Fuel injection control device for internal combustion engine and fuel injection control method for internal combustion engine

Abstract

The present application relates to a fuel injection control device of an internal combustion engine and a fuel injection control method of an internal combustion engine. The fuel injection control device, when performing split injection in which fuel is injected into a combustion chamber in a split manner into an intake stroke injection and a compression stroke injection, distributes and applies a correction value of a fuel injection amount for compensating for a deviation between a target value and a detected value of an air-fuel ratio, that is, an air-fuel ratio feedback correction value, to the intake stroke injection amount and the compression stroke injection amount. At the time of the distribution, the fuel injection control device makes a distribution rate of the air-fuel ratio feedback correction value to the compression stroke injection amount greater at the time of cold operation of the internal combustion engine than at the time of hot operation.

Description

Technical Field

[0001] This disclosure relates to a fuel injection control device and a fuel injection control method for an internal combustion engine. Background Technology

[0002] In internal combustion engines with in-cylinder injection, there are split-injection engines that inject fuel in multiple stages. Previously, Japanese Patent Application Publication No. 2014-173550 disclosed that an air-fuel ratio feedback correction value is set for each fuel injection in the split-injection process, and the closer the injection timing is to the piston top dead center, the smaller the air-fuel ratio feedback correction value becomes. The closer the injection timing is to the piston top dead center, the more fuel adheres to the piston, i.e., piston wetting. Furthermore, if piston wetting increases, the amount of PM (particulate matter) generated increases. Therefore, by reducing the air-fuel ratio feedback correction value by injecting fuel closer to the piston top dead center, the increase in PM generation can be suppressed.

[0003] However, in the cold-state operation of an internal combustion engine with low in-cylinder temperatures, fuel atomization is poor, resulting in a higher proportion of uncontributed fuel that does not contribute to combustion. Similar to hot-state operation, during this cold-state operation, the proportion of uncontributed fuel further increases when the air-fuel ratio feedback correction value is allocated to each fuel injection unit. This can potentially lead to deterioration of combustion conditions, increased fuel consumption, and worsened emissions. Summary of the Invention

[0004] According to a technical solution of this disclosure, a fuel injection control device for an internal combustion engine is provided. The internal combustion engine performs segmented injection, which injects fuel into the combustion chamber by dividing the injection into intake stroke injection and compression stroke injection. The fuel injection control device for the internal combustion engine includes a processing circuit configured to, during the segmented injection, allocate and apply a correction value for the fuel injection quantity, i.e., an air-fuel ratio feedback correction value, used to compensate for the deviation between the target value and the detected value of the air-fuel ratio, to the fuel injection quantity of the intake stroke injection and the fuel injection quantity of the compression stroke injection. Furthermore, when the internal combustion engine is operating in a cold state, the allocation rate of the air-fuel ratio feedback correction value to the fuel injection quantity of the compression stroke injection is increased compared to when the engine is operating in a hot state.

[0005] According to a technical solution of this disclosure, a fuel injection control method for an internal combustion engine is provided, comprising the steps of determining the fuel injection quantity during the intake stroke (i.e., the intake stroke injection quantity) and the fuel injection quantity during the compression stroke immediately following the intake stroke (i.e., the compression stroke injection quantity) according to the following formula: QC = SC·Q +W·LMB、QI=(1-SC)·Q +(1-W)·LMB Here, QC is the compression stroke injection quantity, QI is the intake stroke injection quantity, and the sum of QC and QI is the total amount of fuel to be supplied to the cylinder for a combustion event, Q The reference amount, i.e., the required injection amount, is the total amount of fuel to be supplied to the cylinder for the aforementioned combustion event. SC is a compression stroke segmentation coefficient greater than or equal to 0 and less than or equal to 1. LMB is an air-fuel ratio feedback correction value used to correct the reference amount based on the detected air-fuel ratio value obtained from the air-fuel ratio sensor. W is a weighting coefficient greater than or equal to 0 and less than or equal to 1. The weighting coefficient is 1 when the cylinder temperature, i.e., the in-cylinder temperature, is less than a first temperature. The weighting coefficient is 0 when the cylinder temperature is greater than a second temperature higher than the first temperature. When the cylinder temperature is greater than the first temperature and less than the second temperature, the weighting coefficient decreases from 1 to 0 as the cylinder temperature increases. The fuel injection control method further includes the following steps: injecting fuel of the determined intake stroke injection amount into the cylinder during the intake stroke; and injecting fuel of the determined compression stroke injection amount into the cylinder during the compression stroke.

[0006] According to a technical solution of this disclosure, a fuel injection control device for an internal combustion engine is provided. The internal combustion mechanism is configured to perform segmented fuel injection into the cylinder in such a manner that the sum of the fuel injection amount during the intake stroke (i.e., the intake stroke injection amount) and the fuel injection amount during the compression stroke immediately following the intake stroke (i.e., the compression stroke injection amount) is consistent with the total amount of fuel to be supplied to the cylinder for a combustion event. The fuel injection control device includes a processing circuit configured to perform the following steps: obtaining an air-fuel ratio feedback correction value during the segmented injection, the air-fuel ratio feedback correction value being a correction value for the fuel injection amount used to compensate for the deviation between a target value and a detected value of the air-fuel ratio; setting the allocation rate such that, during cold operation of the internal combustion engine, the allocation rate of the air-fuel ratio feedback correction value to the compression stroke injection amount is larger than that during hot operation; and allocating and applying the air-fuel ratio feedback correction value to the intake stroke injection amount and the compression stroke injection amount based on the allocation rate of the air-fuel ratio feedback correction value to the compression stroke injection amount. Attached Figure Description

[0007] Figure 1 This is a schematic diagram illustrating the structure of one embodiment of a fuel injection control device for an internal combustion engine.

[0008] Figure 2 Is Figure 1 A flowchart of the injection quantity allocation process performed in the fuel injection control device.

[0009] Figure 3It is a graph showing the relationship between the cylinder temperature and the weighting coefficient. Detailed Implementation

[0010] Hereinafter, an embodiment of the fuel injection control device for an internal combustion engine will be described in detail with reference to the accompanying drawings.

[0011] <Structure of the fuel injection control device for an internal combustion engine>

[0012] First, refer to Figure 1 The structure of the fuel injection control device for an internal combustion engine according to this embodiment will be described. The fuel injection control device of this embodiment is applied to an internal combustion engine 10 mounted in a vehicle.

[0013] like Figure 1 As shown, the internal combustion engine 10 includes a combustion chamber 11 for burning fuel. An intake passage 12, which provides the intake air for combustion, and an exhaust passage 13, which provides the exhaust gas generated by combustion, are connected to the combustion chamber 11. The combustion chamber 11 is a space formed within a cylinder. That is, the combustion chamber 11 is a space surrounded by the cylinder wall, piston, and cylinder head. An air flow meter 14, which detects the flow rate of the intake air flowing within it (i.e., the intake air volume GA), is provided in the intake passage 12. Additionally, a throttle valve 15, which adjusts the intake air volume GA by making the intake air flow path area variable, is provided in the intake passage 12. An in-cylinder injection valve 16, which injects fuel into the combustion chamber 11, is provided in the combustion chamber 11. Furthermore, an ignition device 17 is provided in the combustion chamber 11, which ignites the mixture of intake air introduced into the combustion chamber 11 through the intake passage 12 and fuel injected by the in-cylinder injection valve 16 via spark discharge. An air-fuel ratio sensor 18 is installed in the exhaust passage 13 to detect the air-fuel ratio of the mixture after combustion in the combustion chamber 11. In addition, an exhaust purification device 19 carrying a three-way catalytic converter is installed in the exhaust passage 13.

[0014] The internal combustion engine 10 is controlled by an Engine Control Module (ECM) 20. The ECM 20 includes a processing unit 21 and a storage unit 22. The storage unit 22 stores programs and data for controlling the internal combustion engine 10. The ECM 20 is configured to execute various processes for controlling the internal combustion engine 10 by the processing unit 21 executing the programs stored in the storage unit 22. The detection signals from the air flow meter 14 and the air-fuel ratio sensor 18 are input to the ECM 20. Additionally, detection signals from the crankshaft angle sensor 23 and the coolant temperature sensor 24 are also input to the ECM 20. The crankshaft angle sensor 23 detects the rotation angle θc of the output shaft (crankshaft) of the internal combustion engine 10. The coolant temperature sensor 24 detects the temperature of the coolant in the internal combustion engine 10, i.e., the engine coolant temperature THW. The ECM 20 calculates various operating parameters of the internal combustion engine 10 based on the detection results of these sensors. Examples of operable parameters include the throttle opening ratio (throttle valve 15), the ignition timing of the air-fuel mixture by the ignition device 17, and the timing and amount of fuel injection by the in-cylinder injection valve 16. Furthermore, based on the calculated operable parameters, the ECM 20 operates the throttle valve 15, the in-cylinder injection valve 16, the ignition device 17, etc., of the internal combustion engine 10, thereby controlling the internal combustion engine 10. It should be noted that the ECM 20 calculates the crankshaft speed (engine speed NE) based on the detected crankshaft angle θc. Additionally, the ECM 20 calculates the engine load rate KL based on the engine speed NE, the intake air volume GA, etc. The engine load rate KL represents the intake air filling rate of the combustion chamber 11.

[0015] <Overview of Fuel Injection Control>

[0016] The following is a summary of the fuel injection quantity control of the internal combustion engine 10 implemented by the ECM20. The ECM20 calculates the total injection quantity QT in each predetermined fuel injection quantity calculation cycle. The total injection quantity QT represents the amount of fuel injected to achieve the required injection quantity Q. The amount of fuel injected is indicated by the ECM20 to the in-cylinder injection valve 16. When calculating the total injection quantity QT, the ECM20 calculates, based on the engine load rate KL, the amount of fuel required to achieve the target air-fuel ratio of the mixture burned in the combustion chamber 11, as the required injection quantity Q. The value of Q. "Required injection volume Q" "The total fuel injection quantity (QT) is the reference amount, which is the total amount of fuel to be supplied to one cylinder for each combustion event. Each combustion event is usually generated by the ignition of the air-fuel mixture. The total amount of fuel to be supplied to one cylinder for each combustion event is obtained by correcting this reference amount as needed. In addition, the ECM 20 calculates the correction value of the fuel injection quantity, namely the air-fuel ratio feedback correction value (LMB), based on the detected air-fuel ratio value obtained by the air-fuel ratio sensor 18. The ECM 20 calculates the air-fuel ratio feedback correction value (LMB) by gradually updating the value in a way that reduces the deviation between the detected air-fuel ratio value and the target value. Then, the ECM 20 adjusts the required injection quantity QT according to the target value." The total injection quantity QT is calculated by adding the air-fuel ratio feedback correction value LMB (QT = Q +LMB). It should be noted that when ECM20 calculates the total injection quantity QT, it makes various corrections in addition to the air-fuel ratio feedback correction value LMB.

[0017] It should be noted that the ECM20 selectively executes either segmented injection (injecting fuel in the combustion chamber 11 by dividing it into intake stroke injection and compression stroke injection) or non-segmented injection (injecting fuel without segmentation). The ECM20 determines which type of injection to execute based on factors such as engine speed NE, engine load rate KL, and engine coolant temperature THW. Furthermore, during non-segmented injection, the ECM20 instructs the in-cylinder injection valve 16 to inject a total injection quantity QT of fuel starting from the injection timing determined according to the operating conditions of the internal combustion engine 10. Conversely, during segmented injection, the ECM20 allocates the total injection quantity QT into an intake stroke injection quantity QI and a compression stroke injection quantity QC. The intake stroke injection quantity QI represents the fuel injection quantity during the intake stroke, and the compression stroke injection quantity QC represents the fuel injection quantity during the compression stroke. Then, ECM20 instructs the in-cylinder injection valve 16 to inject fuel at the intake stroke injection quantity QI during the intake stroke and at the compression stroke injection quantity QC during the compression stroke.

[0018] <Split-jet injection quantity distribution processing>

[0019] Next, refer to Figure 2 and Figure 3 The injection quantity allocation process implemented by ECM20 in order to calculate the intake stroke injection quantity QI and the compression stroke injection quantity QC during split injection is explained. Figure 2 The flowchart illustrates the injection quantity allocation process. The "S" preceding the symbol in the diagram indicates "step". During the implementation of segmented injection, the ECM20 repeats this process for each fuel injection quantity calculation cycle. Figure 2 The processing.

[0020] When it begins Figure 2During processing, the ECM20 first obtains the required injection quantity Q in the S100. The values ​​of the air-fuel ratio feedback correction value (LMB) and the total injection quantity (QT) are calculated in processes different from this one.

[0021] Next, ECM20 determines the compression stroke segmentation factor SC in S102. The compression stroke segmentation factor SC represents the ratio of fuel injected during the compression stroke to fuel burned in combustion chamber 11. ECM20 calculates the value of the compression stroke segmentation factor SC based on the operating conditions of the internal combustion engine 10, such as engine speed NE, engine load rate KL, and engine coolant temperature THW.

[0022] Subsequently, in step S104, the ECM20 calculates the weighting coefficient W. The weighting coefficient W represents the allocation rate of the air-fuel ratio feedback correction value LMB to the compression stroke injection quantity QC. The weighting coefficient W is set to a value between 0 and 1. In this embodiment, the ECM20 calculates the value of the weighting coefficient W based on the start-up coolant temperature THW0 and the cumulative intake air volume IGA. The start-up coolant temperature THW0 represents the engine coolant temperature THW when the internal combustion engine 10 starts. The start-up coolant temperature THW0 corresponds to the wall temperature of the combustion chamber 11 when the internal combustion engine 10 starts. On the other hand, the cumulative intake air volume IGA represents the cumulative value of the intake air volume GA after the internal combustion engine 10 starts. This cumulative intake air volume IGA corresponds to the cumulative value of the heat received by the wall of the combustion chamber 11 after the internal combustion engine 10 starts, so the amount of increase in the cylinder temperature after the internal combustion engine 10 starts can be estimated based on the cumulative intake air volume IGA. Therefore, the current cylinder temperature can be estimated based on the start-up coolant temperature THW0 and the cumulative intake air volume IGA. ECM20 determines the value of the weighting factor W based on the in-cylinder temperature estimated from the start-up water temperature THW0 and the cumulative intake air volume IGA.

[0023] Next, ECM20 calculates in S106 the value that satisfies the relationship of equation (1) as the value of the injection quantity QC during the compression stroke. The first term on the right side of equation (1) represents the required injection quantity Q. The value obtained by multiplying by the compression stroke segmentation factor SC, the second term on the right side of equation (1) represents the value obtained by multiplying the air-fuel ratio feedback correction value LMB by the weighting factor W. That is, ECM20 will require an injection quantity Q The amount of the ratio corresponding to the value of the compression stroke segmentation coefficient SC and the amount of the ratio corresponding to the value of the air-fuel ratio feedback correction value LMB are allocated to the compression stroke injection quantity QC.

[0024] Formula (1): QC=SC·Q +W·LMB

[0025] Furthermore, in the following S108, ECM20 calculates the intake stroke injection quantity QI by subtracting the compression stroke injection quantity QC from the total injection quantity QT. As mentioned above, the total injection quantity QT is calculated by subtracting the air-fuel ratio feedback correction value LMB from the required injection quantity Q. The values ​​obtained by adding them together. Therefore, the intake stroke injection quantity QI becomes the value that satisfies the relationship of equation (2). The first term on the right side of equation (2) is the value obtained by subtracting the compression stroke segmentation coefficient SC from "1" (=1-SC) multiplied by the required injection quantity Q. The value obtained is the second term on the right side of equation (2), which is the value obtained by subtracting the weighting coefficient W from "1" (=1-W) and multiplying it by the air-fuel ratio feedback correction value LMB. After calculating the intake stroke injection quantity QI, ECM20 ends the current calculation cycle. Figure 2 The processing.

[0026] Equation (2): QI = (1-SC)·Q +(1-W)·LMB

[0027] Figure 3 Shown in Figure 2 In S104, the ECM20 calculates the weighting coefficient W in relation to the in-cylinder temperature estimated based on the start-up water temperature THW0 and the cumulative intake air volume IGA. The ECM20 sets the weighting coefficient W to "1" when the in-cylinder temperature is below the first temperature TA, and sets it to "0" when the in-cylinder temperature exceeds the second temperature TB, which is higher than the first temperature TA. Furthermore, when the in-cylinder temperature is above the first temperature TA and below the second temperature TB, the ECM20 sets the weighting coefficient W to a value that decreases from "1" (when the in-cylinder temperature is at the first temperature TA) to "0" (when the in-cylinder temperature is at the second temperature TB) as the in-cylinder temperature increases.

[0028] In this embodiment, the weighting coefficient W corresponds to the allocation rate of the air-fuel ratio feedback correction value LMB to the compression stroke injection quantity QC. The ECM 20 sets the value of the weighting coefficient W such that the allocation rate of the air-fuel ratio feedback correction value LMB to the compression stroke injection quantity QC is larger when the in-cylinder temperature is low compared to when the in-cylinder temperature is high. In other words, the ECM 20 sets the value of the weighting coefficient W such that, when the internal combustion engine 10 is operating in a cold state, the allocation rate of the air-fuel ratio feedback correction value LMB to the compression stroke injection quantity QC is increased compared to when it is operating in a hot state.

[0029] <The Role of the Implementation Method>

[0030] In the fuel injection control device of this embodiment, the ECM20 performs air-fuel ratio feedback correction on the fuel injection quantity based on the deviation between the detected value of the air-fuel ratio of the mixture burned in the combustion chamber 11 and the target value. The ECM20 uses this air-fuel ratio feedback correction to suppress deviations in fuel injection quantity caused by individual differences in the fuel injection characteristics of the in-cylinder injection valve 16, annual variations, etc. During split injection, the air-fuel ratio feedback correction value LMB needs to be allocated to either or both of the intake stroke injection quantity QI and the compression stroke injection quantity QC.

[0031] In the following description, the proportion of fuel that does not contribute to combustion in the fuel injected by the in-cylinder injection valve 16 is referred to as the non-contributing fuel proportion. During cold-state operation of the internal combustion engine 10, when the in-cylinder temperature is low, fuel is difficult to vaporize, thus the non-contributing fuel proportion is larger compared to hot-state operation. When the non-contributing fuel proportion is large, the proportion of actually burned fuel in the fuel corresponding to the air-fuel ratio feedback correction amount is smaller. Therefore, during cold-state operation, there is a need to compensate for the required injection quantity Q. The required air-fuel ratio feedback correction value (LMB) for the deviation from the actual amount of fuel burned tends to be larger than that required during hot operation. As the LMB increases, the amount of uncontributed fuel further increases. Consequently, this can potentially lead to increased fuel consumption, worsened emissions, and deteriorated driving performance due to combustion degradation in the internal combustion engine 10.

[0032] In contrast, in this embodiment, the ECM 20 adjusts the allocation ratio of the air-fuel ratio feedback correction value LMB for the intake stroke injection quantity QI and the compression stroke injection quantity QC according to the in-cylinder temperature. Specifically, the ECM 20 variably sets the allocation ratio based on the in-cylinder temperature of the internal combustion engine 10, such that the allocation ratio of the air-fuel ratio feedback correction value LMB to the compression stroke injection quantity QC is larger when the in-cylinder temperature is low compared to when the in-cylinder temperature is high. Therefore, the allocation ratio of the air-fuel ratio feedback correction value LMB to the compression stroke injection quantity QC is larger when the internal combustion engine 10 is cold than when it is hot. Furthermore, the allocation ratio of the air-fuel ratio feedback correction value LMB to the intake stroke injection quantity QI is smaller when the internal combustion engine 10 is cold than when it is hot.

[0033] During the compression stroke, the cylinder temperature rises due to the compression of the intake air. Therefore, during cold operation, the proportion of uncontributed fuel injected during the compression stroke is smaller than that injected during the intake stroke. Thus, in split injection during cold operation with low cylinder temperatures, the increase in uncontributed fuel can be suppressed by allocating an air-fuel ratio feedback correction value (LMB) to the compression stroke injection, which has a smaller proportion of uncontributed fuel compared to the intake stroke injection.

[0034] Furthermore, compared to intake stroke injection, compression stroke injection faces more constraints regarding the start / end timing of injection, making it difficult to address fluctuations in the injection period through air-fuel ratio feedback correction. Additionally, during hot operation, the time until combustion begins is longer, and fuel atomization progresses due to in-cylinder airflow; therefore, even in intake stroke injection, the proportion of non-contributing fuel is minimized. Consequently, during hot operation, the ECM20 allocates the air-fuel ratio feedback correction value LMB to intake stroke injection, which is easier to handle fluctuations in the injection period compared to compression stroke injection.

[0035] It should be noted that, in this embodiment, when the in-cylinder temperature is lower than the first temperature TA, the ECM20 sets the weighting coefficient W to "1", thereby allocating the air-fuel ratio feedback correction value LMB entirely to the compression stroke injection quantity QC. Conversely, when the in-cylinder temperature exceeds the second temperature TB, the ECM20 sets the weighting coefficient W to "0", thereby allocating the air-fuel ratio feedback correction value LMB entirely to the intake stroke injection quantity QI. Furthermore, when the in-cylinder temperature is within the range of the first temperature TA to the second temperature TB, the ECM20 sets the value of the weighting coefficient W to a value that decreases from "1" to "0" as the in-cylinder temperature increases. Therefore, the allocation rate of the air-fuel ratio feedback correction value LMB to the compression stroke injection quantity QC decreases from "1" to "0" as the in-cylinder temperature increases from the first temperature TA to the second temperature TB.

[0036] <Effects of the Implementation Method>

[0037] The fuel injection control device of the internal combustion engine 10 in this embodiment has the following effects.

[0038] (1) When the ECM20 performs split injection of intake stroke injection and compression stroke injection, it increases the allocation rate of the air-fuel ratio feedback correction value LMB to the compression stroke injection quantity QC when the internal combustion engine 10 is running cold compared to when it is running hot. As a result, it can suppress the increase of the air-fuel ratio feedback correction value LMB when running cold. That is, the fuel injection control device can suppress the increase in the amount of fuel that does not contribute to combustion when the internal combustion engine 10 performs split injection of intake stroke injection and compression stroke injection when running cold. As a result, it can suppress the increase in fuel consumption of the internal combustion engine 10 caused by the increase in non-contributing fuel, the deterioration of emissions, and the deterioration of driving performance caused by the deterioration of combustion.

[0039] (2) The ECM20 variably sets the allocation ratio of the air-fuel ratio feedback correction value LMB to the intake stroke injection quantity QI and the compression stroke injection quantity QC during split injection based on the in-cylinder temperature of the internal combustion engine 10. Specifically, the ECM20 variably sets the allocation ratio of the air-fuel ratio feedback correction value LMB to the compression stroke injection quantity QC in a manner that the allocation ratio of the air-fuel ratio feedback correction value LMB to the compression stroke injection quantity QC is larger when the in-cylinder temperature is low compared to when the in-cylinder temperature is high. Therefore, the allocation ratio of the air-fuel ratio feedback correction value LMB to the intake stroke injection quantity QI and the compression stroke injection quantity QC can be appropriately adjusted according to the rise in in-cylinder temperature.

[0040] (3) The ECM20 estimates the in-cylinder temperature based on the water temperature THW0 at the start of the internal combustion engine 10 and the cumulative intake air volume IGA after the internal combustion engine 10 starts. Therefore, even without directly detecting the in-cylinder temperature, the air-fuel ratio feedback correction value LMB can be appropriately adjusted according to the in-cylinder temperature to allocate the intake stroke injection quantity QI and the compression stroke injection quantity QC.

[0041] (Other implementation methods)

[0042] The above-described embodiments can be implemented by modification as follows. The above-described embodiments and the following modifications can be combined with each other within the scope of technical inconsistency.

[0043] • The cylinder temperature can also be estimated in a way different from the above-described embodiments. For example, the cylinder temperature can be estimated based on the engine coolant temperature (THW), the ambient temperature, and the elapsed time after startup. Alternatively, the cylinder temperature can be directly detected using a temperature sensor that detects the cylinder wall temperature.

[0044] In the above-described embodiments, when the in-cylinder temperature is lower than the first temperature TA, the allocation rate of the air-fuel ratio feedback correction value LMB to the intake stroke injection quantity QI is set to "0". Alternatively, the allocation rate of the air-fuel ratio feedback correction value LMB to the intake stroke injection quantity QI can be set to a certain value or higher, regardless of the in-cylinder temperature. Furthermore, when the in-cylinder temperature exceeds the second temperature TB, the allocation rate of the air-fuel ratio feedback correction value LMB to the compression stroke injection quantity QC is set to "0". Alternatively, the allocation rate of the air-fuel ratio feedback correction value LMB to the compression stroke injection quantity QC can be set to a certain value or higher, regardless of the in-cylinder temperature.

[0045] Regarding the allocation method of the air-fuel ratio feedback correction value LMB in the above embodiments for the intake stroke injection quantity QI and the compression stroke injection quantity QC, it can be appropriately changed as long as the allocation rate for the compression stroke injection quantity QC is larger when operating in cold conditions compared to when operating in hot conditions.

[0046] Regarding the above-described embodiments, the ECM20 includes a CPU (Central Processing Unit), RAM (Random Access Memory), and ROM (Read Only Memory). The ECM20 performs software processing. However, this is merely an example. For instance, the ECM20 may also include dedicated hardware circuitry for processing at least a portion of the software processing performed in the above-described embodiments. The dedicated hardware circuitry is, for example, an Application Specific Integrated Circuit (ASIC). That is, the ECM20 can be any of the following structures (a) to (c): (a) The ECM20 includes a processing device that performs all processing according to a program and a program storage device such as a ROM that stores the program. That is, the ECM20 includes a software execution device. (b) The ECM20 includes a processing device that performs a portion of the processing according to a program and a program storage device. Furthermore, the ECM20 includes dedicated hardware circuitry for performing the remaining processing. (c) The ECM20 includes dedicated hardware circuitry for performing all processing. Here, there may be multiple software execution devices and / or dedicated hardware circuitry. That is, the above-described processing can be executed by at least one of a processing circuitry having a software execution device and dedicated hardware circuitry. The processing circuitry may include multiple software execution devices and dedicated hardware circuitry. The program storage device, i.e., computer-readable medium, includes all available media, i.e., storage devices, that can be accessed by a general-purpose or special-purpose computer.

Claims

1. A fuel injection control device for an internal combustion engine, wherein the internal combustion mechanism performs segmented injection, which involves injecting fuel into the combustion chamber by dividing the injection into the intake stroke and the compression stroke, wherein... The fuel injection control device of the internal combustion engine includes a processing circuit, which is configured to, During the segmented injection, the correction value for the fuel injection amount used to compensate for the deviation between the target value and the detected value of the air-fuel ratio, namely the air-fuel ratio feedback correction value, is allocated and applied to the fuel injection amount of the intake stroke injection and the fuel injection amount of the compression stroke injection. Furthermore, when the internal combustion engine is operating in a cold state, compared to when it is operating in a hot state, the distribution rate of the air-fuel ratio feedback correction value to the fuel injection quantity during the compression stroke is increased.

2. The fuel injection control device for an internal combustion engine according to claim 1, wherein, The processing circuit is configured to set the allocation rate of the air-fuel ratio feedback correction value to the fuel injection quantity of the compression stroke injection and the allocation rate of the air-fuel ratio feedback correction value to the fuel injection quantity of the intake stroke injection based on the in-cylinder temperature, so that when the in-cylinder temperature is low, the allocation rate of the air-fuel ratio feedback correction value to the fuel injection quantity of the compression stroke injection is larger than when the in-cylinder temperature is high.

3. The fuel injection control device for an internal combustion engine according to claim 2, wherein, The processing circuit is configured to estimate the cylinder temperature based on the water temperature at startup of the internal combustion engine and the cumulative amount of air drawn in after startup.

4. The fuel injection control device for an internal combustion engine according to claim 1, wherein, The processing circuit is configured to, as the air-fuel ratio feedback correction value, represent the distribution rate of the compression stroke injection. Set to 1 when the cylinder temperature is lower than the first temperature. When the cylinder temperature exceeds a second temperature that is higher than the first temperature, the setting is 0. When the cylinder temperature is above the first temperature and below the second temperature, a value is set that decreases from the value 1 when the cylinder temperature is the first temperature to the value 0 when the cylinder temperature is the second temperature, depending on the increase in the cylinder temperature.

5. A fuel injection control method for an internal combustion engine, wherein, This includes the steps of determining the fuel injection quantity during the intake stroke (i.e., the intake stroke injection quantity) and the fuel injection quantity during the compression stroke immediately following the intake stroke (i.e., the compression stroke injection quantity) according to the following formula: QC=SC·Q +W·LMB QI=(1-SC)·Q +(1-W)·LMB Here, QC is the compression stroke injection quantity, QI is the intake stroke injection quantity, and the sum of QC and QI is the total amount of fuel that should be supplied to the cylinder for one combustion event. SC is the reference amount of fuel that should be supplied to the cylinder for the aforementioned combustion event, i.e., the required injection amount. SC is a compression stroke division factor greater than or equal to 0 and less than 1. LMB is an air-fuel ratio feedback correction value used to correct the reference amount based on the detected air-fuel ratio value obtained from the air-fuel ratio sensor. W is a weighting factor greater than or equal to 0 and less than 1. When the temperature inside the cylinder, i.e., the cylinder temperature, is within a range lower than the first temperature, the weighting coefficient is 1. The weighting coefficient is 0 when the cylinder temperature is within a range that is higher than a second temperature, which is higher than the first temperature. When the in-cylinder temperature is in the range of above the first temperature and below the second temperature, the weighting coefficient decreases from 1 to 0 as the in-cylinder temperature increases. The fuel injection control method further includes the following steps: During the intake stroke, fuel of the determined intake stroke injection amount is injected into the cylinder; and During the compression stroke, the determined amount of fuel to be injected into the cylinder is delivered.

6. A fuel injection control device for an internal combustion engine, the internal combustion mechanism being configured to perform segmented fuel injection into the cylinder in such a manner that the sum of the fuel injection amount during the intake stroke (i.e., the intake stroke injection amount) and the fuel injection amount during the compression stroke immediately following the intake stroke (i.e., the compression stroke injection amount) is consistent with the total amount of fuel to be supplied to the cylinder for a combustion event, wherein... The fuel injection control device includes a processing circuit configured to perform the following steps: During the split injection, an air-fuel ratio feedback correction value is obtained. This air-fuel ratio feedback correction value is a correction value for the fuel injection quantity used to compensate for the deviation between the target value and the detected value of the air-fuel ratio. The allocation rate is set such that, when the internal combustion engine is operating in a cold state, the allocation rate of the air-fuel ratio feedback correction value to the compression stroke injection quantity is larger compared to when it is operating in a hot state. and The air-fuel ratio feedback correction value is allocated and applied to the intake stroke injection quantity and the compression stroke injection quantity based on the allocation rate of the air-fuel ratio feedback correction value to the compression stroke injection quantity.

7. The fuel injection control device for an internal combustion engine according to claim 6, wherein, The lower the temperature inside the cylinder, the greater the distribution rate of the air-fuel ratio feedback correction value to the compression stroke injection quantity.

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