 may further calculate the fuel injection amount based on the fuel injection period and the fuel pressure. The calculated injection amount may be mapped or mathematically associated with the target reduction component in the exhaust gas and stored in the storage unit of the ECU 40.

[0056] The fuel injection amount in the second half of the compression stroke is preferably set to an optimal injection amount that further enables the component amount of the reduction target component in the exhaust gas to be reduced and fuel consumption to be reduced. Specifically, it is preferable to set the injection amount as much as possible within a range in which homogeneity in the combustion chamber 21 can be ensured. Alternatively, the injection amount may be set within a range in which a target value set for the component amount of the reduction target component in the exhaust gas or fuel consumption (for example, a target value set according to a regulation value of the number of particulates in the exhaust gas) can be achieved.

[0057] Furthermore, for example, when stratified charge combustion is performed, the injection conditions such as the injection amount are preferably controlled so that the air-fuel mixture is formed in a predetermined air-fuel ratio in the vicinity of the spark plug 22 at the ignition timing of fuel set for each operating condition.

[0058] Furthermore, for example, for the purpose of reducing the injection amount of fuel as much as possible immediately before ignition in order to improve robustness, the injection control unit 45 may reduce the injection amount of fuel in the second half of the compression stroke within a range in which the exhaust gas amount can be the target value.

[0059] When implementation of the split injection is determined by the timing setting unit 43 and when the injection pattern of the split injection is set to perform injection of the second half of the compression stroke, the injection control unit 45 may calculate the injection period and may additionally calculate the injection amount for each injection.

[0060] The injection control unit 45 preferably controls the amount of fuel injected in each of multiple divided injections so that the amount of fuel injected in the second half of the compression stroke becomes larger than the amount of fuel injected in a stroke other than the second half of the compression stroke.

[0061] The injection control unit 45 may set the amount of fuel injected in each of the multiple split injections so that the amount of fuel injected in the second half of the compression stroke of the internal combustion engine 10 becomes larger than the amount of fuel injected in a stroke other than the second half of the compression stroke of the internal combustion engine 10, under the condition that the component amount of the reduction target component in the exhaust gas detected by the A / F sensor 24 or the PM sensor 36 is equal to or larger than a predetermined value.

[0062] In a case where the injection timing of the injection in the second half of the compression stroke and before the ignition of the fuel is set, it is preferable that the injection control unit 45 controls the injection state of the injection that is implemented last so that a rich air-fuel mixture is formed around the spark plug 22 to cause stratified combustion.

[0063] When the timing setting unit 43 resets the injection timing based on the detection values ​​obtained from various sensors at the time of fuel injection, the injection control unit 45 may calculate the injection period for the reset injection period, and may additionally calculate the injection amount.

[0064] The pump control unit 46 controls the output of the high-pressure pump 33 and the output of the low-pressure pump 34 based on the detection value of the fuel pressure sensor 37. The pump control unit 46 may be configured to set a target fuel pressure and allow fuel injection to be implemented under the condition that the detection value of the fuel pressure sensor 37 becomes a value close to the target fuel pressure. In a case where fuel is injected in the second half of the compression stroke when the fuel pressure is low, droplets of injected fuel may be generated and fuel vaporization may become insufficient. Consequently, the combustion state may be deteriorated, and the component amount of the reduction target component in the exhaust gas may be increased.Therefore, when the injection timing is set in the second half of the compression stroke, the target fuel pressure is set higher than when the injection timing is set in a different stroke, such as the intake stroke. Additionally, when the fuel pressure is high at the time of fuel injection, the initial velocity of fuel becomes faster and the injected fuel droplets become smaller. Therefore, the number of collisions between air molecules and fuel droplets per unit time increases, thereby allowing fuel to preferentially disperse and preferentially form a mixture of fuel and air.

[0065] The injection control process executed by the ECU 40 will be described with reference to the flowchart shown in Fig.5. First, in step S100, it is determined whether or not it is a set timing such as an injection timing. This set timing is a predetermined calculation timing set for each combustion cycle of the internal combustion engine 10.

[0066] If it is the set timing, the process proceeds to step S101, where the ECU 40 acquires the operating state of the engine 10 and sensor detection values ​​from various sensors. Specifically, detection values ​​such as the load of the engine 10, the detection value of an unburned fuel amount and the number of particulates in the exhaust gas detected by the A / F sensor 24 and the PM sensor 36, the cooling water temperature of the engine 10 from the water temperature sensor 26, the intake air flow rate from the flow rate sensor 13, the intake air temperature from the intake air temperature sensor 14, and the temperature in the combustion chamber 21 are acquired based on the crank angle signal from the crank angle sensor 29, if necessary.Furthermore, in a case where a fuel chamber pressure sensor, a combustion chamber temperature sensor, and the like are installed, the detection values ​​of the pressure and temperature in the combustion chamber 21 can be obtained.

[0067] The process proceeds to step S102, where it is determined whether a component amount of a predetermined reduction target component (for example, PM or unburned fuel) in the exhaust gas is equal to or more than a threshold X. If the component amount of the predetermined reduction target component is less than the threshold, the process proceeds to step S113 to determine to implement injection in an operation mode (non-second-half compression stroke injection mode) in which fuel injection is not implemented in the second half of the compression stroke. If the component amount of the predetermined reduction target component is equal to or more than the threshold, the process proceeds to step S103.

[0068] In step S103, the first component amount and the second component amount stored in the ECU 40 are compared to determine whether the first component amount is equal to or less than the second component amount (first component amount ≤ second component amount). The first component amount is the component amount of the reduction target component in the exhaust gas when the injection implementation timing is in the second half of the compression stroke, and the second component amount is the amount of the reduction target component in the exhaust gas when the injection implementation timing is in the intake stroke or in the first half of the compression stroke.That is, the first component amount is a component amount of the reduction target component in the exhaust gas detected when actual injection is implemented in the operation mode (second-half compression stroke injection mode) in which fuel injection is implemented in the second half of the compression stroke. The second component amount is a component amount of the reduction target component in the exhaust gas detected when actual injection is performed in the non-second-half compression stroke injection mode. In a case where the first component amount > the second component amount, the process proceeds to step S113, where a determination is made to perform the injection in the non-second-half compression stroke injection mode. If the first component amount ≤ the second component amount, the process proceeds to step S104.

[0069] In step S104, the ECU 40 determines whether or not the inside of the combustion chamber 21 satisfies the predetermined high-temperature condition based on the acquired operating state and the sensor detection values ​​of the various sensors. Specifically, it is determined that the inside of the combustion chamber 21 satisfies the predetermined high-temperature condition when the detection value, such as the intake air temperature detected by the intake air temperature sensor 14, the cooling water temperature of the engine 10 detected by the water temperature sensor 26, the rotation speed or load of the engine 10 calculated from the detection value from the crank angle sensor 29, and the fuel pressure detected by the fuel pressure sensor 37, is within a predetermined numerical range that is appropriately set.When the inside of the combustion chamber 21 satisfies the predetermined high temperature condition, the process proceeds to step S105.

[0070] In step S104, if the inside of the combustion chamber 21 does not satisfy the predetermined high temperature condition, the process proceeds to step S111, where it is determined whether or not to implement a high temperature process for the temperature inside the combustion chamber 21. For example, when the internal combustion engine 10 is cold-started, it is determined that the predetermined high temperature condition of step S104 is not satisfied, however, the high temperature process may be executed to satisfy the predetermined high temperature condition.

[0071] Specifically, the process of the high-temperature process may include, for example, increasing the compression ratio of the variable compression ratio mechanism, preventing late closing and early opening of the intake WT, adjusting intake temperature cooling to increase the intake temperature, switching the cooling system of the internal combustion engine 10 to heat the combustion chamber 21 with cooling recirculation water, increasing the internal EGR amount or the external EGR amount of the internal combustion engine 10, and the like. When the high-temperature process is being executed, the process returns from step S112 to step S104. When the high-temperature process is not being executed, the process proceeds from step S111 to step S113 to determine to implement injection in the non-second-half compression stroke injection mode.

[0072] In step S105, it is determined whether the fuel pressure in the pressure accumulator 32, obtained from the fuel pressure sensor 37, is within a predetermined range with respect to the target fuel pressure P1. Specifically, for example, it is determined whether P1-ΔP1 ≤ P ≤ P1+ΔP1. If the fuel pressure is within the predetermined range, the process proceeds to step S106 to determine whether to implement fuel injection in the second half of the compression stroke.That is, under the condition that the component amount of the reduction target component in the exhaust gas is equal to or more than the threshold value X, that the measured first component amount is equal to or less than the second component amount, that the internal combustion engine 10 satisfies the predetermined high temperature condition suitable for fuel injection in the second half of the compression stroke, and that the fuel pressure in the pressure accumulator 32 is within the predetermined range with respect to the target fuel pressure, the ECU 40 uses the second-half compression stroke injection mode and sets the fuel injection timing to the second half of the compression stroke of the internal combustion engine 10.When the fuel pressure in the pressure accumulator 32 is not within the predetermined range with respect to the target fuel pressure, the process proceeds to step S113 to determine to perform injection in the non-second-half compression stroke injection mode.

[0073] In steps S107 to S110, the process is executed to implement injection in the second half of the compression stroke injection mode. First, in step S107, it is determined whether or not injection is implemented in a stroke (for example, the intake stroke) other than the second half of the compression stroke. That is, it is determined whether or not the split injections are implemented. If injection is implemented in another stroke, the process proceeds to step S108, where the injection period and the injection amount are calculated based on the set injection timing for fuel injection implemented in another stroke, and the process proceeds to step S109. If injection is not implemented in another stroke, the process proceeds directly from step S107 to step S109.

[0074] In step S109, the fuel injection timing and ignition timing are calculated. Specifically, the injection timing is calculated based on the load of the internal combustion engine 10, the acquired detection values ​​of the unburned fuel amount, and the number of particulates with reference to the injection timing and injection amount map stored in the ECU 40.

[0075] In a case where the port injection valve 31 is additionally used for fuel injection, the injection start timing of the port injection valve 31 is set to a period after the intake valve of the internal combustion engine 10 is closed in the combustion cycle of the internal combustion engine 10, immediately before and before the end of the intake stroke of the current combustion cycle of the internal combustion engine 10, and the injection start timing of the fuel injection valve 30 is set to the second half of the compression stroke of the current combustion cycle of the internal combustion engine 10.

[0076] Next, the process proceeds to step S110, where the fuel injection amount of the fuel injection implemented in the second half of the compression stroke is calculated. The injection period and injection amount for the fuel injection performed in the second half of the compression stroke are calculated based on the calculated injection timing and the fuel pressure detection value.

[0077] In addition, when the component amount of the reduction target component in the exhaust gas detected by the A / F sensor 24, the PM sensor 36, and the like is equal to or more than the predetermined value, the amount of fuel injected in the second half of the compression stroke of the internal combustion engine 10 may be set to be larger than the amount of fuel injected in a stroke other than the second half of the compression stroke of the internal combustion engine 10.

[0078] On the other hand, in steps S113 to S115, the process is executed to execute injection in the non-second-half compression stroke injection mode. In step S113, if it is determined to implement injection in the non-second-half compression stroke injection mode, the process then proceeds to steps S114 and S115 in this order to set the fuel injection timing, the fuel ignition timing, and the fuel injection amount at each injection timing. Consequently, the process proceeds to step S116.

[0079] If it is determined in step S116 that the set injection timing has been reached, the process proceeds to step S117, where fuel injection is implemented, and the process proceeds to step S118. In step S118, it is determined whether the component amount of the reduction target component in the exhaust gas is equal to or less than a predetermined threshold value Y. The process is performed immediately after step S117, where injection is implemented. Therefore, in step S118, the component amount of the reduction target component in the exhaust gas, which is obtained based on the detection values ​​of the various sensors when the injection is performed, is compared with the threshold value Y.

[0080] When the component amount of the reduction target component exceeds the threshold Y, the process proceeds to step S119 to determine whether to switch the injection mode. When the injection is implemented in the second-half compression stroke injection mode, it is determined to switch to the non-second-half compression stroke injection mode. When the injection is implemented in the non-second-half compression stroke injection mode, it is determined to switch to the second-half compression stroke injection mode. The injection mode can be switched by setting a flag that prohibits the injection mode from being implemented.

[0081] The process proceeds from step S119 to step S120. Further, when the component amount of the reduction target component is equal to or less than the threshold value Y in step S118, the process proceeds to step S120. In step S120, the ECU 40 acquires and stores the detection value (specifically, the detection values ​​from the A / F sensor 24 and the P sensor 36) of the component amount of the reduction target component in the exhaust gas from the injection start timing to the injection end timing.

[0082] The embodiment described above produces the following effects.

[0083] The timing setting unit 43 sets the injection timing in the second half of the compression stroke when the component amount of the reduction target component in the exhaust gas detected by the exhaust gas sensor such as the A / F sensor 24 and the PM sensor 36 is equal to or greater than the predetermined value, under the condition that the inside of the combustion chamber 21 of the internal combustion engine 10 satisfies the predetermined high-temperature condition (under the condition that the inside of the combustion chamber 21 is in the high-temperature state in the second half of the compression stroke, so that the reduction target component amount becomes less than the predetermined value). Therefore, implementing fuel injection in the second half of the compression stroke makes it possible to restrict the reduction target component in the exhaust gas from increasing.

[0084] The storage unit 44 stores, for each load and each rotation speed of the internal combustion engine 10, the relationship between the injection implementation timing and the component amount of the reduction target component in the exhaust gas at that time as a map or a mathematical equation.

[0085] Specifically, the storage unit 44 stores, as the first component amount, the component amount of the reduction target component in the exhaust gas when the injection implementation timing is in the second half of the compression stroke. Specifically, the storage unit 44 stores, as the second component amount, the component amount of the reduction target component in the exhaust gas when the injection implementation timing is in the intake stroke or in the first half of the compression stroke. Then, the timing setting unit 43 reads the first component amount and the second component amount with reference to the map stored in the storage unit 44. When the first component amount ≤ the second component amount, the injection timing is set in the second half of the compression stroke under the condition that the inside of the combustion chamber 21 satisfies the predetermined high temperature condition.When the first component amount > the second component amount, the timing setting unit 43 sets the injection timing in the intake stroke or the first half of the compression stroke. When fuel is actually injected into the internal combustion engine 10, this configuration compares the component amount with the predetermined reduction target component obtained by the exhaust gas sensor and selects the injection mode implemented for the internal combustion engine 10, thereby enabling the injection timing to be set so that the reduction target component in the exhaust gas can be further reduced.

[0086] The timing setting unit 43 prohibits fuel injection in the second half of the compression stroke under the condition that the component amount of the reduction target component in the exhaust gas detected by the exhaust gas sensor during fuel injection from the fuel injection valve 30 into the combustion chamber 21 in the second half of the compression stroke is equal to or greater than the predetermined value. Furthermore, the timing setting unit 43 permits fuel injection in the second half of the compression stroke under the condition that the component amount of the reduction target component in the exhaust gas detected by the exhaust gas sensor when fuel is injected from the fuel injection valve 30 into the combustion chamber 21 in a stroke other than the second half of the compression stroke (for example, the intake stroke or the first half of the compression stroke) exceeds the predetermined value.Therefore, the configuration allows the injection mode to be switched when the component amount of the reduction target component increases due to the selected injection mode. The configuration allows the injection mode to be selected that is more appropriate depending on the operating state of the internal combustion engine 10 to further reduce the reduction target component in the exhaust gas.

[0087] The timing setting unit 43 sets the fuel injection timing in the second half of the compression stroke of the internal combustion engine 10 under the condition that the fuel pressure in the pressure accumulator 32 detected by the fuel sensor 37 is equal to or higher than the predetermined value. This configuration makes it possible to restrict fuel injection to a low fuel pressure, thereby limiting an increase in the amount of the reduction target component (e.g., PM and unburned fuel) in the exhaust gas due to enlarged fuel droplets and insufficient evaporation.

[0088] When the injection timing of at least one of the split injections is set in the second half of the compression stroke of the internal combustion engine 10, the injection control unit 45 sets the amount of fuel injected in the second half of the compression stroke of the internal combustion engine 10 to be larger than the amount of fuel injected in a stroke other than the second half of the compression stroke of the internal combustion engine 10, under the condition that the component amount of the reduction target component in the exhaust gas detected by the A / F sensor 24, the PM sensor 36, and the like is equal to or larger than the predetermined value.When the amount of the reduction target component in the exhaust gas is large, this configuration controls to increase the injection amount of fuel injected in the second half of the compression stroke and to implement fuel injection, thereby making it possible to reduce the component amount of the reduction target component in the exhaust gas according to the operating state of the internal combustion engine 10.

[0089] As above, the internal combustion engine 10 in which the injection valve 31 and the direct injection type fuel injection valve 30 are provided together has been described as an example. Note that the internal combustion engine having only the direct injection type fuel injection valve 30 may be used.

[0090] The fuel injection control device of the present disclosure can be applied to a diesel engine as well as a gasoline engine. That is, 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.

[0091] Although the present disclosure has been described in accordance with the examples, it is understood that the present disclosure is not limited to such examples or structures.

Claims

[1] A fuel injection control device (40) configured to control a fuel injection system (1), the fuel injection system including an accumulator (32) configured to store a high-pressure fuel, a direct injection fuel injection valve (30) configured to inject a high-pressure fuel in the pressure accumulator directly into a combustion chamber (21) of an internal combustion engine (10), and an exhaust gas sensor (24, 36) configured to detect a component in the exhaust gas from the internal combustion engine, the fuel injection control device comprising: a timing setting unit (43) configured to set a fuel injection timing in a second half of a compression stroke of the internal combustion engine when a component amount of a reduction target component in the exhaust gas detected by the exhaust gas sensor is greater than or equal to a predetermined value, under the condition that the internal combustion engine satisfies a predetermined high temperature condition at a predetermined calculation timing set for each combustion cycle of the internal combustion engine, and an injection control unit (45) configured to calculate an injection period of fuel based on the injection timing set by the timing setting unit, and to control the fuel injection valve based on the injection timing and injection period. [2] The fuel injection control device according to claim 1, wherein the timing setting unit is configured to prohibit injection of fuel in the second half of the compression stroke of the internal combustion engine when the fuel injection valve injects fuel into the combustion chamber in the second half of the compression stroke of the internal combustion engine, under the condition that the component amount of the reduction target component in the exhaust gas detected by the exhaust gas sensor is greater than or equal to the predetermined value. [3] A fuel injection control device according to claim 1 or 2, further comprising: a storage unit (44), wherein the storage unit is configured for each load and each speed of the combustion engine, to store a first component amount which is a component amount of the reduction target component in the exhaust gas detected by the exhaust gas sensor when the fuel injection valve injects fuel into the combustion chamber in the second half of the compression stroke of the internal combustion engine, and to store a second component amount which is a component amount of the reduction target component in the exhaust gas detected by the exhaust gas sensor when the fuel injection valve injects fuel into the combustion chamber in a stroke other than the second half of the compression stroke of the internal combustion engine, and the timing unit is configured for a predetermined load and a predetermined speed of the internal combustion engine, to compare the first component set with the second component set in the storage unit, to set the fuel injection timing in the second half of the compression stroke of the internal combustion engine when the component amount of the first component is less than or equal to the component amount of the second component, and to set the fuel injection timing in a stroke other than the second half of the compression stroke of the internal combustion engine when the component amount of the first component is larger than the component amount of the second component. [4] Fuel injection control device according to one of claims 1 to 3, wherein the timing setting unit is configured to permit fuel injection in the second half of the compression stroke of the internal combustion engine when the component amount of the reduction target component in the exhaust gas detected by the exhaust gas sensor is greater than the predetermined value in a case where the fuel injection valve injects fuel into the combustion chamber in a stroke other than the second half of the compression stroke of the internal combustion engine. [5] Fuel injection control device according to one of claims 1 to 4, wherein the fuel injection system further includes a fuel pressure sensor (37) configured to detect a fuel pressure in the accumulator, and the timing setting unit is configured to set the fuel injection timing in the second half of the compression stroke of the internal combustion engine under the condition that the fuel pressure detected by the fuel pressure sensor is equal to or higher than a predetermined value. [6] Fuel injection control device according to one of claims 1 to 5, wherein the time setting unit is configured, to set the injection timing so that a plurality of split injections are implemented during one combustion cycle of the internal combustion engine, and to set the injection timing of the last injection implemented at one end of the plurality of split injections in the second half of the compression stroke of the internal combustion engine. [7] The fuel injection control device according to claim 6, wherein the injection control unit is configured to set an amount of fuel injected in each of the plurality of divided injections so that the amount of fuel injected in the second half of the compression stroke of the internal combustion engine becomes larger than the amount of fuel injected in a stroke other than the second half of the compression stroke of the internal combustion engine, under the condition that the component amount of the reduction target component in the exhaust gas detected by the exhaust gas sensor is larger than or equal to a predetermined value. [8] Fuel injection control device according to claim 6 or 7, wherein the internal combustion engine further includes an ignition mechanism (22) configured to ignite fuel in the combustion chamber, the timing setting unit is configured to set the injection timing of the last injection to be implemented before ignition of fuel in the second half of the compression stroke, and the injection control unit is configured to control an injection state of the last injection so that a rich air-fuel mixture is formed around the ignition mechanism and stratified combustion takes place. [9] Fuel injection control device according to one of claims 1 to 8, wherein the internal combustion engine further includes a port injection valve (31) configured to inject high-pressure fuel in the accumulator into an intake port (20) of the internal combustion engine, and the timing unit is configured to, when fuel is injected using both the fuel injection valve and the terminal injection valve, to set an injection start timing of the terminal injection valve in a period of time after the intake valve of the internal combustion engine is closed in a combustion cycle of the internal combustion engine, which is immediately before the time before an intake stroke of the current combustion cycle ends, and to set an injection start timing of the fuel injection valve in the second half of the compression stroke of the current combustion cycle of the internal combustion engine.

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