JP6969492B2 - Fuel injection control device for internal combustion engine - Google Patents

Description

The present invention relates to a fuel injection control device for an internal combustion engine applied to an internal combustion engine provided with a port injection valve for injecting fuel into an intake passage.

For example, in Patent Document 1 below, the amount of fuel required based on the amount of intake air is divided into an intake stroke injection that injects fuel into the intake stroke and an exhaust stroke injection that injects fuel into the exhaust stroke. A fuel injection control device that executes a multi-injection process that operates a port injection valve is described.

Japanese Unexamined Patent Publication No. 5-256172

In the multi-injection process, the inventor makes various corrections to the fuel injection amount determined from the amount of fresh air filled in the combustion chamber, and at least one of the divided injection amounts is the minimum injection of the port injection valve. It has been found that the amount may be less than the amount, and in that case, the controllability of the injection amount may be lowered and the exhaust characteristics may be deteriorated.

Hereinafter, means for solving the above problems and their actions and effects will be described.
1. 1. The fuel injection control device of an internal combustion engine is applied to an internal combustion engine provided with a port injection valve for injecting fuel into an intake passage, and the air-fuel ratio is set to the target air-fuel ratio based on the amount of fresh air filled in the cylinder of the internal combustion engine. The required injection amount calculation process for calculating the required injection amount for control and the port injection valve to inject the fuel of the required injection amount are operated to inject fuel in synchronization with the valve opening period of the intake valve. Even if the amount of fresh air to be filled is the same, the multi-injection process that executes the intake synchronous injection to be performed and the intake asynchronous injection to inject fuel at the timing on the advance side of the intake synchronous injection is predetermined. When the condition of is satisfied, the port injection valve allows an asynchronous injection amount which is an injection amount of the intake asynchronous injection determined from the required injection amount reduced by the reduction process and the reduction process of reducing the required injection amount. If it is less than the minimum injection amount, the asynchronous injection amount is increased so as to be equal to or more than the minimum injection amount, and the synchronous injection amount, which is the injection amount of the intake synchronous injection, is decreased.

In the above configuration, when the asynchronous injection amount is less than the minimum injection amount, the asynchronous injection amount is increased so as to be equal to or more than the minimum injection amount, and the synchronous injection amount is decreased. As a result, it is possible to prevent the sum of the asynchronous injection amount and the synchronous injection amount from deviating from the required injection amount while preventing the asynchronous injection amount from becoming less than the minimum injection amount. Therefore, it is possible to suppress a decrease in controllability of the injection amount.

2. 2. In the fuel injection control device according to 1 above, in the two-way correction process, the difference between the asynchronous injection amount and the minimum injection amount before correction is used as the increase correction amount of the asynchronous injection amount and the decrease correction amount of the synchronous injection amount. A single injection process for injecting the fuel of the required injection amount by the intake asynchronous injection by operating the port injection valve and a selection process for selecting one of the multi-injection process are executed. The selection process includes a process of selecting the single injection process when the synchronous injection amount reduced by the reduction correction amount is less than the minimum injection amount.

By correcting the difference between the asynchronous injection amount and the minimum injection amount as the reduction correction amount of the synchronous injection amount, if the synchronous injection amount is less than the minimum injection amount, the asynchronous injection amount and the asynchronous injection amount while executing the multi-injection process. Both synchronous injection amounts cannot be greater than or equal to the minimum injection amount. Therefore, in the above configuration, by executing the single injection process in such a case, it is possible to sufficiently suppress the situation where the fuel injection amount less than the minimum injection amount is injected into the port injection valve.

3. 3. In the fuel injection control device for the internal combustion engine according to 1 or 2, the predetermined condition includes a condition that the fresh air amount is reduced, and the weight reduction process is performed when the fresh air amount is reduced. A transient correction process for reducing the required injection amount by reducing the asynchronous injection amount is included.

When the amount of fresh air decreases, the amount of fuel adhering to the intake passage decreases transiently, and this decrease is added and flows into the combustion chamber. Therefore, the required injection calculated based on the amount of fresh air. The amount may be excessive in controlling the air-fuel ratio to the target air-fuel ratio. Therefore, in the above configuration, when the fresh air amount decreases, the required injection amount is suppressed from becoming excessive by reducing the asynchronous injection amount. However, in that case, the asynchronous injection amount may be less than the minimum injection amount. Therefore, the utility value of both correction processing is particularly large.

4. In the fuel injection control device for an internal combustion engine according to any one of the above 1 to 3, the single injection process of operating the port injection valve to inject the fuel of the required injection amount by the intake asynchronous injection and the multi A selection process for selecting one of the injection processes is executed, and the predetermined condition is a condition that the single injection process is selected by the selection process and the multi-injection process is selected. Is included, and when the selection process switches from the state in which the single injection process is selected to the state in which the multi-injection process is selected, the weight reduction process reduces the asynchronous injection amount to obtain the required injection amount. Includes transient correction processing to reduce the weight.

Since the intake synchronous injection has less fuel adhering to the intake passage than the intake asynchronous injection, the amount of fuel adhering to the intake passage when the multi-injection process is performed is compared with the case where the single injection process is performed. Less is. Therefore, when the single injection process is switched to the multi-injection process, the amount of fuel adhering to the intake passage decreases transiently, and this decrease flows into the combustion chamber, so it is calculated based on the amount of fresh air. The required injection amount may be excessive in controlling the air-fuel ratio to the target air-fuel ratio. Therefore, in the above configuration, when switching to the multi-injection process, the required injection amount is suppressed from becoming excessive by reducing the asynchronous injection amount. However, in that case, the asynchronous injection amount may be less than the minimum injection amount. Therefore, the utility value of both correction processing is particularly large.

5. In the fuel injection control device for an internal combustion engine according to any one of the above 1 to 4, a division process for dividing the required injection amount into the asynchronous injection amount and the synchronous injection amount is executed, and the reduction process is performed. This is a process of reducing the amount only for the asynchronous injection amount.

When the synchronous injection amount is changed as compared with the case where the asynchronous injection amount is changed, the exhaust characteristics may fluctuate significantly. Therefore, in the above configuration, by limiting the weight reduction target of the weight reduction treatment to the asynchronous injection amount, it is possible to suppress the deterioration of the exhaust characteristics due to the weight reduction treatment.

The figure which shows the control device and the internal combustion engine which concerns on one Embodiment. The block diagram which shows the process executed by the control device which concerns on the same embodiment. (A) and (b) are time charts showing an injection pattern according to the same embodiment. The flow chart which shows the procedure of the injection valve operation processing which concerns on the same embodiment. (A) and (b) are diagrams showing the significance of setting the arrival end time according to the same embodiment. (A) to (c) are time charts showing the effects of the same embodiment. (A) to (c) are time charts showing the effects of the same embodiment.

Hereinafter, an embodiment of the fuel injection control device for an internal combustion engine will be described with reference to the drawings.
A throttle valve 14 is provided in the intake passage 12 of the internal combustion engine 10 shown in FIG. 1, and a port injection valve 16 is provided downstream of the throttle valve 14. The air sucked into the intake passage 12 and the fuel injected from the port injection valve 16 flow into the combustion chamber 24 partitioned by the cylinder 20 and the piston 22 as the intake valve 18 opens. In the combustion chamber 24, the air-fuel mixture is subjected to combustion by the spark discharge of the ignition device 26, and the combustion energy generated at that time is converted into the rotational energy of the crank shaft 28 via the piston 22. .. The air-fuel mixture used for combustion is discharged to the exhaust passage 32 as exhaust gas when the exhaust valve 30 is opened. A catalyst 34 is provided in the exhaust passage 32.

The rotational power of the crank shaft 28 is transmitted to the intake side cam shaft 40 and the exhaust side cam shaft 42 via the timing chain 38. In the present embodiment, the power of the timing chain 38 is transmitted to the intake side camshaft 40 via the intake side valve timing adjusting device 44. The intake side valve timing adjusting device 44 is an actuator that adjusts the valve opening timing of the intake valve 18 by adjusting the rotational phase difference between the crank shaft 28 and the intake side cam shaft 40.

The control device 50 targets the internal combustion engine 10 as a control target, and in order to control the control amount (torque, exhaust component ratio, etc.), the throttle valve 14, the port injection valve 16, the ignition device 26, and the intake side valve timing adjustment. The operation unit of the internal combustion engine 10 such as the device 44 is operated. At this time, the control device 50 uses the output signal Scr of the crank angle sensor 60, the intake air amount Ga detected by the air flow meter 62, the air-fuel ratio Af detected by the air-fuel ratio sensor 64, and the output of the intake side cam angle sensor 66. The signal Sca and the temperature (water temperature THW) of the cooling water of the internal combustion engine 10 detected by the water temperature sensor 68 are referred to. Note that FIG. 1 shows an operation signal MS1 for operating the throttle valve 14, an operation signal MS2 for operating the port injection valve 16, an operation signal MS3 for operating the ignition device 26, and an intake side valve timing adjusting device. The operation signal MS4 for operating 44 is described.

The control device 50 includes a CPU 52, a ROM 54, and a power supply circuit 56 that supplies electric power to each location in the control device 50, and the CPU 52 executes a program stored in the ROM 54 to control the control amount. Run.

FIG. 2 shows a part of the processing executed by the control device 50. The process shown in FIG. 2 is realized by the CPU 52 executing the program stored in the ROM 54.
The intake phase difference calculation process M10 is based on the output signal Scr of the crank angle sensor 60 and the output signal Sca of the intake side cam angle sensor 66, and is the phase difference of the rotation angle of the intake side cam shaft 40 with respect to the rotation angle of the crank shaft 28. This is a process for calculating a certain intake phase difference DIN. The target intake phase difference calculation process M12 is a process for variably setting the target intake phase difference DIN * based on the operating point of the internal combustion engine 10. In this embodiment, the operating point is defined by the rotation speed NE and the filling efficiency η. Here, the CPU 52 calculates the rotation speed NE based on the output signal Scr of the crank angle sensor 60, and calculates the filling efficiency η based on the rotation speed NE and the intake air amount Ga. The filling efficiency η is a parameter that determines the amount of fresh air filled in the combustion chamber 24.

The intake phase difference control process M14 is a process of outputting an operation signal MS4 in order to operate the intake side valve timing adjusting device 44 in order to control the intake phase difference DIN * to the target intake phase difference DIN *.

The base injection amount calculation process M20 is a process of calculating the base injection amount Qb, which is the base value of the fuel amount for setting the air-fuel ratio of the air-fuel mixture in the combustion chamber 24 as the target air-fuel ratio, based on the filling efficiency η. Specifically, in the base injection amount calculation process M20, for example, when the filling efficiency η is expressed as a percentage, the filling efficiency η is set to the fuel amount QTH per 1% of the filling efficiency η for setting the air-fuel ratio as the target air-fuel ratio. The process may be such that the base injection amount Qb is calculated by multiplying. The base injection amount Qb is a fuel amount calculated to control the air-fuel ratio to the target air-fuel ratio based on the amount of fresh air filled in the combustion chamber 24. Incidentally, the target air-fuel ratio may be, for example, the theoretical air-fuel ratio.

The feedback processing M22 calculates a feedback correction coefficient KAF obtained by adding "1" to the correction ratio δ of the base injection amount Qb as the feedback operation amount, which is the operation amount for feedback control of the air-fuel ratio Af to the target value Af *. It is a process to output. Specifically, the feedback processing M22 holds and outputs the output values of the proportional element and the differential element that input the difference between the air-fuel ratio Af and the target value Af *, and the integrated value of the values corresponding to the difference. The sum with the output value of is defined as the correction ratio δ.

The low temperature correction process M24 is a process of calculating the low temperature increase coefficient Kw to a value larger than “1” in order to increase the base injection amount Qb when the water temperature THW is less than the specified temperature Tth (for example, 70 ° C.). Specifically, the low temperature increase coefficient Kw is calculated to be a larger value when the water temperature THW is low than when it is high. When the water temperature THW is equal to or higher than the specified temperature Tth, the low temperature increase coefficient Kw is set to "1", and the correction amount of the base injection amount Qb by the low temperature increase coefficient Kw is set to zero.

The transient correction process M26 is a transient correction as an operation amount of feedforward control that suppresses an excess or deficiency of the amount of fuel flowing into the combustion chamber 24 when the amount of fuel adhering to the intake passage 12 changes. This is a process for calculating the quantity ΔQ. In the transient correction process M26, for example, when the filling efficiency η decreases, the amount of fuel adhering to the intake passage 12 decreases transiently, and this decrease is added to the fuel flowing into the combustion chamber 24. Since the amount is excessive with respect to the base injection amount Qb, a process of calculating the transient correction amount ΔQ to a negative value is included. Further, for example, in the transient correction process M26, when the filling efficiency η increases, the amount of fuel adhering to the intake passage 12 increases transiently, and as a result, the amount of fuel adhering to the intake passage 12 increases in the combustion chamber 24. Since the amount of fuel flowing in is insufficient with respect to the base injection amount Qb, a process of calculating the transient correction amount ΔQ to a positive value is included. Specifically, the transient correction process M26 calculates the transient correction amount ΔQ based on the filling efficiency η, the water temperature THW, the rotation speed NE, the intake phase difference DIN, and whether it is the multi-injection process or the single-injection process described later. It is a process. The transient correction amount ΔQ is zero at steady state.

Incidentally, FIG. 2 shows a curve f2 showing the relationship between the filling efficiency η and the adhesion amount in the case of the multi-injection process, a curve f1 showing the relationship between the filling efficiency η and the adhesion amount in the case of the single injection process, and a multi. It is schematically shown that the change amount of the adhesion amount when the filling efficiency η changes from “η1” to “η2” in the case of the injection process is “ΔQ”. However, in the present embodiment, for example, when the filling efficiency is reduced from "η1" to "η2" in one combustion cycle, the transient correction amount ΔQ is schematically shown in FIG. 2 only in the next combustion cycle. This does not mean that the transient correction amount ΔQ is set to a value different from zero over a predetermined period.

The injection valve operation process M30 outputs an operation signal MS2 to the port injection valve 16 in order to operate the port injection valve 16 based on the base injection amount Qb, the feedback correction coefficient KAF, the low temperature increase coefficient Kw, and the transient correction amount ΔQ. Is. More specifically, it is a process of injecting the required injection amount Qd, which is the amount of fuel required to be supplied to one cylinder from the port injection valve 16 in one combustion cycle, from the port injection valve 16. Here, the required injection amount Qd is "KAF · Kw · Qb + ΔQ".

In the present embodiment, the fuel injection process has two types of processes, the process exemplified in FIG. 3 (a) and the process exemplified in FIG. 3 (b).
FIG. 3A shows two types of intake synchronous injection, in which fuel is injected in synchronization with the valve opening period of the intake valve 18, and intake asynchronous injection, in which fuel is injected at a timing on the advance side of the intake synchronous injection. It is a multi-injection process that executes fuel injection. Specifically, in the intake synchronous injection, the period during which the fuel injected from the port injection valve 16 reaches the position before the opening of the intake valve 18 (the downstream end of the intake port, in other words, the inlet portion to the combustion chamber 24) is The fuel is injected so as to be within the valve opening period of the intake valve 18. Here, the start point of the "reaching period" is the timing at which the fuel injected at the earliest timing among the fuels injected from the port injection valve 16 reaches the position before valve opening, and the end point is the port injection. This is the timing at which the fuel injected at the latest timing among the fuels injected from the valve 16 reaches the position before the valve is opened. On the other hand, in the intake asynchronous injection, the fuel injected from the port injection valve 16 is injected so as to reach the intake valve 18 before the intake valve 18 opens. In other words, the intake asynchronous injection is an injection in which the fuel injected from the port injection valve 16 stays in the intake passage 12 until the intake valve 18 is opened, and then flows into the combustion chamber 24 after the valve is opened. be. In the intake asynchronous injection in the present embodiment, the fuel is injected so that the period during which the fuel injected from the port injection valve 16 reaches the position before the opening of the intake valve 18 falls within the valve closing period of the intake valve 18. It shall be.

FIG. 3B is a single injection process that executes only intake asynchronous injection.
In the present embodiment, the multi-injection process is performed with the aim of reducing the number of particulate matter (PM) (PN) in the exhaust gas. That is, when the water temperature THW is low to some extent, the PN tends to increase when the single injection process is executed in the region where the filling efficiency η is large to some extent. It is considered that this is because when the filling efficiency η is large, the required injection amount Qd becomes a larger value than when it is small, and as a result, the amount of fuel adhering to the intake passage 12 increases. Specifically, when the amount of fuel adhering to the intake passage 12 increases to some extent, a part of the adhering fuel flows into the combustion chamber 24 as droplets due to the shearing of the adhering fuel. It is inferred that. Therefore, in the present embodiment, in the region where the filling efficiency η is large to some extent, the amount of fuel adhering to the intake passage 12 is small for the large required injection amount Qd by injecting a part of the required injection amount Qd by the intake synchronous injection. As a result, PN will be reduced.

The transient correction process M26 in FIG. 2 sets the transient correction amount ΔQ to a value other than zero even when switching between the multi-injection process and the single-injection process. That is, the amount of fuel adhering to the intake passage 12 is larger when the single injection process is performed than when the multi-injection process is performed. Therefore, for example, when switching from the single injection process to the multi-injection process, the amount of fuel adhering to the intake passage 12 is transiently reduced, and this reduced amount is added and flows into the combustion chamber 24. Therefore, by setting the transient correction amount ΔQ to a value smaller than zero, it is possible to prevent the amount of fuel flowing into the combustion chamber 24 from becoming excessive.

FIG. 4 shows a procedure for processing the injection valve operation processing M30. The process shown in FIG. 4 is realized by the CPU 52 repeatedly executing the program stored in the ROM 54, for example, at a predetermined cycle. In the following, the step number of each process is represented by a number prefixed with "S".

In the series of processes shown in FIG. 4, the CPU 52 first determines whether or not there is a request to execute the multi-injection process (S10). Here, the CPU 52 determines that there is a request to execute the multi-injection process when the logical product of the following conditions (a), (b), and (c) is true.

Condition (a): It is a condition that the filling efficiency η is equal to or higher than a predetermined value. This condition is a condition that the amount of fuel adhering to the intake passage 12 may become excessively large and the PN may become remarkable if the single injection process is performed.

Condition (a): It is a condition that the rotation speed NE is equal to or less than the predetermined speed NEth. This condition is a condition that the time interval between the end timing of the intake asynchronous injection and the start timing of the intake synchronous injection can be secured at a predetermined time or more determined by the structure of the port injection valve 16. Further, this condition is a condition for suppressing an excessive heat generation amount due to an increase in the calculation load of the control device 50 because the calculation load of the multi-injection process is larger than that of the single injection process.

Condition (c): It is a condition that the water temperature THW is equal to or less than the above-mentioned specified temperature Tth. This condition is a condition that the amount of fuel adhering to the intake passage 12 becomes large and the PN may become remarkable.

Then, when it is determined that there is no request (S10: NO), the CPU 52 calculates the requested injection amount Qd by executing the single injection process (S12).
Next, the CPU 52 calculates the injection start time Isin (S14). Specifically, as shown in FIG. 3B, the CPU 52 advances the timing of the intake valve 18 by a predetermined amount Δ1 with respect to the valve opening timing, which is the latest timing among the fuels injected from the port injection valve 16. Let it be the arrival end time AEns, which is the target value of the timing at which the fuel injected in 1 reaches the position in the valve closing period of the intake valve 18. Next, the CPU 52 is a value obtained by adding the injection period by the port injection valve 16 determined from the required injection amount, the flight time until the fuel injected from the port injection valve 16 reaches the position when the intake valve 18 is closed, and the like. However, the timing of advancing with respect to the arrival end time AEns is defined as the injection start time Isin. Returning to FIG. 4, the CPU 52 outputs the operation signal MS2 to the port injection valve 16 to inject the fuel having the required injection amount Qd at the injection start time Isin, and operates the port injection valve 16 (S16).

On the other hand, when it is determined that there is an execution request for the multi-injection process (S10: YES), the CPU 52 calculates the synchronous injection ratio Ks, which is the ratio of the synchronous injection amount Qs to the base injection amount Qb (S18). Here, the CPU 52 calculates the synchronous injection ratio Ks according to the rotation speed NE, the filling efficiency η, the water temperature THW, and the intake phase difference DIN. Specifically, the CPU 52 stores the map data with the rotation speed NE, the filling efficiency η, the water temperature THW, and the intake phase difference DIN as the input variables and the synchronous injection ratio Ks as the output variable in advance in the ROM 54, and the synchronous injection ratio Ks. Is calculated on the map.

The map data is a set of data of discrete values of input variables and values of output variables corresponding to the values of the input variables. In the map operation, for example, if the value of the input variable matches any of the values of the input variable of the map data, the value of the output variable of the corresponding map data is used as the operation result, and if they do not match, the value is included in the map data. The processing may be performed using the value obtained by interpolating the values of a plurality of output variables as the calculation result.

Next, the CPU 52 calculates the asynchronous injection ratio Kns as the ratio of the synchronous injection amount Qs to the required injection amount Qd minus the transient correction amount ΔQ (S20). Specifically, the CPU 52 calculates the asynchronous injection ratio Kns by subtracting “Ks / (KAF · Kw)” from “1”. Next, the CPU 52 substitutes the value obtained by multiplying the base injection amount Qb by the synchronous injection ratio Ks into the synchronous injection amount Qs (S22). Next, the CPU 52 substitutes the sum of the transient injection amount ΔQ and the value obtained by multiplying the value “KAF ・ Kw ・ Qb” obtained by subtracting the transient correction amount ΔQ from the required injection amount Qd by the asynchronous injection ratio Kns into the asynchronous injection amount Qns. (S24).

As a result, the asynchronous injection amount Qns becomes the following value.
Ksn / KAF / Kw / Qb + ΔQ = KAF / Kw / Qb-Ks / Qb + ΔQ
Therefore, the sum of the asynchronous injection amount Qns and the synchronous injection amount Qs is “KAF ・ Kw ・ Qb + ΔQ”, which is equal to the required injection amount Qd. That is, by the processing of S18 to S24, the fuel having the required injection amount Qd is divided into the asynchronous injection amount Qns and the synchronous injection amount Qs. Incidentally, the synchronous injection amount Qs is "Ks · Qb" without being influenced by the values of the feedback correction coefficient KAF, the low temperature increase coefficient Kw, and the transient correction amount ΔQ. This is because the base injection amount Qb is divided into the synchronous injection amount Qs and "(1-Ks) · Qb", and then the corrected value of "(1-Ks) · Qb" is the asynchronous injection amount Qns. Means to be. In this way, the reason why the synchronous injection amount Qs is fixed is that the change in the exhaust component when the synchronous injection amount Qs is changed is more remarkable than the change in the exhaust component when the asynchronous injection amount Qns is changed. ..

Next, the CPU 52 determines whether or not the asynchronous injection amount Qns is equal to or greater than the structural minimum injection amount Qmin of the port injection valve 16 (S26). Here, the minimum injection amount Qmin is set based on the lower limit value at which the accuracy of the injection amount falls within the permissible range when fuel is injected from the port injection valve 16. When the CPU 52 determines that the injection amount is less than the minimum injection amount Qmin (S26: NO), the CPU 52 calculates a difference ΔINS which is a value obtained by subtracting the asynchronous injection amount Qns from the minimum injection amount Qmin (S28). Next, the CPU 52 determines whether or not the value obtained by subtracting the difference ΔINS from the synchronous injection amount Qs is equal to or greater than the minimum injection amount Qmin (S30). Then, when the CPU 52 determines that the injection amount is less than the minimum injection amount Qmin (S30: NO), it is assumed that both the synchronous injection amount Qs and the asynchronous injection amount Qns cannot be simultaneously set to the minimum injection amount Qmin or more, and the processing of S12 is performed. Transition.

On the other hand, when the CPU 52 determines that the minimum injection amount is Qmin or more (S30: YES), the asynchronous injection amount Qns calculated by the processing of S24 is increased and corrected by the difference ΔINS, and is calculated by the processing of S22. The synchronous injection amount Qs is reduced and corrected by the difference ΔINS (S32).

When the processing of S32 is completed or when affirmative determination is made in the processing of S26, the CPU 52 determines the arrival end time shown in FIG. 3A based on the rotation speed NE, the filling efficiency η, the water temperature THW, and the intake phase difference DIN. AEs are calculated (S34). Then, the CPU 52 calculates the injection start time Is of the intake synchronous injection based on the arrival end time, the synchronous injection amount Qs, and the rotation speed NE (S36). Here, the CPU 52 calculates the injection start time Is to a value on the advance angle side when the synchronous injection amount Qs is large and smaller than when it is small. Further, the CPU 52 sets the injection start time Is to a value on the advance angle side more than when the rotation speed NE is large and when the rotation speed NE is small. The arrival end time AEs are adapted so that the fuel injected from the port injection valve 16 does not reach the position when the intake valve 18 is closed before the intake valve 18 is opened. Next, the CPU 52 calculates the injection start time Ins of asynchronous injection based on the injection start time Is (S38). Here, the time interval between the injection end time and the injection start time Is of the intake asynchronous injection is set to be equal to or longer than the predetermined time.

By the above processing, the injection start timing Is of the intake synchronous injection is set independently of the injection start timing Ins of the intake asynchronous injection. This is because the arrival end time of the intake synchronous injection is particularly likely to affect the PN and HC in the exhaust.

FIG. 5A shows the PN when the arrival end time of the intake asynchronous injection and the intake synchronous injection is changed, and FIG. 5B shows the arrival end time of the intake asynchronous injection and the intake synchronous injection. The amount of HC generated at the time of inhalation is shown. Here, the white plot is when the arrival end time of the intake asynchronous injection is fixed and the arrival end time of the intake synchronous injection is changed, and the black plot is the arrival end time of the intake synchronous injection. Is fixed and the arrival end time of the intake asynchronous injection is changed. In addition, in each of the plots marked with a circle, diamond, square, and triangle, the ratio of the asynchronous injection amount Qns to the synchronous injection amount Qs is "8: 2", "7: 3", "6: 4", "5". : 5 ”corresponds to each.

As shown in the white plot of FIG. 5, regardless of the ratio of the asynchronous injection amount Qns and the synchronous injection amount Qs, PN or PN or The amount of HC generated changes significantly. Therefore, in the present embodiment, the arrival end time of the intake synchronous injection is set to an appropriate value that can reduce the amount of PN and HC generated.

Returning to FIG. 4, the CPU 52 injects fuel having a synchronous injection amount Qs at the injection start time Is, and outputs an operation signal MS2 to the port injection valve 16 in order to inject fuel having an asynchronous injection amount Qns at the injection start time Ins. The port injection valve 16 is operated (S16).

When the processing of S16 is completed, the CPU 52 temporarily ends the series of processing shown in FIG.
Here, the operation and effect of this embodiment will be described.

FIG. 6 illustrates the effect of the transient correction amount ΔQ when the filling efficiency η decreases. FIG. 6A shows the asynchronous injection amount Qns and the synchronous injection amount Qs before the reduction of the filling efficiency η by the length of the injection period. FIG. 6B shows the asynchronous injection amount Qns and the synchronous injection amount Qs calculated by the processing of S22 and S24 when the filling efficiency η decreases by the length of the injection period. FIG. 6C shows the asynchronous injection amount Qns and the synchronous injection amount Qs calculated by the processing of S32 when the filling efficiency η decreases by the length of the injection period.

As shown in FIG. 6B, when the filling efficiency η decreases, the asynchronous injection amount Qns becomes very small due to the transient correction amount ΔQ, and becomes less than the minimum injection amount Qmin. In this case, the CPU 52 reduces the synchronous injection amount Qs by the difference ΔINS from the minimum injection amount Qmin, and increases and corrects the asynchronous injection amount Qns to the minimum injection amount Qmin. As a result, both the asynchronous injection amount Qns and the synchronous injection amount Qs can be set to the minimum injection amount Qmin or more.

FIG. 7 illustrates a case of switching from the single injection process to the multi-injection process. FIG. 7A shows the injection amount at the time of single injection processing by the length of the injection period. FIG. 7B shows the asynchronous injection amount Qns and the synchronous injection amount Qs calculated by the processing of S22 and S24 when switching to the multi-injection processing by the length of the injection period. FIG. 7C shows the asynchronous injection amount Qns and the synchronous injection amount Qs calculated by the processing of S32 when switching to the multi-injection processing by the length of the injection period.

As shown in FIG. 7B, when switching to the multi-injection process, the asynchronous injection amount Qns becomes very small due to the transient correction amount ΔQ, and becomes less than the minimum injection amount Qmin. In this case, the CPU 52 reduces the synchronous injection amount Qs by the difference ΔINS from the minimum injection amount Qmin, and increases and corrects the asynchronous injection amount Qns to the minimum injection amount Qmin. As a result, both the asynchronous injection amount Qns and the synchronous injection amount Qs can be set to the minimum injection amount Qmin or more.

In addition, as a situation where the absolute value of the transient correction amount ΔQ becomes large when switching to the multi-injection processing, for example, the rotation speed NE may decrease. That is, when the rotation speed NE is large, the filling efficiency η becomes equal to or higher than the specified value, and the CPU 52 determines that the above condition (a) is not satisfied in the processing of S10, and executes the single injection processing. Here, when the rotation speed NE decreases, the specified value becomes large, so that the CPU 52 switches to the multi-injection process, assuming that the condition of (a) above is satisfied. In this case, the filling efficiency η may be relatively large, and the amount of fuel adhering to the intake passage 12 when the single injection process is being performed and the inside of the intake passage 12 when the multi-injection process is being performed. Since the difference from the amount of fuel adhering to the fuel is large, the absolute value of the transient correction amount ΔQ may become large.

<Correspondence>
The correspondence between the matters in the above embodiment and the matters described in the above-mentioned "means for solving the problem" column is as follows. In the following, the correspondence is shown for each number of the solution means described in the column of "Means for solving the problem". [1] The required injection amount calculation process corresponds to the base injection amount calculation process M20, the feedback process M22, the low temperature correction process M24, and the transient correction process M26. That is, since the required injection amount Qd is "Qb, KAF, Kw + ΔQ", each of the above processes calculates the base injection amount Qb, the feedback correction coefficient KAF, the low temperature increase coefficient Kw, and the transient correction amount ΔQ, respectively. , It can be considered that the required injection amount Qd has been calculated. The multi-injection process corresponds to the process of S16 shifted from the process of S38. The weight loss process corresponds to the process of S24 when the transient correction amount ΔQ is negative. Both correction processing corresponds to the processing of S32. The fuel injection control device corresponds to the control device 50. [2] The selection process corresponds to the processes of S10 and S30. [3] Corresponds to the process illustrated in FIG. [4] Corresponds to the process illustrated in FIG. [5] The division process corresponds to the process of S18 to S24.

<Other embodiments>
In addition, this embodiment can be changed and carried out as follows. The present embodiment and the following modifications can be implemented in combination with each other within a technically consistent range.

・ "About required injection amount"
The required injection amount Qd may be corrected by the learning value LAF in addition to the low temperature increase coefficient Kw, the transient correction amount ΔQ, and the feedback correction coefficient KAF. Incidentally, the calculation process of the learning value LAF is a process of inputting the feedback correction coefficient KAF and updating the learning value LAF so that the correction ratio of the base injection amount Qb by the feedback correction coefficient KAF becomes small. It is desirable that the learning value LAF is stored in an electrically rewritable non-volatile memory.

Further, for example, by feedforward control based on the disturbance fuel ratio, the required injection amount Qd may be calculated so that the required injection amount Qd becomes smaller when the disturbance fuel ratio is large than when it is small. Here, the disturbance fuel ratio is the ratio of the amount of fuel flowing into the combustion chamber 24 of the internal combustion engine 10 other than the fuel injected from the port injection valve 16 in one combustion cycle to the total amount of fuel flowing into the combustion chamber 24. be. Further, as the disturbance fuel, for example, a canister that collects fuel vapor from a fuel tank that stores fuel injected from the port injection valve 16 and an adjusting device that adjusts the inflow amount of the fluid in the canister to the intake passage 12. When the internal combustion engine is provided with the above, there is fuel vapor flowing from the canister into the intake passage 12. Further, for example, when a system for returning the fuel vapor in the crankcase to the intake passage 12 is provided, there is fuel vapor flowing into the intake passage 12 from the crankcase.

・ "About weight loss processing"
As described in the column of "Required injection amount", when the required injection amount is calculated according to the disturbance fuel ratio, the process of reducing the required injection amount by the disturbance fuel may be included in the reduction process.

・ "About intake asynchronous injection"
In the above embodiment, the intake asynchronous injection is performed so that the period during which the fuel injected from the port injection valve 16 reaches the position before the opening of the intake valve 18 falls within the valve closing period of the intake valve 18. However, it is not limited to this. For example, when the rotation speed NE is high and the asynchronous injection amount Qns is excessively large, the intake valve 18 is partially opened during the period in which the fuel injected from the port injection valve 16 reaches the position before the intake valve 18 is opened. It may overlap with the valve period.

・ "About intake synchronous injection"
In the above embodiment, the arrival end time is set based on the rotation speed NE, the filling efficiency η, the water temperature THW, and the intake phase difference DIN, but the present invention is not limited to this. For example, the injection start time Is may be set based on the rotation speed NE, the filling efficiency η, the water temperature THW, and the intake phase difference DIN. Further, as a parameter indicating the load, which is a parameter indicating the amount of fresh air filled in the combustion chamber 24, for example, the base injection amount Qb may be used instead of the filling efficiency η. Regarding the four parameters of rotation speed NE, load, water temperature THW, and intake phase difference DIN, the arrival end time and injection start time Is can be variably set based on only three of these parameters, or only two parameters. It may be variably set based on, or may be variably set based on only one parameter.

・ "About single injection processing"
In the above embodiment, the single injection process is performed so that the period during which the fuel injected from the port injection valve 16 reaches the position before the opening of the intake valve 18 falls within the valve closing period of the intake valve 18. However, it is not limited to this. For example, when the required injection amount Qd is large, a part of the period during which the fuel injected from the port injection valve 16 reaches the position before the opening of the intake valve 18 overlaps with the valve opening period of the intake valve 18. There may be. It is not essential to execute the single injection process.

・ "About selection process"
The execution conditions for the multi-injection process are not limited to the above conditions (a), (b) and (c). For example, the condition (a) above may be changed to the condition (d) that "Kw / KAF / Qb" is equal to or less than the specified amount. Here, the specified amount is set to a smaller value when the rotation speed NE is high than when it is low. In this case, the transient correction amount ΔQ can be a large value even when the multi-injection process is switched to by increasing the water temperature THW. That is, when the water temperature THW is low, the low temperature increase coefficient Kw becomes a large value, so that it is determined that the CPU 52 does not satisfy the above condition (d). On the other hand, when the water temperature THW rises slightly and the CPU 52 satisfies the condition of the above (d), the multi-injection process is switched to, but in that case, "Kw / KAF / Qb" is large. Therefore, the difference in the amount of fuel adhering to the intake passage 12 is large between when the single injection process is performed and when the multi-injection process is performed, and the absolute value of the transient correction amount ΔQ is large. Become.

・ "About the method of dividing the required injection amount"
In the above embodiment, the synchronous injection ratio Ks indicating the ratio of the synchronous injection amount Qs to the base injection amount Qb is variably set based on the rotation speed NE, the filling efficiency η, the water temperature THW, and the intake phase difference DIN. Not limited to. For example, the required injection amount Qd may be used instead of the filling efficiency η as the load parameter which is a parameter indicating the amount of fresh air filled in the combustion chamber 24. Further, the four parameters of the load parameter, the rotation speed NE, the water temperature THW, and the intake phase difference DIN can be variably set based on only three of them, or variably set based on only two parameters. It may be variably set based on only one parameter. At this time, it is desirable to variably set the load parameter and the water temperature THW by using at least one of them as much as possible. In addition to the above four parameters, for example, the intake pressure or the flow velocity of the intake air may be used. However, according to the above four parameters, the intake pressure and the flow velocity of the intake air can be grasped.

Further, it is not essential that the asynchronous injection ratio Kns is an amount indicating the ratio of the asynchronous injection amount Qns to the value obtained by subtracting the transient correction amount ΔQ from the required injection amount. For example, the asynchronous injection ratio Kns may be an amount indicating the ratio of the asynchronous injection amount Qns to the base injection amount Qb. In this case, "Kns + Ks = 1" is established. In this case, the final asynchronous injection amount Qns may be "Qb · Kns + Qb · (KAF · Kw-1) + ΔQ".

Further, it is not essential to determine the synchronous injection ratio Ks. For example, the synchronous injection amount Qs may be calculated based on the parameter in which the synchronous injection ratio Ks is determined in the above embodiment or a modification thereof. In this case, the asynchronous injection amount Qns may be "Qb, KAF, Kw + ΔQ-Qs".

For example, the value “KAF · Qb” in which the base injection amount Qb is corrected by the feedback correction coefficient KAF may be divided by the synchronous injection ratio Ks to obtain the synchronous injection amount Qs. In this case, the synchronous injection amount Qs is "Ks, KAF, Qb".

In the above embodiment, when the filling efficiency η is reduced, only the asynchronous injection amount Qns is reduced and corrected by the transient correction amount ΔQ, but the present invention is not limited to this. For example, only 1% of the transient correction amount ΔQ may be used as the reduction correction amount of the synchronous injection amount Qs.

In the above embodiment, when switching from the single injection process to the multi-injection process, only the asynchronous injection amount Qns is reduced and corrected by the transient correction amount ΔQ, but the present invention is not limited to this. For example, only 1% of the transient correction amount ΔQ may be allocated to the synchronous injection amount Qs.

・ "About the variable intake valve characteristics device"
The characteristic variable device that changes the characteristics of the intake valve 18 is not limited to the intake side valve timing adjusting device 44. For example, the lift amount of the intake valve 18 may be changed. In this case, the parameter indicating the valve characteristics of the intake valve 18 is a lift amount or the like instead of the intake phase difference DIN.

・ "About fuel injection control device"
The fuel injection control device is not limited to the one provided with the CPU 52 and the ROM 54 to execute software processing. For example, a dedicated hardware circuit (for example, ASIC or the like) for hardware processing of at least a part of the software processed in the above embodiment may be provided. That is, the fuel injection control device may have any of the following configurations (a) to (c). (A) A processing device that executes all of the above processing according to a program and a program storage device such as a ROM for storing the program are provided. (B) A processing device and a program storage device that execute a part of the above processing according to a program, and a dedicated hardware circuit for executing the remaining processing are provided. (C) A dedicated hardware circuit for executing all of the above processes is provided. Here, there may be a plurality of software processing circuits including a processing device and a program storage device, and a plurality of dedicated hardware circuits. That is, the processing may be performed by a processing circuit comprising at least one of one or more software processing circuits and one or more dedicated hardware circuits.

·"others"
For example, in the case of providing a device capable of changing and controlling the injection pressure of the port injection valve 16, if a negative judgment is made once in the processing of S26, the next cylinder should be positively judged in the processing of S26. , The reduction control of the injection pressure may be executed.

It is not essential that the internal combustion engine 10 is provided with a characteristic variable device that changes the characteristics of the intake valve 18. It is not essential that the internal combustion engine 10 includes a throttle valve 14.

10 ... Internal combustion engine, 12 ... Intake passage, 14 ... Throttle valve, 16 ... Port injection valve, 18 ... Intake valve, 20 ... Cylinder, 22 ... Piston, 24 ... Combustion chamber, 26 ... Ignition device, 28 ... Crank shaft, 30 ... Exhaust valve, 32 ... Exhaust passage, 34 ... Catalyst, 38 ... Timing chain, 40 ... Intake side camshaft, 42 ... Exhaust side camshaft, 44 ... Intake side valve timing adjustment device, 50 ... Control device, 52 ... CPU, 54 ... ROM, 60 ... Crank angle sensor, 62 ... Air flow meter, 64 ... Air-fuel ratio sensor, 66 ... Intake side cam angle sensor, 68 ... Water temperature sensor, 76 ... Power supply circuit.

Claims (4)

Applicable to internal combustion engines equipped with a port injection valve that injects fuel into the intake passage.
The required injection amount calculation process for calculating the required injection amount for controlling the air-fuel ratio to the target air-fuel ratio based on the fresh air amount filled in the cylinder of the internal combustion engine, and
Intake synchronous injection in which the port injection valve is operated to inject the fuel of the required injection amount in synchronization with the valve opening period of the intake valve, and the timing on the advance side of the intake synchronous injection. Multi-injection processing that executes intake asynchronous injection that injects fuel at
Even if the amount of fresh air to be filled is the same, if the predetermined conditions are satisfied, the weight reduction process for reducing the required injection amount and the weight reduction process.
When the asynchronous injection amount, which is the injection amount of the intake asynchronous injection determined from the required injection amount reduced by the reduction process, is less than the minimum injection amount allowed by the port injection valve, the asynchronous injection amount is set to the minimum injection amount. The double-sided correction process of increasing the amount so as to be as described above and decreasing the synchronous injection amount, which is the injection amount of the intake synchronous injection, is executed .
In both correction processing, the difference between the asynchronous injection amount and the minimum injection amount before correction is used as the increase correction amount of the asynchronous injection amount and the decrease correction amount of the synchronous injection amount.
A selection process for selecting either a single injection process for injecting the required injection amount of fuel by the intake asynchronous injection or a multi-injection process by operating the port injection valve is executed.
The selection process is a fuel injection control device for an internal combustion engine including a process of selecting the single injection process when the synchronous injection amount reduced by the reduction correction amount is less than the minimum injection amount. Applicable to internal combustion engines equipped with a port injection valve that injects fuel into the intake passage.
The required injection amount calculation process for calculating the required injection amount for controlling the air-fuel ratio to the target air-fuel ratio based on the fresh air amount filled in the cylinder of the internal combustion engine, and
Intake synchronous injection in which the port injection valve is operated to inject the fuel of the required injection amount in synchronization with the valve opening period of the intake valve, and the timing on the advance side of the intake synchronous injection. Multi-injection processing that executes intake asynchronous injection that injects fuel at
Even if the amount of fresh air to be filled is the same, if the predetermined conditions are satisfied, the weight reduction process for reducing the required injection amount and the weight reduction process.
When the asynchronous injection amount, which is the injection amount of the intake asynchronous injection determined from the required injection amount reduced by the reduction process, is less than the minimum injection amount allowed by the port injection valve, the asynchronous injection amount is set to the minimum injection amount. Both correction processing that increases the amount so as to be as described above and decreases the synchronous injection amount, which is the injection amount of the intake synchronous injection.
The single injection process of operating the port injection valve to inject the fuel of the required injection amount by the intake asynchronous injection and the selection process of selecting one of the multi-injection process are executed.
The predetermined condition includes a condition that the state in which the single injection process is selected by the selection process is switched to the state in which the multi-injection process is selected.
In the weight reduction process, when the state in which the single injection process is selected by the selection process is switched to the state in which the multi-injection process is selected, the transient injection amount is reduced by reducing the asynchronous injection amount. Fuel injection control device for internal combustion engine including correction processing. Applicable to internal combustion engines equipped with a port injection valve that injects fuel into the intake passage.
The required injection amount calculation process for calculating the required injection amount for controlling the air-fuel ratio to the target air-fuel ratio based on the fresh air amount filled in the cylinder of the internal combustion engine, and
Intake synchronous injection in which the port injection valve is operated to inject the fuel of the required injection amount in synchronization with the valve opening period of the intake valve, and the timing on the advance side of the intake synchronous injection. Multi-injection processing that executes intake asynchronous injection that injects fuel at
Even if the amount of fresh air to be filled is the same, if the predetermined conditions are satisfied, the weight reduction process for reducing the required injection amount and the weight reduction process.
When the asynchronous injection amount, which is the injection amount of the intake asynchronous injection determined from the required injection amount reduced by the reduction process, is less than the minimum injection amount allowed by the port injection valve, the asynchronous injection amount is set to the minimum injection amount. Both correction processing that increases the amount so as to be as described above and decreases the synchronous injection amount, which is the injection amount of the intake synchronous injection .
A division process for dividing the required injection amount into the asynchronous injection amount and the synchronous injection amount is executed.
The weight reduction process is a fuel injection control device for an internal combustion engine, which is a process for reducing the weight only for the asynchronous injection amount. The predetermined condition includes a condition that the amount of fresh air is reduced.
The internal combustion engine according to any one of claims 1 to 3, wherein the weight reduction process includes a transient correction process for reducing the required injection amount by reducing the asynchronous injection amount when the fresh air amount decreases. Fuel injection control device.

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