JP2014227947A - Fuel injection control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel injection control device of an internal combustion engine which can perform an engine operation in a favorable combustion state by selecting a proper requirement injection pattern.SOLUTION: A device performs fuel injection from an in-cylinder injection valve in one combustion cycle by multistage injection for dividedly performing fuel injection a plurality of times by performing the operation control of the in-cylinder injection valve on the basis of a requirement injection pattern which is set according to an engine operation region. In the engine operation region in which a plurality of the requirement injection patterns are set, the requirement injection pattern among the requirement injection patterns in which the execution timing of the last stage injection of multistage injection is the most approximate to a compression top dead point is preferentially selected. The operation control of the in-cylinder injection valve is performed on the basis of the selected requirement injection pattern.

Description

  The present invention relates to a fuel injection control device for an internal combustion engine having an in-cylinder injection valve that directly injects fuel into a combustion chamber.

  In general, in a fuel injection control device for an internal combustion engine provided with an in-cylinder injection valve, an injection start timing and an injection time are set based on the operating state (rotation speed of the output shaft, load, etc.) of the internal combustion engine. The in-cylinder injection valve is driven to open based on the injection start timing and the injection time. Thus, an amount of fuel corresponding to the engine operating state is injected from the in-cylinder injection valve.

  In recent years, an apparatus has been proposed in which fuel injection from such an in-cylinder injection valve is performed by multistage injection in which fuel injection is performed in a plurality of times in one combustion cycle (see Patent Document 1). In the apparatus of Patent Document 1, the required value of the injection pattern in the multistage injection (the number of injection stages and the start timing of each injection) is set based on the engine operating state.

JP 2012-13054 A

  Here, in the above-described apparatus for performing multi-stage injection, it is not limited to preparing one required injection pattern for each engine operating region, for example, those regions for convenience of setting the engine operating region in which the required injection pattern is individually determined. It is conceivable that a plurality of required injection patterns are set in the same engine operation region, for example, when a part of the engine is overlapped. In this case, if an appropriate pattern is not selected from a plurality of required injection patterns, there is a possibility that a required injection pattern that causes deterioration of the combustion state may be selected even though there are other appropriate patterns.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a fuel injection control device for an internal combustion engine that can realize an engine operation in a good combustion state by selecting an appropriate required injection pattern. It is to provide.

  A fuel injection control device for an internal combustion engine for solving the above-described problem includes an in-cylinder injection valve that directly injects fuel into a combustion chamber, and controls the operation of the in-cylinder injection valve based on a required injection pattern according to an engine operating region. Then, fuel injection from the in-cylinder injection valve in one combustion cycle is performed by multi-stage injection in which fuel injection is performed in a plurality of times. In the specific engine operation region in which a plurality of the required injection patterns are set, this apparatus is a required injection in which the execution timing of the final stage injection of the multistage injection is the closest to the compression top dead center among the required injection patterns. A pattern is preferentially selected and operation control of the in-cylinder injection valve is executed.

  A fuel injection control device for an internal combustion engine for solving the above-described problem includes an in-cylinder injection valve that directly injects fuel into a combustion chamber, and controls the operation of the in-cylinder injection valve based on a required injection pattern according to an engine operating region. Then, fuel injection from the in-cylinder injection valve in one combustion cycle is performed by multi-stage injection in which fuel injection is performed in a plurality of times. In the specific engine operation region in which a plurality of the required injection patterns are set, this apparatus is a required injection in which the execution timing of the final stage injection of the multistage injection is the closest to the compression top dead center among the required injection patterns. The pattern is selected and the operation control of the in-cylinder injection valve is executed.

  In an internal combustion engine having an in-cylinder injection valve, the closer the execution timing of fuel injection by the in-cylinder injection valve is to the compression top dead center, the shorter the time for the injected fuel to diffuse in the combustion chamber and the higher the fuel concentration portion is formed. Therefore, a portion having a higher fuel concentration is easily formed in the vicinity of the portion where the fuel is ignited in the combustion chamber as compared with the surrounding portion. And, by igniting the fuel at a portion where the fuel concentration is moderately high, the initial combustion speed can be increased to improve the combustion state of the fuel, and the fuel efficiency can be improved.

  According to the above apparatus, when a plurality of required injection patterns are set during engine operation, the execution timing of the final stage injection of the multistage injection is close to the compression top dead center, that is, suitable for obtaining a good combustion state. The required injection pattern can be selected so that it is time. Therefore, according to the above apparatus, even when a plurality of required injection patterns are set during engine operation, it is possible to select an appropriate injection pattern and realize engine operation in a good combustion state.

  In the above apparatus, in the specific engine operation region, the first required injection pattern in which the execution timing of the last stage injection is the first time closest to the compression top dead center, and the execution timing of the last stage injection are the A second required injection pattern that is a second time before the first time can be set. In the specific engine operation region, when the engine is in an engine operation state in which the first request injection pattern can be selected, the first request injection pattern is selected, and the engine operation state in which the first request injection pattern cannot be selected. If so, the second required injection pattern can be selected.

  According to the above apparatus, in the engine operating region in which the first required injection pattern that is most suitable for obtaining a good combustion state and the second required injection pattern that is the second most suitable are defined, Any one of the required injection patterns can be appropriately selected according to the situation, such as selecting the required injection pattern and exceptionally selecting the second required injection pattern when the same pattern cannot be selected.

  In the above apparatus, when there are a plurality of required injection patterns in which the execution timing of the last stage injection is closest to the compression top dead center, the required injection pattern includes the total injection amount in one combustion cycle. It is possible to select the required injection pattern in which the ratio of the injection amount by the last stage injection is the largest.

  According to the above apparatus, when there are a plurality of required injection patterns in which the execution timing of the last stage injection in the multistage injection is closest to the compression top dead center, the compression top dead center suitable for obtaining a good combustion state is obtained. It is possible to select a required injection pattern in which the proportion of the injection amount by fuel injection executed at a near time is large. As described above, even when there are a plurality of required injection patterns with the same execution timing of the last stage injection in the multistage injection, the ratio of the injection quantity by the last stage injection to the total injection quantity is considered appropriately. By selecting a proper injection pattern, it is possible to realize engine operation in a good combustion state.

  In the above apparatus, the intake stroke and the compression stroke of the internal combustion engine can be partitioned in advance into a plurality of periods, and a combination of whether or not injection is performed in these periods can be determined by the required injection pattern.

In the above apparatus, the plurality of periods can be set to four periods of the first half of the intake stroke, the second half of the intake stroke, the first half of the compression stroke, and the second half of the compression stroke.
In the above apparatus, a priority for selection is set for each required injection pattern, and in a specific operation region, the execution timing of the last stage injection of the multistage injection is closest to the compression top dead center according to the priority. It is preferable to preferentially select the required injection pattern that is the time.

  According to the above apparatus, for each requested injection pattern, such as selecting the requested injection pattern with the highest priority, or exceptionally selecting the requested injection pattern with the second highest priority when the same pattern cannot be selected. Any one of the plurality of required injection patterns can be appropriately selected based on the set priority.

1 is a schematic diagram showing a schematic configuration of an embodiment of a fuel injection control device for an internal combustion engine. The timing chart which shows an example of the execution aspect of multistage injection with each period. 6 is a schematic diagram showing each engine operation region in which a required injection pattern is set. The table | surface which shows the relationship between each engine operation area | region and a request | requirement injection pattern. The flowchart which shows the execution procedure of a selection process.

Hereinafter, an embodiment of a fuel injection control device for an internal combustion engine will be described.
As shown in FIG. 1, a throttle mechanism 12 is provided in the intake passage 11 of the internal combustion engine 10. The throttle mechanism 12 includes a throttle valve 13 and a throttle motor 14. Then, the opening degree of the throttle valve 13 (throttle opening degree TA) is adjusted through the operation control of the throttle motor 14, whereby the amount of air (intake air amount GA) taken into the combustion chamber 15 through the intake passage 11 is adjusted. Adjusted.

  The intake passage 11 is provided with a passage injection valve 16. The passage injection valve 16 injects fuel into the intake passage 11 (specifically, the intake port 11a) as the valve is opened. The internal combustion engine 10 is provided with an in-cylinder injection valve 17 in addition to the passage injection valve 16. The in-cylinder injection valve 17 injects fuel inside the combustion chamber 15 of the internal combustion engine 10 as the valve is opened.

  In the combustion chamber 15 of the internal combustion engine 10, an air-fuel mixture composed of intake air and injected fuel is ignited and burned by an ignition operation by the spark plug 26. By this combustion, the piston 18 reciprocates and the crankshaft 19 rotates. The air-fuel mixture after combustion is sent out from the combustion chamber 15 to the exhaust passage 20 as exhaust.

  The internal combustion engine 10 is provided with a fuel supply system for supplying fuel to the passage injection valve 16 and the in-cylinder injection valve 17. The fuel supply system includes a fuel tank 21 that stores fuel, a feed pump 23 that pumps fuel in the fuel tank 21 to the low-pressure fuel passage 22, and pumps fuel in the low-pressure fuel passage 22 to the high-pressure fuel passage 24. And a high-pressure pump 25. In the present embodiment, the pressure of the fuel supplied from the high-pressure pump 25 to the high-pressure fuel passage 24, in other words, the in-cylinder injection valve 17 is controlled by controlling the opening and closing timing of the relief valve built in the high-pressure pump 25. The injection pressure is adjusted.

  The internal combustion engine 10 includes an electronic control device 40 configured to include a microcomputer, for example. The electronic control device 40 receives detection signals from various sensors for detecting the operating state of the internal combustion engine 10. The various sensors include a crank sensor for detecting the rotation angle (crank angle) and rotation speed (engine rotation speed NE) of the crankshaft 19, and an operation amount (accelerator operation amount ACC) of an accelerator operation member (not shown). An accelerator sensor for detection and a throttle sensor for detecting the opening of the throttle valve 13 (throttle opening TA) are provided. In addition, an air flow meter for detecting the intake air amount GA, a pressure sensor for detecting the pressure of the fuel in the high-pressure fuel passage 24 (actual injection pressure P), and the like are also provided.

  The electronic control unit 40 performs various calculations based on detection signals from various sensors, and executes engine control such as throttle control, injection pressure control, and fuel injection control based on the calculation results.

  The throttle control is executed as follows. That is, a control target value (target throttle opening) of the throttle opening TA is set based on the accelerator operation amount ACC and the engine speed NE, and the target throttle opening and the actual throttle opening TA coincide with each other. Operation control of the throttle motor 14 is executed. In the present embodiment, the amount of air taken into the combustion chamber 15 of the internal combustion engine 10 is adjusted through such throttle control.

  The injection pressure control is executed as follows. That is, the control target value (target injection pressure) of the fuel pressure in the high-pressure fuel passage 24 is calculated based on the engine load KL and the engine speed NE, and the relief is performed so that the actual injection pressure P becomes the target injection pressure. The opening and closing timing of the valve is adjusted. Through such injection pressure control, the injection pressure of the in-cylinder injection valve 17 is adjusted to a pressure corresponding to the engine operating state. In the present embodiment, a value (GA / NE) obtained by dividing the intake air amount GA by the engine rotational speed NE is used as the engine load KL. As the engine load KL, an intake air amount GA, a fuel injection amount, or a value obtained by dividing the fuel injection amount by the engine rotational speed NE can be used.

The fuel injection control is basically executed as follows.
First, the fuel injection amount at which the air-fuel ratio of the air-fuel mixture used for combustion in the combustion chamber 15 with respect to the intake air amount GA becomes a desired ratio (for example, the theoretical air-fuel ratio) is a control target value (requested injection amount Tq). ). Further, the fuel injection ratio (port injection rate Rp [0 ≦ Rp ≦ 1.0]) from the passage injection valve 16 is calculated based on the engine load KL and the engine speed NE.

  Then, an amount (Tq × Rp) obtained by multiplying the required injection amount Tq by the port injection rate Rp is calculated as a control target value (target port injection amount) of the fuel injection amount from the passage injection valve 16. Then, the passage injection valve 16 is driven to open so that the same amount of fuel as the target port injection amount is injected. Specifically, a control target value for fuel injection timing (target port injection timing) and a control target value for fuel injection time (target port injection time) are calculated based on the target port injection amount and the engine speed NE. The passage injection valve 16 is driven to open based on the target port injection timing and the target port injection time.

  On the other hand, an amount (Tq × [1.0−Rp]) obtained by multiplying the required injection amount Tq by the fuel injection ratio (= 1.0−Rp) from the in-cylinder injection valve 17 is the fuel injection from the in-cylinder injection valve 17. The amount is calculated as a control target value (target in-cylinder injection amount Tqc). Then, the in-cylinder injection valve 17 is driven to open so that the same amount of fuel as the target in-cylinder injection amount Tqc is injected.

  In the present embodiment, fuel injection from the in-cylinder injection valve 17 in one combustion cycle is performed by multistage injection in which fuel injection is performed in a plurality of times. Specifically, as shown in FIG. 2, the intake stroke and the compression stroke of the internal combustion engine 10 are “the first half of the intake stroke (fourth period)”, “the second half of the intake stroke (third period)”, “the first half of the compression stroke ( (Second period) ”and“ second half of the compression stroke (first period) ”. And the request | requirement injection pattern which combined the presence or absence of execution of the fuel injection in those periods is preset. A plurality of required injection patterns are set, and each required injection pattern is stored in the electronic control unit 40. FIG. 2 shows an example in which fuel injection from the in-cylinder injection valve 17 is executed in the first period, the third period, and the fourth period.

  When executing the fuel injection control, one of the required injection patterns is selected based on the engine load KL and the engine rotational speed NE. Further, based on the engine operating state (target in-cylinder injection amount Tqc, engine rotation speed NE, actual injection pressure P), the control target value (target in-cylinder injection) of the fuel injection timing for each injection determined in the required injection pattern. Time) and a control target value (target in-cylinder injection time) of the fuel injection time are calculated. For each injection, the in-cylinder injection valve 17 is driven to open based on the target in-cylinder injection timing and the target in-cylinder injection time.

  In the present embodiment, the fuel injection in the first period of the first half of the intake stroke is performed by injecting fuel toward the top surface of the piston 18 and cooling the top surface with the injected fuel, thereby reducing the temperature in the combustion chamber 15. And has the function of improving the intake efficiency. The fuel injection in the second period of the latter half of the intake stroke has a function of strengthening the air flow when the moving speed of the piston 18 decreases and the air flow in the combustion chamber 15 becomes weak. Further, the fuel injection in the third period of the first half of the compression stroke has a function of cooling the in-cylinder injection valve 17 with the fuel that passes through the in-cylinder injection valve 17 during the execution. Further, the fuel injection in the fourth period in the latter half of the compression stroke has a function of increasing the ignitability of the air-fuel mixture and increasing the combustion speed by collecting the injected fuel around the spark plug 26.

  Through such fuel injection control, an amount of fuel commensurate with the operation state of the internal combustion engine 10 at that time is injected from the passage injection valve 16 and the in-cylinder injection valve 17 in an injection pattern suitable for the operation state, and the combustion chamber of the internal combustion engine 10 15 is supplied.

FIG. 3 shows each engine operation region where the required injection pattern is set, and FIG. 4 shows the relationship between each engine operation region and the required injection pattern.
As shown in FIG. 3 or FIG. 4, in the apparatus of the present embodiment, the engine operating areas determined by the engine load KL and the engine speed NE are “Area A”, “Area B”, “Area C”, “Area D”. And “area E” is divided into five injection areas, and different required injection patterns are set for the respective injection areas.

  As the region A, an engine operation region where the engine load KL is large and the engine speed NE is low is defined. In this region A, a first required injection pattern for requesting execution of fuel injection from the in-cylinder injection valve 17 in the first period and the fourth period is set. In this region A, two-stage fuel injection from the in-cylinder injection valve 17 is executed. In the region A, fuel injection from the passage injection valve 16 is not executed.

  The region B is an engine operation region where the engine load KL is large and the engine rotational speed NE is low, and an engine operation region including the region A is defined. In this region B, a second required injection pattern for requesting execution of fuel injection from the in-cylinder injection valve 17 in the third period and the fourth period is set. In this region B, two-stage fuel injection from the in-cylinder injection valve 17 is executed. In region B, fuel injection from the passage injection valve 16 is not executed.

  As the region C, an engine operation region where the engine rotational speed NE is high is defined. In this region C, a third required injection pattern for executing fuel injection from the cylinder injection valve 17 only in the fourth period is set. That is, in the region C, one-stage fuel injection from the in-cylinder injection valve 17 is executed. In this region C, fuel injection from the passage injection valve 16 is not executed.

  As the region D, an engine operation region in which the engine load KL is medium and the engine rotational speed NE is low is defined. In this region D, a fourth required injection pattern for executing fuel injection from the in-cylinder injection valve 17 only in the fourth period is set. In this region D, similarly to the region C, one-stage fuel injection from the in-cylinder injection valve 17 is executed. However, in this region D, fuel injection from the passage injection valve 16 is also performed.

  As the region E, an engine operation region in which the engine load KL is small and the engine rotational speed NE is low is defined. In this region E, fuel injection from the cylinder injection valve 17 is not executed in any of the first to fourth periods, and only fuel injection from the passage injection valve 16 is executed.

  As is apparent from FIG. 3, in the apparatus of the present embodiment, an engine operation region including the region A is defined as the region B, and a required injection pattern is defined in each of the regions A and B. Therefore, two required injection patterns are set in a portion where regions A and B overlap (portion corresponding to region A). In addition, the regions B, C, D, and E are set so that the adjacent regions partially overlap (portions indicated by broken lines in the drawing). A plurality of required injection patterns are defined in the overlapping portion of such areas. As described above, in the apparatus according to the present embodiment, a plurality of required injection patterns may be set in the same engine operation region. Therefore, if an appropriate pattern is not selected from these required injection patterns, other appropriate patterns In spite of this, there is a risk of selecting a requested injection pattern that causes deterioration of the combustion state. In the present embodiment, an engine operation region in which a plurality of regions A to E overlap each other corresponds to a specific engine operation region.

  In the apparatus of the present embodiment, among the plurality of required injection patterns set in the same engine operation region, the required injection pattern in which the period including the execution timing of the final stage injection of the multistage injection is the period closest to the compression top dead center Is preferentially selected, and the operation control of the in-cylinder injection valve 17 is executed. In the region C and region D in which one stage of fuel injection is set in the required injection pattern, the period during which the fuel injection is executed (fourth period) is used as the period including the execution timing of the last stage injection of the multistage injection. It is done.

  In the internal combustion engine 10, as the execution timing of the fuel injection by the in-cylinder injection valve 17 is closer to the compression top dead center, the time during which the injected fuel diffuses in the combustion chamber 15 is shortened and a portion with a high fuel concentration is easily formed. Therefore, it becomes easier to form a portion having a higher fuel concentration in the combustion chamber 15 in the vicinity of the spark plug 26 than in the peripheral portion. Then, by performing the ignition operation with the spark plug 26 in a state where the surrounding fuel concentration is moderately high, the initial combustion speed of the fuel in the combustion chamber 15 can be increased, and the combustion state of the fuel can be improved. As a result, it becomes possible to improve fuel efficiency.

  As shown in FIG. 4, in the apparatus according to the present embodiment, the priority for selecting the required injection pattern is determined in advance. Specifically, the pattern having the highest priority is the first required injection pattern (region A), the second required injection pattern (region B), the third required injection pattern (region C), and the fourth request. The priorities are determined so that the priorities become lower in the order of the injection pattern (region D) and the fifth required injection pattern (region E) in which fuel injection by the in-cylinder injection valve 17 is not performed.

  In the engine operation region where a plurality of required injection patterns are set, the required injection pattern is selected as follows based on the priority. That is, the second required injection pattern corresponding to the region B is selected in the overlapping portion of the regions B and C and the overlapping portion of the regions B, C, and D. In addition, the third required injection pattern corresponding to the region C is selected in the overlapping portion of the regions C and D, the overlapping portion of the regions C, D, and E, and the overlapping portion of the regions C and E. Furthermore, the fourth required injection pattern corresponding to the region D is selected in the overlapping portion of the regions D and E.

  As described above, when a plurality of required injection patterns are set during the operation of the internal combustion engine 10, by selecting the required injection pattern having a high priority, the execution timing of the last stage injection of the multi-stage injection becomes the compression top dead center. The required injection pattern can be selected so as to be the time closest to, that is, the time suitable for obtaining a good combustion state. Therefore, even when a plurality of required injection patterns are set during operation of the internal combustion engine 10, it is possible to select an appropriate injection pattern and realize engine operation in a good combustion state.

  In the present embodiment, in the region C and the region D, the period including the execution timing of the last stage injection of the multistage injection is the same fourth period. Therefore, in the engine operation region where the region C and the region D overlap, it is not possible to determine the priority only in the period in which the last stage injection is executed. In the present embodiment, among the third and fourth required injection patterns set in the overlapping portions of the regions C and D, the fourth injection period is the fourth period with respect to the total injection amount (required injection amount Tq) in one combustion cycle. The third required injection pattern with the larger proportion of the injection amount due to the fuel injection is selected.

  In the present embodiment, in the region C, only fuel injection in the fourth period by the in-cylinder injection valve 17 is executed, whereas in region D, passage injection is performed in accordance with the fuel injection in the fourth period by the in-cylinder injection valve 17. Fuel injection from the valve 16 is also executed. Therefore, in regions C and D, the proportion of the injection amount by fuel injection in the fourth period to the required injection amount Tq is compared with region D even though the period in which the last stage injection is performed is the same fourth period. Thus, there are many areas C. In view of this point, in the present embodiment, the priority of the third injection pattern corresponding to the region C when selecting the required injection pattern is higher than the priority of the fourth required injection pattern corresponding to the region D. Is set.

  Thereby, in the overlapping part of the region C and the region D, the third required injection pattern for performing only the fuel injection by the in-cylinder injection valve 17 in the fourth period, that is, the fuel injection that is executed at a time close to the compression top dead center Therefore, the required injection pattern suitable for obtaining a good combustion state can be selected. As described above, according to the apparatus of the present embodiment, even when there are a plurality of required injection patterns having the same period in which the final injection in the multi-stage injection is performed, the injection amount by the final injection with respect to the required injection amount Tq is reduced. By considering the proportion, it is possible to select an appropriate injection pattern and realize engine operation in a good combustion state.

  In the present embodiment, the region B is set to the engine operation region including the region A. The first injection pattern including the fuel injection in the first period is set in the region A, and the fuel injection in the third period and the fuel injection in the fourth period before the first period are set in the region B. A second required injection pattern is set. The priority of the first required injection pattern corresponding to the region A is set higher than the priority of the second required injection pattern corresponding to the region B. In the present embodiment, the fuel injection execution time in the first period of the first required injection pattern corresponds to the first time, and the fuel injection execution time in the third period of the second required injection pattern is the first time. This corresponds to the second period before the period.

  In the present embodiment, when the engine operation region is the region A, whether or not an execution condition for determining whether or not to perform fuel injection from the in-cylinder injection valve 17 in the first required injection pattern is satisfied. Is judged. This execution condition is determined to be satisfied when the actual injection pressure P is equal to or higher than the predetermined pressure, while it is determined not to be satisfied when the actual injection pressure P is less than the predetermined pressure.

  If the execution condition is satisfied when the engine operation region is the region A, the first request injection pattern is selected as the engine operation in the first request injection pattern is possible. Fuel injection from the in-cylinder injection valve 17 is executed. Thereby, it is possible to execute the fuel injection from the in-cylinder injection valve 17 by selecting an injection pattern that can expect an engine operation in a good combustion state.

  On the other hand, if the execution condition is not satisfied when the engine operation region is the region A, it is assumed that the engine operation based on the first required injection pattern cannot be performed, so that it overlaps with the region A. The second required injection pattern corresponding to the region B is selected, and fuel injection from the in-cylinder injection valve 17 is executed in the same pattern. Thereby, when it becomes impossible to select the first required injection pattern in which the engine operation in the best combustion state can be expected, the second required injection pattern in which the engine operation in the second best combustion state can be expected. And the fuel injection from the in-cylinder injection valve 17 can be executed.

  As described above, according to the apparatus of the present embodiment, in the region A in which the first required injection pattern and the second required injection pattern are defined, the first required injection pattern is normally selected and the same pattern is selected. If the second required injection pattern is exceptionally selected when it is not possible, one of these required injection patterns can be appropriately selected according to the situation.

Hereinafter, the procedure for selecting the required injection pattern in this manner will be described in detail.
FIG. 5 shows an execution procedure of processing (selection processing) for selecting a required injection pattern. The series of processes shown in the flowchart of FIG. 11 is a process that forms part of the process related to the fuel injection control, and is executed by the electronic control unit 40 as an interrupt process at predetermined intervals.

  As shown in FIG. 5, in the selection process, first, the engine operating state determined by the engine load KL and the engine rotational speed NE is a state where a plurality of required injection patterns are set (in detail, the region A or hatched in FIG. It is determined whether or not the state is included in the region (step S11). When the engine operating state is set with only one required injection pattern (step S11: NO), the present process is temporarily terminated without executing the following process.

When the engine operating state is set with a plurality of required injection patterns (step S11: YES), it is determined whether or not the engine operating state is included in the region A (step S12).
When the engine operating state at this time is included in the region A (step S12: YES), it is determined whether or not the execution condition is satisfied (step S13). When the execution condition is satisfied (step S13: YES), the first required injection pattern corresponding to the region A is selected (step S14). As a result, the first required injection pattern that provides the best combustion state is selected, and fuel injection from the in-cylinder injection valve 17 is executed.

  On the other hand, when the execution condition is not satisfied (step S13: NO), the second requested injection pattern corresponding to the region B is selected (step S15). As a result, the second required injection pattern that is the second most suitable for obtaining a good combustion state is selected, and fuel injection from the in-cylinder injection valve 17 is executed.

  When the engine operating state is set with a plurality of required injection patterns (step S11: YES), if the engine operating state is not included in the region A (step S12: NO), it is set at this time. The priority of the required injection pattern (see FIG. 4) is calculated separately. Then, the required injection pattern with the highest priority is selected by comparing the priorities (step S16). As a result, the required injection pattern that provides the best combustion state is selected, and fuel injection from the in-cylinder injection valve 17 is executed. In the present embodiment, a map that defines the relationship between each required injection pattern and its priority is stored in advance in the electronic control unit 40. In the process of step S16, the priority of each requested injection pattern is calculated based on this map.

As described above, according to the present embodiment, the following effects can be obtained.
(1) Among the plurality of required injection patterns set in the same engine operation region, the required injection pattern whose period including the execution timing of the final stage injection of the multistage injection is the period closest to the compression top dead center is given priority. The control of the cylinder injection valve 17 is selected and executed. Therefore, even when a plurality of required injection patterns are set during operation of the internal combustion engine 10, it is possible to select an appropriate injection pattern and realize engine operation in a good combustion state.

  (2) When the engine operating state is included in the region A, the first required injection pattern is selected when the execution condition is satisfied, and when the execution condition is not satisfied, the region B overlaps with the region A. The second required injection pattern is selected. Therefore, in the region A, the first required injection pattern is selected in the normal state, and when the same pattern cannot be selected, the second required injection pattern is exceptionally selected according to the situation. Can be selected appropriately.

  (3) Of the third and fourth required injection patterns set in the engine operation region where region C and region D overlap, the total injection amount (required injection amount Tq) in one combustion cycle Thus, the third required injection pattern with the larger proportion of the fuel injection amount in the fourth period is selected. For this reason, although there are a plurality of required injection patterns in which the last stage injection in the multi-stage injection is performed, an appropriate injection pattern can be obtained by considering the ratio of the injection amount by the last stage injection to the required injection amount Tq. It is possible to realize the engine operation in a good combustion state by selecting.

The above embodiment may be modified as follows.
Instead of calculating the priority of each required injection pattern based on the map, an arithmetic expression for calculating the priority is stored in advance in the electronic control unit 40 and the priority is calculated based on the arithmetic expression. You may do it.

  -In the overlapping part of the regions C and D, the required injection pattern is not limited to selecting the required injection pattern in which the ratio of the fuel injection amount in the fourth period to the required injection amount Tq is larger, but based on any selection criterion Can be selected. By selecting the required injection pattern in which the ratio of the fuel injection executed in the period close to the compression top dead center in the entire period (intake stroke and compression stroke) is selected, the operational effect according to the above embodiment is obtained. It is done.

  If the fuel injection from the in-cylinder injection valve 17 in the first required injection pattern in the region A can be properly executed, in the same region A, the first and second required injection patterns Instead of preferentially selecting the first required injection pattern, the first required injection pattern may always be selected. Even with such an apparatus, when a plurality of required injection patterns are set during operation of the internal combustion engine 10, it is possible to select an appropriate injection pattern and realize engine operation in a good combustion state.

  -As a period for executing fuel injection at each stage of multi-stage injection, two periods are set for the intake stroke and the compression stroke of the internal combustion engine 10, three periods are set, or five or more periods are set. can do.

  In the apparatus of the above embodiment, the intake stroke and the compression stroke of the internal combustion engine 10 are divided in advance into a plurality of periods, and multistage injection is executed based on a requested injection pattern that combines the presence or absence of fuel injection in those periods. . Not only this but the apparatus of the said embodiment can be applied also to the apparatus which performs multistage injection based on the request | requirement injection pattern which combined pilot injection and after-injection with main injection after changing the structure suitably. . In such an apparatus, as a selection parameter for selecting the required injection pattern, not only the period including the execution timing of the final stage injection of the multistage injection but also the execution timing of the final stage injection of the multistage injection can be used. That is, in the engine operation region in which a plurality of required injection patterns are set, the required injection pattern in which the execution timing of the final injection of the multi-stage injection is closest to the compression top dead center is preferentially selected, and the in-cylinder injection valve 17 operation controls can be executed. As the execution timing of the last stage injection of the multi-stage injection, the execution start timing or the execution stop timing of the last stage injection can be employed.

  -The apparatus of the said embodiment can be applied to the apparatus in which the channel | path injection valve 16 is not provided, after changing a structure suitably.

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 11 ... Intake passage, 11a ... Intake port, 12 ... Throttle mechanism, 13 ... Throttle valve, 14 ... Throttle motor, 15 ... Combustion chamber, 16 ... Passage injection valve, 17 ... In-cylinder injection valve, 18 ... Piston, 19 ... crankshaft, 20 ... exhaust passage, 21 ... fuel tank, 22 ... low pressure fuel passage, 23 ... feed pump, 24 ... high pressure fuel passage, 25 ... high pressure pump, 26 ... spark plug, 40 ... electronic control device.

Claims (7)

An in-cylinder injection valve that directly injects fuel into the combustion chamber is provided. In a fuel injection control device for an internal combustion engine that performs fuel injection from the in-cylinder injection valve in a single combustion cycle,
In the specific engine operation region in which a plurality of the required injection patterns are set, the apparatus performs required injection in which the execution timing of the final stage injection of the multistage injection is the closest to the compression top dead center among the required injection patterns. A fuel injection control device for an internal combustion engine, wherein a pattern is preferentially selected and operation control of the in-cylinder injection valve is executed. An in-cylinder injection valve that directly injects fuel into the combustion chamber is provided. In a fuel injection control device for an internal combustion engine that performs fuel injection from the in-cylinder injection valve in a single combustion cycle,
In the specific engine operation region in which a plurality of the required injection patterns are set, the apparatus performs required injection in which the execution timing of the final stage injection of the multistage injection is the closest to the compression top dead center among the required injection patterns. A fuel injection control device for an internal combustion engine, wherein a pattern is selected and operation control of the in-cylinder injection valve is executed. The fuel injection control device for an internal combustion engine according to claim 2,
The device is
In the specific engine operation region, a first required injection pattern in which the execution timing of the last stage injection is the first time closest to the compression top dead center, and the execution timing of the last stage injection is the first time. A second required injection pattern that is a second time earlier is set,
In the specific engine operation region, when the engine is in an engine operation state in which the first request injection pattern can be selected, the first request injection pattern is selected, and in the engine operation state in which the first request injection pattern cannot be selected. A fuel injection control device for an internal combustion engine, wherein the second required injection pattern is selected at a certain time. The fuel injection control device for an internal combustion engine according to claim 2 or 3,
The device is
When there are a plurality of required injection patterns in which the execution timing of the final stage injection is closest to the compression top dead center, among the required injection patterns, the final stage injection is performed with respect to the total injection amount in one combustion cycle. 2. A fuel injection control apparatus for an internal combustion engine, wherein a required injection pattern having the largest proportion of injection amount is selected. The fuel injection control device for an internal combustion engine according to any one of claims 2 to 4,
The intake stroke and the compression stroke of the internal combustion engine are preliminarily divided into a plurality of periods,
The said apparatus determines the combination of the presence or absence of injection execution in the said several period by the said request | requirement injection pattern, The fuel injection control apparatus of the internal combustion engine characterized by the above-mentioned. The fuel injection control device for an internal combustion engine according to claim 5,
The fuel injection control device for an internal combustion engine according to claim 1, wherein the plurality of periods include four periods, ie, a first half of an intake stroke, a second half of the intake stroke, a first half of a compression stroke, and a second half of the compression stroke. The fuel injection control device for an internal combustion engine according to any one of claims 2 to 6,
The device is
A priority for the selection is set for each required injection pattern,
In the specific operation region, an internal combustion engine that preferentially selects a required injection pattern in which the execution timing of the final injection of the multi-stage injection is closest to the compression top dead center according to the priority. Fuel injection control device.