JP6201300B2 - Fuel injection control device for internal combustion engine and fuel injection control method for internal combustion engine - Google Patents

Description

  The present invention relates to fuel injection control of a so-called direct injection type internal combustion engine in which fuel is directly injected into a cylinder.

  As fuel injection control for an in-cylinder direct injection internal combustion engine, the number of fuel injections and the fuel injection pressure corresponding to the engine load and the engine speed are set in advance as a map, and the map is searched according to the operating state and executed. What to do is known.

  By the way, in the fuel injection control as described above, there may be a difference between the actual fuel injection pressure (actual fuel injection pressure) and the fuel injection pressure set value set by the map search in a transient state where the operation state changes. . In addition, the above-described divergence may be increased due to variations or deterioration in the fuel pressure holding performance of the fuel pump and the influence of fuel properties and fuel temperature.

  When the actual fuel injection pressure is higher than the fuel injection pressure set value, the air / fuel ratio becomes richer than the target air / fuel ratio when operated with the injection pulse width set according to the fuel injection pressure set value. For this reason, the injection pulse width is corrected to be small by the air-fuel ratio feedback control based on the detected value of the exhaust air-fuel ratio, and as a result, the actual injection pulse width becomes smaller than the minimum allowable pulse width, resulting in a large variation in the injection amount and the combustion. May become unstable.

  The minimum allowable pulse width is the lower limit fuel injection pulse width at which the injection amount variation is within the allowable range.

  On the other hand, when the actual fuel injection pressure is lower than the fuel injection pressure set value, the atomization of fuel spray and the degree of mixing may deteriorate, and the fuel efficiency and exhaust performance may deteriorate.

  In order to prevent the occurrence of the phenomenon caused by the difference between the actual fuel injection pressure and the fuel injection pressure set value as described above, in Patent Document 1, when the fuel injection pulse is less than the minimum allowable pulse width, the air-fuel ratio is reduced. The fuel injection pulse width is increased by enrichment. In Patent Document 2, when the fuel injection pulse falls below the minimum allowable pulse width, the fuel injection pulse width is increased, and the intake air amount is increased correspondingly. The ignition timing is retarded so as to cancel out the torque increase due to the increase in the intake air amount.

Japanese Patent Laid-Open No. 10-18890 JP 2001-323834 A

  However, when the air-fuel ratio is enriched as in Patent Document 1, smoke is generated and exhaust performance is deteriorated. Moreover, if the ignition timing is retarded as in Patent Document 2, the fuel efficiency is deteriorated because the thermal efficiency is lowered.

  Accordingly, an object of the present invention is to provide a control device that prevents combustion from becoming unstable and suppresses deterioration of exhaust performance even when there is a difference between the actual fuel injection pressure and the fuel injection pressure set value. And

A fuel injection control device for an internal combustion engine according to the present invention sets a target fuel injection pressure based on an in-cylinder direct injection type fuel injection valve capable of executing fuel injection a plurality of times in one cycle, and an engine operating state, Setting means is provided for setting the basic number of times of fuel injection in one cycle based on the fuel injection pressure. The setting means has a differential pressure between the target fuel injection pressure and the actual fuel injection pressure detected by the fuel injection pressure detecting means greater than a preset threshold, and the actual fuel injection pressure is lower than the target fuel injection pressure. If, instead of the basic injection times, the basic injection times from rather multi based on said actual fuel injection pressure, and fuel injection period per injection, to a proportional relationship to the injection quantity and injection pulse width limit The number of fuel injections is set so as to be equal to or longer than the minimum fuel injection period, which is the injection pulse width of the first. Further, the setting means, when the differential pressure is larger than the threshold value and the actual fuel injection pressure is higher than the target fuel injection pressure, instead of the basic injection number, based on the actual fuel injection pressure, Set a small number of fuel injections.

  According to the present invention, when the difference between the target fuel injection pressure and the actual fuel injection pressure is large, the number of fuel injections is set based on the actual fuel injection pressure. Thus, even when the difference between the target fuel injection pressure and the actual fuel injection pressure is large, a homogeneous air-fuel mixture is formed in the combustion chamber, and as a result, deterioration of exhaust performance can be suppressed.

FIG. 1 is a configuration diagram of a system according to the first embodiment. FIG. 2 is a flowchart showing a fuel injection control routine according to the first embodiment. FIG. 3 is a map used to calculate the set fuel pressure. FIG. 4 is a map used to calculate the number of injections. FIG. 5 is a diagram showing the relationship between the injection pulse width and the injection amount. FIG. 6 is a diagram showing the relationship between the injection pulse width and the injection amount variation. FIG. 7 is a graph showing the characteristics of the particulate discharge concentration. FIG. 8 is a timing chart when the control routine of FIG. 2 is executed. FIG. 9 is a flowchart showing a fuel injection control routine according to the second embodiment. FIG. 10 is a map used to calculate the set fuel pressure. FIG. 11 is a map used to calculate the number of injections. 12A is a diagram showing the injection pulse width before correction based on the actual fuel pressure, and FIG. 12B is a diagram showing the injection pulse width when corrected to three-stage injection, and FIG. These are figures which show the injection pulse width at the time of correct | amending to 4-stage injection. FIG. 13 is a timing chart when the control routine of FIG. 9 is executed. FIG. 14 is a diagram showing another example of a map used for calculating the number of injections.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a configuration diagram of a system including an in-cylinder direct injection spark ignition internal combustion engine (hereinafter simply referred to as “internal combustion engine 1”) 1 according to a first embodiment of the present invention. Although the internal combustion engine 1 has other cylinders, only one cylinder is shown here for simplicity.

  The internal combustion engine 1 includes a cylinder head 1A and a cylinder block 1B. A piston 10 is housed in a cylinder 11 provided in the cylinder block 1B so as to be able to reciprocate. A combustion chamber 14 is defined by the wall surface of the cylinder 11, the crown surface of the piston 10, and the lower surface of the cylinder head 1A.

  An intake passage 2 and an exhaust passage 3 are formed in the cylinder head 1A. Both the intake passage 2 and the exhaust passage 3 are open to the combustion chamber 14, and the respective openings are opened and closed by the intake valve 6 and the exhaust valve 7. The intake valve 6 and the exhaust valve 7 are driven by the intake camshaft 4 and the exhaust camshaft 5, respectively. The intake camshaft 4 includes a variable valve mechanism that can change the valve timing.

  Further, the ignition plug 8 and the fuel injection valve 9 are arranged on the cylinder head 1A so as to face the combustion chamber 14.

  A collector tank 13 is interposed in the intake passage 2, and a throttle valve 12 is disposed on the upstream side of the intake air flow of the collector tank 13.

  The controller 20 executes the throttle valve 12 opening control, the fuel injection control of the fuel injection valve 9, the fuel injection control such as the injection amount, and the ignition timing control of the spark plug 8.

  The controller 20 executes each control described above based on detection signals from the throttle opening sensor 21, the crank angle sensor 22, the fuel pressure sensor 23, and the like. The controller 20 includes a microcomputer that includes a central processing unit (CPU), a read-only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface). It is also possible to configure the controller 20 with a plurality of microcomputers.

  In the internal combustion engine 1 configured as described above, the controller 20 sets a target fuel injection amount according to an operating state such as the engine speed and the required load, and further injects the target fuel injection amount as will be described later. The number of injections, the injection pulse width of each injection, and the injection timing are set.

  The target fuel injection amount is a fuel injection amount for realizing a target air-fuel ratio, for example, a theoretical air-fuel ratio. Then, the controller 20 performs feedback control of the fuel injection amount using a detection value of an exhaust air / fuel ratio sensor (not shown) in order to realize the target air / fuel ratio.

  As a fuel injection control for an internal combustion engine, when performing homogeneous combustion, for the purpose of improving the uniformity of the air-fuel mixture in the cylinder, multi-stage injection is performed in which the target fuel injection amount per cycle is injected in multiple times. Are known. In the case of single stage injection, in order to increase the uniformity, it is desirable to increase the time during which the fuel is atomized and mixed with air, that is, the fuel is injected at a crank angle close to the intake top dead center. However, if the fuel is injected at a crank angle close to the intake top dead center, the time until spark ignition becomes longer, and the cooling effect due to the endothermic reaction when the fuel vaporizes decreases. That is, in the case of single-stage injection, the uniformity improvement effect and the cooling effect are in a trade-off relationship. In this regard, according to the multi-stage injection, by setting two of the plurality of fuel injection timings to a timing close to the intake top dead center and a timing close to the ignition timing, it is possible to achieve both improved uniformity and a cooling effect. It becomes possible.

  By the way, in a transient state where the operating state changes, there may be a difference between the actual fuel injection pressure (actual fuel injection pressure) and the fuel injection pressure set value set by the map search. In addition, the above-described divergence may be increased due to variations or deterioration in the fuel pressure holding performance of the fuel pump and the influence of fuel properties and fuel temperature.

  Therefore, the controller 20 performs the control described below so that an appropriate fuel injection amount is obtained even when a deviation between the actual fuel injection pressure and the target fuel injection pressure occurs.

  FIG. 2 is a flowchart showing a fuel injection control routine executed by the controller 20 in the first embodiment. This routine is repeatedly executed at short intervals of about 10 milliseconds, for example.

  In step S1000, the controller 20 detects the load and rotation speed of the internal combustion engine 1. The load is detected based on the detection value of the throttle opening sensor 21. For example, the larger the throttle opening, the higher the load, and the smaller the throttle opening, the lower the load. In place of the throttle opening sensor 21, an accelerator opening sensor may be used.

  The rotational speed is detected based on, for example, a detection value of the crank angle sensor 22.

  In step S1010, the controller 20 reads the required fuel injection amount. Here, for example, a fuel injection amount map having the engine load and the engine rotation speed as the vertical axis and the horizontal axis, respectively, is created in advance, and a map search is performed using the load and the rotation speed detected in step S1000.

  In step S1020, the controller 20 reads a fuel injection pressure (hereinafter referred to as a set fuel pressure) FP and an injection frequency NI. The set fuel pressure FP is set using, for example, a map as shown in FIG. In FIG. 3, the vertical axis represents the engine load, the horizontal axis represents the engine rotation speed, and the higher the engine load, the higher the fuel pressure is set. The number of injections NI is set using, for example, a map as shown in FIG. 4, the vertical axis represents the engine load and the horizontal axis represents the engine rotational speed, as in FIG. 3. In the region of low rotation and high load, the higher the engine load, the greater the number of injections. In, a small number of injections is set. The number of injections set in FIG. 4 is called the basic injection number. Here, the low rotation is a region that is approximately half or less of the upper limit of the rotational speed, and the high load is a region that is approximately half or more of the engine load upper limit. In addition, regarding the number of injections, for example, the region A in FIG. 4 is 5 times, the region B is 3 times, the region between the regions A and B is 4 times, and the other regions are 1 time. In this case, the maximum number of basic injections is five.

  In step S1030, the controller 20 calculates an injection pulse input value Ti based on the required injection amount, the number of injections NI, and the set fuel pressure FP.

  In step S1040, the controller 20 detects an actual fuel injection pressure (hereinafter referred to as an actual fuel pressure) FPa by the fuel pressure sensor 23.

  In step S1050, the controller 20 determines whether or not the actual fuel pressure FPa is higher than the set fuel pressure FP and the difference between the actual fuel pressure FPa and the set fuel pressure FP is equal to or greater than a preset threshold value. The threshold value is a value in which a decrease in combustion stability due to the difference between the actual fuel pressure FPa and the set fuel pressure FP described above and deterioration in fuel efficiency and exhaust performance are in an acceptable range, and for each vehicle model to which the present embodiment is applied, It is set in advance by experiment or the like.

  As a result of the determination, if the difference between the actual fuel pressure FPa and the set fuel pressure FP is greater than or equal to the threshold value, the process of step S1080 is executed. If the difference is smaller than the threshold value, the process of step S1060 is executed.

  In step S1060, the controller 20 calculates an injection pulse width Tia based on the actual fuel pressure FPa. That is, the injection pulse width Tia is calculated based on the required injection amount, the number of injections NI, and the injection pulse width Tia. Here, the injection number NI here has an upper limit of the maximum number of basic injections.

  In step S1070, the controller 20 determines whether or not the injection pulse width Tia is equal to or greater than the minimum allowable pulse width Timin. Here, the minimum allowable pulse width will be described.

  FIG. 5 is a diagram showing the relationship between the injection pulse width and the injection amount when the fuel pressure is constant, and FIG. 6 is a diagram showing the relationship between the injection pulse width and the injection amount variation when the fuel pressure is constant. As shown in FIG. 5, the injection pulse width and the injection amount are generally in a proportional relationship, but the proportional relationship is not established in a region where the injection pulse width is small. Moreover, as shown in FIG. 6, it has the characteristic that the injection amount variation increases as the injection pulse width decreases. Therefore, the lower limit injection pulse width that establishes a proportional relationship between the injection amount and the injection pulse width is defined as the minimum allowable pulse width Timin. Returning to the description of FIG.

  If the result of determination in step S1070 is that the injection pulse width Tia is greater than or equal to the minimum allowable pulse width Timini, the process of step S1070 is executed, and if the injection pulse width Tia is smaller than the minimum allowable pulse width Timin, the process of step S1090 is executed. .

  In step S1080, the controller 20 sets the injection number NI read in step S1020 as the target injection number NIt.

  In step S1090, the controller 20 sets the target number of injections NIt so that the injection pulse width Tia becomes the minimum allowable pulse width Timini. Specifically, the injection number NI read in step S1020 is corrected to decrease. That is, if the number of injections NI is decreased while the total fuel injection amount per cycle is kept constant, the injection pulse width per injection increases, so that the injection pulse width Tia becomes larger than the minimum allowable pulse width Timin. Reduce the number of injections NI.

  FIG. 7 is a diagram showing an example of the relationship between the fuel pressure and the number of injections and the exhaust particulate concentration. The broken line in the figure shows the case where the number of injections is NI1, the alternate long and short dash line shows the case of NI2 times, and the broken line shows the case of NI3 times. Here, NI1 <NI2 <NI3. In addition, the injection amount per injection shall be equal.

  For example, it is assumed that the set fuel pressure FP is P1 and the actual fuel pressure FPa is P3, and the difference between P1 and P3 exceeds the threshold value. The number of injections set according to the set fuel pressure P1 is NI2 times, and the number of injections set according to the actual fuel pressure FPa is NI1 times.

  As shown in FIG. 7, the exhaust particulate concentration increases as the number of injections increases at the same fuel pressure, and the fuel pressure decreases as the injection count increases at the same exhaust particulate concentration. If the fuel pressure divergence is large as in the transition from point A to point B, the exhaust particulate concentration is maintained even if the number of injections is reduced.

  In FIG. 7, the injection pulse width Tia corresponding to the actual fuel pressure FPa is calculated in the control routine of FIG. 2, and the injection number NI is corrected to decrease so that the injection pulse width Tia is larger than the allowable minimum pulse width in step S1090. This corresponds to the transition from point A to point B. Therefore, the exhaust particulate concentration does not change.

  FIG. 8 is a timing chart when the above-described control routine is executed when shifting from the region A to the region B in FIGS. 3 and 4. Here, the target air-fuel ratio is the stoichiometric air-fuel ratio over the entire region.

  First, the case where the control routine of this embodiment is not executed will be described.

  When the throttle opening decreases from TV1 to TV2 at the timing T1 during traveling in the region A, the set fuel pressure FP decreases stepwise from FP1 to FP2. On the other hand, the actual fuel pressure FPa gradually decreases. Further, since the set fuel pressure FP changes at the timing T1, the number of injections NI decreases from NI1 to NI2.

  The injection pulse width Ti per injection also changes according to changes in the required injection amount, the set fuel pressure FP, and the number of injections. At this time, since the change in the actual fuel pressure FPa is delayed with respect to the change in the set fuel pressure FP, the actual fuel pressure FPa is higher than the set fuel pressure FP. Therefore, when fuel is injected with the injection pulse width calculated based on the set fuel pressure FP, the air-fuel ratio of the exhaust becomes richer than the stoichiometric air-fuel ratio, and the injection pulse width Ti is corrected to decrease by the air-fuel ratio feedback control, so that the injection pulse width is Ti2. It becomes. Here, it is assumed that the ejection pulse width Ti2 is equal to or smaller than the allowable minimum pulse width.

  After timing T1, due to the decrease in the actual fuel pressure FPa and the decrease in the engine speed, the injection pulse width gradually increases from Ti2, becomes larger than the allowable minimum pulse width, and eventually converges to the injection pulse width Ti3 corresponding to the set fuel pressure FP. To do. In practice, it takes time for the pulse width to change by air-fuel ratio feedback control, but for simplicity, in FIG. 8, the pulse width Ti2 after correction by feedback control is set at timing T1.

  Next, the case where the control routine of this embodiment is performed is demonstrated.

  At timing T1, since the difference between the actual fuel pressure FPa and the set fuel pressure FP is equal to or greater than the threshold value, the injection pulse width corresponding to the actual fuel pressure FPa is set. Here, it is assumed that the injection pulse width based on the actual fuel pressure FPa is smaller than the allowable minimum pulse width. Therefore, in order to increase the injection pulse width per one time, the injection number NI is corrected to decrease. Specifically, the number of injections is corrected from NI2 to NI3, and as a result, the injection pulse width per time becomes larger than the allowable minimum pulse width.

  After timing T1, the same control is performed until timing T2 when the difference between the actual fuel pressure FPa and the set fuel pressure FP matches the threshold, and the number of injections is NI3. However, since the actual fuel pressure FPa decreases while the number of injections is NI3, the injection pulse width gradually increases.

  When the timing T2 is exceeded, the control by the injection pulse width corresponding to the actual fuel pressure FPa is returned to the control by the injection pulse width corresponding to the set fuel pressure FP. As a result, the injection number NI changes from NI3 to NI2.

  As described above, when the difference between the set fuel pressure FP and the actual fuel pressure FPa is large, the number of injections is set based on the actual fuel pressure FPa, so the number of injections is set so that the injection pulse width is equal to or greater than the allowable minimum pulse width Timin. It is possible to reduce the variation in the injection amount and keep it below the allowable value. As a result, stable operation of the engine can be maintained.

  Further, since the difference between the actual fuel pressure FPa and the set fuel pressure FP is equal to or greater than the threshold value, the exhaust performance can be maintained without increasing the exhaust particulate concentration even if the number of injections is reduced.

  As described above, according to the present embodiment, the following effects can be obtained.

  When the differential pressure between the target fuel injection pressure (set fuel pressure FP) and the actual fuel injection pressure (actual fuel pressure FPa) is larger than a preset threshold, the setting means (controller 20) The number of fuel injections is set based on the actual fuel pressure FPa. Thereby, even when the difference between the set fuel pressure FP and the actual fuel pressure FPa is large, a homogeneous air-fuel mixture can be formed in the combustion chamber, and as a result, deterioration of exhaust performance can be suppressed.

  Further, when the controller 20 sets the number of fuel injections based on the actual fuel pressure FPa, the fuel injection period per injection is equal to or longer than the minimum fuel injection period (allowable minimum pulse width) determined from the injection characteristics of the fuel injection valve 9. The number of injections is set so that As a result, stable fuel supply can be realized, and engine torque, combustion stability, and exhaust performance can be maintained.

  Further, when the differential pressure between the set fuel pressure FP and the actual fuel pressure FPa is equal to or greater than the threshold value and the actual fuel pressure FPa is higher than the set fuel pressure FP, the controller 20 sets the number of injections less than the basic number of injections. Since fuel atomization and vaporization are promoted by the amount of fuel pressure and mixing can be improved, deterioration of fuel efficiency and exhaust performance can be suppressed even if the number of injections is set to be small.

  In addition, the effect by this embodiment becomes larger when using the fuel whose calorific value per unit weight is low compared with gasoline like alcohol containing fuel, such as ethanol, for example. This is because the amount of heat generated per unit amount is low, so the injection amount increases and the influence of fuel pressure increases.

(Second Embodiment)
In the second embodiment, the configuration of the system is the same as that of the first embodiment, but the change direction of the operation region is opposite to that of the first embodiment, that is, the region B changes to the region A as shown in FIGS. It is related to the control.

  FIG. 9 is a flowchart showing a fuel injection control routine executed by the controller 20 in the second embodiment. This routine is repeatedly executed at short intervals of about 10 milliseconds, for example.

  Steps S2000-S2040 are the same as steps S1000-S1040 in FIG.

  In step S2050, the controller 20 determines whether or not the actual fuel pressure FPa is smaller than the set fuel pressure FP and the difference between the actual fuel pressure FPa and the set fuel pressure FP is equal to or greater than a preset threshold value. The threshold is set based on the same concept as the threshold in step S1050 in FIG. As a result of the determination, if the difference between the set fuel pressure FP and the actual fuel pressure FPa is greater than or equal to the threshold value, the process of step S2060 is executed. Otherwise, the number of injections is set to NI in step S2080 as in step S1080 of FIG. .

  In step S2060, the controller 20 calculates the injection pulse width Tia based on the actual fuel pressure FPa as in step S1060 of FIG.

  In step S2070, the controller 20 increases and corrects the injection number NI as described below.

  First, it is confirmed whether or not the injection pulse width Tia calculated in step S2060 is greater than or equal to the allowable minimum pulse width Timin. If it is equal to or greater than the allowable minimum pulse width Timin, the injection pulse width Tia is recalculated by increasing the injection frequency by one from the injection frequency NI read in step S2020. If the recalculated injection pulse width Tia is equal to or greater than the allowable minimum pulse width Timin, the number of injections NI is further increased by 1, and the injection pulse width Tia is recalculated. By repeating this, the maximum number of injections is calculated in a range where the injection pulse width Tia is equal to or greater than the allowable minimum pulse width Timin, and this maximum number of injections is set as the injection number NIt.

  When increasing the number of injections, the injection pulse width of each time is made equal. For example, consider a case where before the increase correction, as shown in FIG. 12A, two-stage injection is performed, and the main injection has a longer injection pulse width than after-injection. In this case, as shown in FIG. 12 (B) when changing to the three-stage injection by the increase correction, and as shown in FIG. 12 (C) when changing to the four-stage injection, the injection pulse width of each injection. Evenly.

  In addition, when the number of injections is set based on the actual fuel pressure FPa and the multistage injection is performed, the injection is performed at least once at the time when the homogeneous mixture is formed in the combustion chamber. This is because the internal combustion engine 1 executes the control of the present embodiment in the homogeneous combustion region that occupies most of the operating region, thereby improving the fuel efficiency.

  By making the injection pulse widths uniform in this way, it is possible to set a larger number of injections under the condition that the total injection amount per cycle is determined. As a result, the homogeneity of the air-fuel mixture Can be increased.

  FIG. 13 is a timing chart when the above-described control routine is executed when shifting from region B to region A in FIGS. 10 and 11. Here, the target air-fuel ratio is the stoichiometric air-fuel ratio over the entire region.

  First, the case where the control routine of this embodiment is not executed will be described.

  When the throttle opening increases from TV2 to TV1 at the timing T1 during traveling in the region B, the set fuel pressure FP increases stepwise from FP2 to FP1. On the other hand, the actual fuel pressure FPa gradually increases. Further, since the set fuel pressure FP changes at the timing T1, the number of injections NI increases from NI3 to NI2.

  The injection pulse width Ti per injection also changes according to changes in the required injection amount, the set fuel pressure FP, and the number of injections. At this time, since the change in the actual fuel pressure FPa is delayed with respect to the change in the set fuel pressure FP, the actual fuel pressure FPa is lower than the set fuel pressure FP. Therefore, when fuel is injected with the injection pulse width calculated based on the set fuel pressure FP, the air-fuel ratio of the exhaust gas becomes leaner than the stoichiometric air-fuel ratio, and the injection pulse width Ti is increased and corrected by the air-fuel ratio feedback control, so that the injection pulse width is Ti1. It becomes.

  After timing T1, the injection pulse width gradually decreases from Ti1 due to the increase in the actual fuel pressure FPa and the increase in the engine speed, and eventually converges to the injection pulse width Ti3 corresponding to the set fuel pressure FP. In practice, it takes time for the pulse width to change by air-fuel ratio feedback control, but for simplicity, in FIG. 13, the pulse width Ti2 after correction by feedback control is set at timing T1.

  Next, the case where the control routine of this embodiment is performed is demonstrated.

  At timing T1, since the difference between the actual fuel pressure FPa and the set fuel pressure FP is equal to or greater than the threshold value, the injection pulse width corresponding to the actual fuel pressure FPa is set. At this time, it is assumed that the number of injections can be increased while satisfying the condition that the injection pulse width is equal to or greater than the allowable minimum pulse width Timin. Therefore, the number of injections is corrected to increase to NI1.

  After timing T1, the same control is performed until timing T2 when the difference between the actual fuel pressure FPa and the set fuel pressure FP matches the threshold, and the number of injections is NI1. However, since the actual fuel pressure FPa decreases while the number of injections is NI1, the injection pulse width gradually decreases.

  When the timing T2 is exceeded, the control by the injection pulse width corresponding to the actual fuel pressure FPa is returned to the control by the injection pulse width Ti corresponding to the set fuel pressure FP. As a result, the injection number NI changes from NI1 to NI2.

  As described above, when the difference between the set fuel pressure FP and the actual fuel pressure FPa is large, the injection pulse width is set based on the actual fuel pressure FPa, and the number of injections is set within a range where the injection pulse width is equal to or greater than the allowable minimum pulse width Timin. Increase correction. By increasing the number of injections in this way, the homogeneity of the fuel spray increases, and as a result, deterioration of fuel consumption performance and exhaust performance can be suppressed.

  In the present embodiment, the case where the multistage injection is basically performed as shown in FIG. 11 has been described. However, the present invention is not limited to this. For example, as shown in FIG. In the case of performing single-stage injection, the control of this embodiment can be similarly applied.

  As described above, according to this embodiment, in addition to the same effects as those of the first embodiment, the following effects can be further obtained.

  When the differential pressure between the set value FP and the actual fuel pressure FPa is equal to or greater than the threshold value and the actual fuel pressure FPa is lower than the set fuel pressure FP, the controller 20 sets the number of injections greater than the basic number of injections. Since the homogenization of the air-fuel mixture is promoted by increasing the number of injections, it is possible to compensate for poor mixing due to a decrease in fuel pressure, and as a result, it is possible to suppress deterioration in fuel efficiency and exhaust performance.

  Since the controller 20 sets the number of injections with the maximum number of basic injections as an upper limit, the control becomes easy. Moreover, since the increase amount of the total number of injections can be suppressed by setting the upper limit of the number of injections as described above, deterioration of the fuel injection valve 9 over time can be suppressed.

  The controller 20 sets the fuel injection period of each fuel injection equally when setting the number of times of fuel injection, so that the number of injections can be increased, and as a result, the homogenization of the air-fuel mixture is promoted. The effect of etc. becomes larger.

  When setting the number of injections based on the actual fuel pressure FPa, the controller 20 sets the fuel injection timing of at least one fuel injection to a timing when a homogeneous mixture is formed in the combustion chamber. Since the homogeneous operation region occupies most of the engine operation region, this can improve fuel efficiency.

  The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims.

1 In-cylinder direct injection spark ignition internal combustion engine (internal combustion engine)
2 intake passage 3 exhaust passage 4 intake camshaft 5 exhaust camshaft 6 intake valve 7 exhaust valve 8 spark plug 9 fuel injection valve 10 piston 11 cylinder 12 throttle valve 13 collector tank 14 combustion chamber 20 controller (setting means)
21 Throttle opening sensor 22 Crank angle sensor 23 Fuel pressure sensor (fuel injection pressure detection means)

Claims (8)

An in-cylinder direct injection type fuel injection valve capable of performing fuel injection a plurality of times during one cycle;
Setting means for setting a target fuel injection pressure based on the engine operating state, and setting a basic injection number which is the number of fuel injections in one cycle according to the target fuel injection pressure based on the engine operating state;
Fuel injection pressure detection means for detecting the actual fuel injection pressure;
In a fuel injection control device for an internal combustion engine comprising:
The setting means is such that a differential pressure between the target fuel injection pressure and the actual fuel injection pressure detected by the fuel injection pressure detecting means is not less than a preset threshold value, and the actual fuel injection pressure is the target fuel. is lower than the injection pressure, instead of the basic injection times, wherein on the basis of the actual fuel injection pressure basic injection times from rather large, and the fuel injection period per injection, the injection quantity and injection pulse width A fuel injection control device for an internal combustion engine that sets the number of fuel injections so as to be equal to or longer than a minimum fuel injection period, which is a lower limit injection pulse width that establishes a proportional relationship . The fuel injection control device for an internal combustion engine according to claim 1 ,
The fuel injection control device for an internal combustion engine, wherein the setting means sets the number of injections with the maximum number of basic injections as an upper limit. An in-cylinder direct injection type fuel injection valve capable of performing fuel injection a plurality of times during one cycle;
Setting means for setting a target fuel injection pressure based on the engine operating state, and setting a basic injection number which is the number of fuel injections in one cycle according to the target fuel injection pressure based on the engine operating state;
Fuel injection pressure detection means for detecting the actual fuel injection pressure;
In a fuel injection control device for an internal combustion engine comprising:
The setting means is such that a differential pressure between the target fuel injection pressure and the actual fuel injection pressure detected by the fuel injection pressure detecting means is not less than a preset threshold value, and the actual fuel injection pressure is the target fuel. A fuel injection control device for an internal combustion engine that sets a fuel injection frequency smaller than the basic injection frequency based on the actual fuel injection pressure instead of the basic injection frequency when the injection pressure is higher. The fuel injection control device for an internal combustion engine according to claim 3 ,
The setting means is a fuel injection control device for an internal combustion engine that sets the fuel injection period of each fuel injection equally when setting the number of times of fuel injection a plurality of times. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 4 ,
When the number of injections is set based on the actual fuel injection pressure, the setting means uniformly mixes the fuel injection timing of at least one fuel injection into the combustion chamber during the intake stroke or the compression stroke. A fuel injection control device for an internal combustion engine, which is set at a time when a gas is formed. The fuel injection control device for an internal combustion engine according to any one of claims 1 to 5 ,
A fuel injection control device for an internal combustion engine in which the fuel used is an alcohol-containing fuel. In a fuel injection control method for an internal combustion engine comprising an in-cylinder direct injection fuel injection valve capable of performing fuel injection a plurality of times during one cycle,
Setting a target fuel injection pressure based on engine operating conditions;
Setting a basic injection number that is the number of fuel injections in one cycle according to the target fuel injection pressure based on the engine operating state;
Detecting the actual fuel injection pressure;
Comparing a differential pressure between the target fuel injection pressure and the actual fuel injection pressure detected by the fuel injection pressure detecting means with a preset threshold value;
When the differential pressure is greater than the threshold value and the actual fuel injection pressure is lower than the target fuel injection pressure, instead of the basic injection number, based on the actual fuel injection pressure, the basic injection number A step of setting the number of times of fuel injection so that the fuel injection period per injection is greater than or equal to a minimum fuel injection period that is a lower limit injection pulse width that establishes a proportional relationship between the injection amount and the injection pulse width ;
A fuel injection control method for an internal combustion engine. In a fuel injection control method for an internal combustion engine comprising an in-cylinder direct injection fuel injection valve capable of performing fuel injection a plurality of times during one cycle,
Setting a target fuel injection pressure based on engine operating conditions;
Setting a basic injection number that is the number of fuel injections in one cycle according to the target fuel injection pressure based on the engine operating state;
Detecting the actual fuel injection pressure;
Comparing a differential pressure between the target fuel injection pressure and the actual fuel injection pressure detected by the fuel injection pressure detecting means with a preset threshold value;
When the differential pressure is larger than the threshold value and the actual fuel injection pressure is higher than the target fuel injection pressure, instead of the basic injection number, the basic injection number is based on the actual fuel injection pressure. Setting a small number of fuel injections;
A fuel injection control method for an internal combustion engine.

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