JP2007040128A - Fuel injection control device for direct injection internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection control device for a direct injection internal combustion engine, capable of effectively suppressing lowering in combustion efficiency accompanying the secular deterioration on the injection characteristics of an injector. <P>SOLUTION: An electronic control device corrects a fuel injection command value according to the secular deterioration on the injection characteristics of the injector for injecting fuel during compression stroke. Accompanying an increase in the degree of secular deterioration, the electronic control device corrects the fuel injection command value to advance driving current rise completion timing for opening the injector. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel injection control device for a direct injection internal combustion engine provided with correction means for correcting a fuel injection command value in accordance with deterioration with time of injection characteristics of an injector.

  Conventionally, a direct injection internal combustion engine in which fuel is directly injected into a cylinder using an injector is known. In a direct injection internal combustion engine, for example, the amount of fuel in a cylinder can be controlled more precisely than in an internal combustion engine in which fuel is injected into an intake pipe, and fuel efficiency and exhaust performance can be further improved. .

  However, in such a direct injection internal combustion engine, for example, when the slidability of the needle valve built in the injector is deteriorated or the contact portion between the valve and the seat is worn away, There is a concern that the accuracy of fuel injection control may be reduced, such as a difference between the required amount of fuel and the actual injection amount due to a change in the operating state. Such a decrease in accuracy leads to a decrease in combustion efficiency, which in turn causes an increase in noise, a deterioration in exhaust performance, a decrease in engine output, and the like.

For example, in the fuel injection control device for a direct injection internal combustion engine described in Patent Document 1, when the deterioration with time of the injection characteristics of the injector occurs, the fuel injection period is extended to extend the fuel injection amount due to the deterioration with time. Can be avoided.
JP 2002-89333 A

  However, when the injector is deteriorated, the fuel at the initial stage of the fuel injection period, for example, the valve opening start timing (needle valve lift start timing) is delayed or the increase rate of the valve opening is decreased. A decrease in the injection rate, that is, a delay in the increase in the fuel injection rate is likely to occur. The delay in the increase in the fuel injection rate is a cause of occurrence of a phenomenon that has a particularly great influence on the combustion state, such as fuel shortage in the cylinder and fuel atomization at the start of combustion. In the aspect in which the fuel is injected during the compression stroke, for example, the period from the fuel injection start time to the combustion start time is short compared with the aspect in which the fuel is injected during the intake stroke. There is a concern that the influence of the delay tends to be particularly large, and the above-described increase in noise, deterioration in exhaust performance, reduction in engine output, and the like become particularly significant. In particular, in a diesel internal combustion engine that self-ignites the fuel, the delay in ignition and the state of premixed combustion are greatly affected by the delay in increase in the fuel injection rate.

  As described above, in the control device described in Patent Document 1, the fuel injection period is extended when the injector deteriorates with time, but the increase in the fuel injection rate, which is a malfunction in the initial stage of the fuel injection period, is addressed. It was not possible to do so, leaving room for improvement.

  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 a direct injection internal combustion engine that can effectively suppress a decrease in combustion efficiency associated with deterioration over time in the injection characteristics of the injector. Is to provide.

In the following, means for achieving the above object and its effects are described.
First, the invention according to claim 1 is a fuel injection control device for a direct injection internal combustion engine provided with a correction means for correcting a fuel injection command value in accordance with deterioration with time of an injection characteristic of an injector that injects fuel during a compression stroke. The correction means corrects the fuel injection command value so that the rise completion timing of the drive current for opening the injector is advanced as the degree of deterioration with time increases. To do.

  According to this configuration, the valve opening degree of the injector is increased earlier by advancement of the rising completion timing of the drive current. According to this, it becomes possible to supply more fuel into the cylinder by the start of combustion, and further, it becomes possible to promote atomization of fuel at the start of combustion, and so on. Can be effectively suppressed. As a result, increase in noise, deterioration in exhaust performance, reduction in engine output, and the like are effectively suppressed.

The “fuel injection command value” is a command value related to the fuel injection mode, and means a command value related to the fuel injection amount and the fuel injection timing, for example.
The gist of the invention of claim 2 is that, in the invention of claim 1, the correction means advances the rise start timing of the drive current to advance the rise completion timing of the drive current.

  According to this configuration, since the rising start timing of the drive current of the injector is advanced, the rising completion timing is advanced by that amount. Therefore, as a result of the valve opening of the injector becoming larger earlier, an increase delay in the fuel injection rate accompanying the deterioration of the injector is suppressed.

  The gist of the invention described in claim 3 is that, in the invention described in claim 1 or 2, the correction means increases the rising speed of the driving current to advance the rising completion timing of the driving current.

  According to this configuration, the rise speed of the drive current of the injector is increased, so that the period from the rise start time to the rise completion time can be shortened. Therefore, the valve opening of the injector can be increased earlier by that amount, and an increase delay in the fuel injection rate due to the deterioration with time can be suppressed.

  Here, if there is an increase delay in the fuel injection rate as described above, the fuel injection period will be shortened by the delay if the correction is not applied to the drive current energization period. There is a concern that the injection amount will decrease. In that respect, according to a fourth aspect of the present invention, when the correction means advances the rising completion timing of the driving current, it extends the energizing period of the driving current, thereby adopting a configuration in which the energizing period is increased. Through this extension, reduction of the fuel injection rate can be suppressed. Accordingly, not only the initial stage of fuel injection but also a decrease in the fuel injection rate is suppressed over a wide range of the fuel injection period, and a decrease in combustion efficiency is effectively suppressed. As a result, an increase in noise, a deterioration in exhaust performance, a decrease in engine output, and the like are further suppressed.

  According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, when the internal combustion engine is in a steady operation state, the fuel injection command value is feedback controlled so as to maintain the steady operation state. And a determination means for determining that the degree of deterioration with time has increased when the fuel injection command value feedback-controlled by the maintenance control means has shifted to the side where the fuel injection amount increases. Is the gist.

  When the degree of deterioration of the injection characteristics in the injector increases, the actual fuel injection amount for the same fuel injection command value decreases accordingly. Therefore, when the fuel injection command value is feedback controlled so that the actual fuel injection amount matches the required fuel injection amount, such a decrease in the actual fuel injection amount, that is, a shortage of the actual fuel injection amount with respect to the required fuel injection amount. In order to avoid this, the fuel injection command value is changed and adjusted to a value for injecting a larger amount of fuel. Therefore, according to the present invention, the degree of deterioration over time of the injection characteristics of the injector can be suitably grasped based on the transition of the fuel injection command value that is feedback-controlled to maintain the steady operation state.

  The correction relating to the fuel injection command value described above can be suitably applied to a diesel internal combustion engine as in the sixth aspect of the invention. Diesel internal combustion engines self-ignite fuel by the temperature rise of the air-fuel mixture in the compression stroke. For example, the amount of fuel in a cylinder in the compression stroke is different from that of an internal combustion engine using a spark plug such as a gasoline internal combustion engine. The combustion start timing and combustion state tend to be greatly influenced by the atomization state. That is, in the diesel internal combustion engine, the effect obtained by the invention according to any one of claims 1 to 5 is particularly useful.

DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment in which the present invention is applied to a fuel injection device for an on-vehicle direct injection diesel internal combustion engine will be described with reference to FIGS.
As shown in FIG. 1, a direct injection diesel internal combustion engine 11 includes a cylinder head 12 and a cylinder block 14 in which a plurality of cylinders 13 are formed. A piston 15 is accommodated in each cylinder 13 so as to be able to reciprocate. Each piston 15 is connected via a connecting rod 16 to a crankshaft (not shown) that is an output shaft of the internal combustion engine 11. The reciprocating motion of each piston 15 is converted into rotational motion by the connecting rod 16 and then transmitted to the crankshaft.

  An intake passage 18 and an exhaust passage 19 are connected to each cylinder 13, and the connection portion between the intake / exhaust passages 18 and 19 and the cylinder 13 is opened and closed in conjunction with the rotation of the crankshaft. An intake valve 21 and an exhaust valve 22 are provided.

  The cylinder head 12 is provided with injectors (fuel injection valves) 23 that directly inject fuel into each cylinder 13. Fuel injection from each injector 23 to the corresponding cylinder 13 is controlled by an electromagnetic valve 23e. The injector 23 is connected to the common rail 25, and while the electromagnetic valve 23e is open, the fuel in the common rail 25 is injected from the injector 23 into the corresponding cylinder 13.

  In the present embodiment, fuel is injected and supplied from the injector 23 to the cylinder 13 in the compression stroke. As the pressure and temperature in the cylinder 13 rise, the fuel self-ignites and burns. The piston 15 is reciprocated by the combustion gas generated at this time, the crankshaft is rotated, and the driving force (output torque) of the internal combustion engine 11 is obtained. The combustion gas is discharged to the outside of the internal combustion engine 11 through the exhaust passage 19.

  A relatively high pressure fuel corresponding to the fuel injection pressure is accumulated in the common rail 25. The common rail 25 is supplied with high-pressure fuel sucked and boosted from the fuel tank 29 by the supply pump 27. As the supply pump 27, a known discharge capacity variable type high pressure pump is used. The amount of fuel supplied from the supply pump 27 to the common rail 25 is controlled by adjusting the opening of an electromagnetic throttle valve 31 provided in the pump 27. The amount of fuel that is not supplied to the common rail 25 by this opening degree adjustment is returned to the fuel tank 29 without being pressurized.

  Further, the common rail 25 is provided with an electromagnetic pressure reducing valve 33 capable of reducing its internal pressure (fuel injection pressure). When the common rail 25 is depressurized, the fuel of the common rail 25 is returned to the fuel tank 29 via the electromagnetic pressure reducing valve 33.

  In the present embodiment, various sensors such as a water temperature sensor 41, a rotation speed sensor 42, an accelerator sensor 43, and a fuel pressure sensor 44 are used to detect the operating state of the internal combustion engine 11. The water temperature sensor 41 is attached to the cylinder block 14 and detects the cooling water temperature that is the temperature of the cooling water flowing in the water jacket 14a. The rotational speed sensor 42 is disposed in the vicinity of the crankshaft and detects the rotational speed (engine rotational speed) of the internal combustion engine 11 that is the rotational speed of the crankshaft per unit time. The accelerator sensor 43 detects the accelerator opening that is the amount of depression of the accelerator pedal 39 by the driver. The fuel pressure sensor 44 is attached to the common rail 25 and detects the internal pressure of the common rail 25, that is, the fuel injection pressure.

  The vehicle is provided with an electronic control unit (ECU) 51 that controls each part of the internal combustion engine 11 based on detection values of various sensors 41 to 44. The electronic control unit 51 is configured around a microcomputer, and a central processing unit (CPU) performs arithmetic processing according to a control program, initial data, control map, etc. stored in a read-only memory (ROM). Various controls are executed based on the calculation result. The calculation result by the CPU is temporarily stored in a random access memory (RAM).

  The electronic control unit 51 calculates the fuel injection amount and the fuel injection timing according to the operating conditions of the internal combustion engine 11. Then, a fuel injection period corresponding to the calculated fuel injection amount is calculated according to the engine speed and fuel injection pressure at that time. The command value (fuel injection command value) regarding the fuel injection amount and fuel injection timing calculated in this way is output to the injector drive circuit (EDU) 53, and a drive current corresponding to the command value is output from the drive circuit 53 to the electromagnetic valve 23e. Is output, the injector 23 is driven. As a result, the electromagnetic valve 23e is kept open for the fuel injection period after being opened at the fuel injection timing. By the operation of the electromagnetic valve 23e, high-pressure fuel from the common rail 25 is injected into each cylinder 13 through the injector 23.

  The electronic control unit 51 is configured to maintain the engine rotation speed at a predetermined rotation speed (idle rotation speed) during the idling operation of the internal combustion engine 11 based on the detected value of the rotation speed sensor 42. Idle speed control (ISC) is executed to feedback control the value. As a result, even if various changes with time occur in the internal combustion engine 11, an amount of fuel suitable for maintaining the idle rotation speed can be injected.

  By the way, in the present embodiment, in the fuel injection control as described above, the fuel injection command value is corrected according to the deterioration over time related to the injection characteristics of the injector 23. This is intended to avoid such an inconvenience because a difference occurs in the fuel injection amount with respect to the same fuel injection command value when the injection characteristic of the injector 23 changes due to deterioration with time.

  Such deterioration with time occurs, for example, as follows. That is, as shown in FIG. 2, the needle valve 23 b is accommodated in the housing 23 a of the injector 23. Incidentally, the left side of the imaginary straight line (one-dot chain line) L in the figure shows the state before the deterioration with time, and the right side shows the state after the deterioration with time.

  A plurality of injection ports 23c for injecting internal fuel into the cylinder 13 are formed at the tip (lower end) side portion of the housing 23a. The fuel injection between the injection port 23c and the common rail 25 is executed / stopped by communication / blocking by the separation / contact between the needle valve 23b and the seat 23d. That is, the needle valve 23b and the seat 23d are repeatedly contacted and separated by repeated fuel injection.

  The injector 23 is configured such that the needle valve 23b and the seat 23d are in line contact at the part A as shown in the left part of the figure. As the injector 23 is used for a long time, the contact portion between the needle valve 23b and the seat 23d is abraded due to the repeated contact and separation, and the needle valve 23b and the seat 23d are shown in the right portion of FIG. Are in surface contact with each other, and the needle valve 23b is displaced toward the tip side from the beginning of manufacture. As a result, when the electromagnetic valve 23e is opened to inject fuel, the lift of the needle valve 23b is delayed, and the start of fuel injection is delayed. In addition, when the area where the fuel pressure applied to the lift of the needle valve 23b acts on the valve 23b (the pressure receiving area of the needle valve 23b) changes due to the wear, the increase rate of the lift amount also decreases. Such a delay in the start of fuel injection and a decrease in the rate of increase in the lift amount, that is, a delay in the increase in the fuel injection rate cause the fuel injection amount to be insufficient.

  For example, in the ISC, feedback control of the fuel injection amount is performed based on the detected value of the rotational speed sensor 42 so that the idle rotational speed does not decrease due to the shortage of the fuel injection amount accompanying such deterioration over time. . Therefore, as the degree of deterioration with time increases, the fuel injection command value during idle operation is corrected to the side where the fuel injection amount increases in order to keep the idle rotation speed constant.

  FIG. 3 shows an example of the relationship between the total travel distance from when the vehicle is new (immediately after the line is turned off) and the fuel injection command value (in this case, the command value related to the fuel injection amount) during idle operation controlled by ISC. Indicates. Hereinafter, the command value of the fuel injection amount based on this ISC is referred to as “idle injection amount command value”.

  Here, the idle injection amount command under the same engine operating conditions, for example, that the warm-up operation has been completed, or that an external load from the compressor of the air conditioner is not acting on the internal combustion engine 11 or the like. The transition of values is shown.

  As shown in FIG. 3, since the friction loss in the movable part of the internal combustion engine 11 is large between the total travel distance M0 and the total travel distance M1 when the vehicle is new, a decrease in the idle rotation speed due to such a load. In order to suppress this, the idle injection amount command value is set to be larger than the minimum value S1. As the total travel distance approaches from the distance M0 to the distance M1, the friction loss decreases, and as a result, the idle injection amount command value gradually decreases. The period from the total traveling distance from this distance M0 to the distance M1 corresponds to a so-called “break-in period”. After the running-in period is over, the idle injection amount command value is continuously stabilized at the minimum value S1.

  From the time when the total travel distance reaches the distance M2, the influence of the deterioration with time of the injector 23 occurs and the degree gradually increases. That is, the idle injection amount command value gradually increases from the minimum value S1 with the increase in the degree of deterioration over time in order to suppress the decrease in the actual fuel injection amount due to the deterioration over time (the decrease in the idle rotation speed associated therewith). The direction is corrected. Therefore, here, the idle injection amount command value after the end of the break-in period, that is, after the time when the total traveling distance becomes the distance M1, reflects the degree of deterioration with time.

  Therefore, the electronic control unit 51 grasps the degree of deterioration with time based on the transition of the idle injection amount command value under the same engine operating condition. More specifically, for example, the minimum value S1, which is a stable idle injection amount command value after the end of the break-in period, is stored as a reference value, and the subsequent idle injection amount command value is increased from this reference value. Ascertain the degree of deterioration with time.

  Thus, during idle operation, compensation of such fuel injection amount by ISC is achieved. However, if the internal combustion engine 11 is driven without such compensation of the fuel injection amount other than during idle operation, such as when the vehicle is running, the actual fuel injection amount is not in a desired state. The engine will be operated.

  Therefore, in the present embodiment, the fuel injection amount is compensated at a time other than the idling operation according to the degree of deterioration with time of the injector 23 as grasped based on the transition of the idle injection amount command value as described above. Yes. Specifically, for example, the fuel injection amount is further increased by extending the fuel injection period, that is, delaying the completion timing of the fuel injection in the injector 23, thereby suppressing the decrease in the actual fuel injection amount due to the deterioration with time. I am doing so.

  Here, transition of the fuel injection rate and the cylinder internal pressure will be described with reference to FIG. In the present embodiment, fuel injection is started during the compression stroke (first crank angle CA1). Then, the fuel injection rate increases, and combustion (premixed combustion) starts when the fuel self-ignites immediately before TDC (second crank angle CA2). As a result, the cylinder internal pressure rapidly increases. At approximately the same time as TDC, combustion shifts to diffusion combustion (third crank angle CA3), and then the fuel injection rate decreases to “0” (fourth crank angle CA4) with the end of fuel injection.

  In the figure, the period from the first crank angle CA1 to the second crank angle CA2 corresponds to the ignition delay period T1, and the period from the second crank angle CA2 to the third crank angle CA3 is premixed. The period corresponding to the combustion period T2 and from the third crank angle CA3 to the fourth crank angle CA4 corresponds to the diffusion combustion period T3.

  Thus, in the internal combustion engine 11 in which the fuel injection is started during the compression stroke, the period from the time when the fuel injection is started to the fuel ignition is longer than the mode in which the fuel injection is started during the intake stroke. In short, the fuel injection start timing and the fuel injection rate immediately after the start greatly affect the combustion state. That is, when the fuel injection start timing or the fuel injection rate immediately after the start deviates from the desired one, problems such as an increase in noise, a deterioration in exhaust performance, a decrease in engine output, and the like become more serious. There is concern.

  As described above, in the present embodiment, the fuel injection period is extended in accordance with the above-described deterioration of the injector 23. However, the fuel injection accompanying the above-described deterioration with time is only required to correct the fuel injection command value. I cannot cope with the delay in the rate increase.

  Therefore, in the present embodiment, the fuel injection command value applied in the initial stage of fuel injection is corrected according to the degree of deterioration with time of the injector 23. Hereinafter, the aspect of the fuel injection command value correction process will be described with reference to FIGS. 5 and 6.

  As shown in FIG. 5, the electronic control unit 51 determines the degree of deterioration with time of the injector 23 based on the transition of the idle injection amount command value calculated as described above by the ISC (step S110). At this time, the electronic control unit 51 determines that the degree of deterioration with time is larger as the idle injection amount command value is larger than the minimum value S1.

  Then, the electronic control device 51 outputs the fuel injection command value corrected so that the rising start timing of the drive current of the solenoid valve 23e is advanced according to the degree of deterioration with time to the injector drive circuit 53 (step) S120). At this time, the electronic control unit 51 corrects the fuel injection command value so that the rising start timing of the drive current is advanced as the degree of deterioration with time increases. Thus, the fuel injection start timing is advanced, so that the amount of fuel in the cylinder 13 at the time when the fuel is ignited and the premixed combustion starts is increased.

  Further, when the electronic control device 51 advances the rising start timing of the drive current, it also corrects the fuel injection command value for extending the drive current energization period. Thereby, the lift period of the needle valve 23b becomes longer, so that the decrease in the fuel injection rate accompanying the deterioration with time can be suitably suppressed not only in the initial stage of fuel injection but also over a wide range of the fuel injection period. Become.

  Changes in the drive current, the lift amount of the needle valve 23b, and the fuel injection rate due to such correction processing are shown in the time chart of FIG. In the figure, each characteristic line indicated by a broken line is an example (hereinafter referred to as a new example) in the internal combustion engine 11 at the time of a new article, and each characteristic line indicated by a solid line is a fuel with the occurrence of the above-described deterioration with time in the injector 23. This is “this embodiment” in which the correction process of the injection command value is executed. A characteristic line indicated by a one-dot chain line with respect to the lift amount and the fuel injection rate of the needle valve 23b is a comparative example (hereinafter referred to as a deterioration example) in which the above-described correction processing is not performed in the state where the deterioration with time has occurred. . As for the drive current of the electromagnetic valve 23e, this deterioration example has the same characteristics as the new example.

  In the present embodiment, in order to avoid overheating of the solenoid coil of the solenoid valve 23e, the energization at a value is sufficiently smaller than this is continued after the drive current reaches the peak value ip from “0”. It has become. By supplying such drive current to the electromagnetic valve 23e, the needle valve 23b is lifted and fuel is injected from the injector 23.

  Here, looking at the transition of the lift amount of the needle valve 23b, in the above-described deterioration example, the lift start timing is delayed by a crank angle corresponding to the difference angle Δα than in the above-described new example, and the subsequent lift amount increase speed is also delayed. Has occurred. Therefore, in the above-described deterioration example, the maximum lift amount (peak) of the needle valve 23b is smaller than that of the above-mentioned new example by the amount that the start of the lift and the lift amount increase rate are slow, and further, The period until the amount returns to “0” is also shortened.

  As a result, in the above deterioration example, as shown in the figure, the fuel injection rate increase start timing is delayed by the difference angle Δα, the increase rate is also decreased, and the maximum fuel injection rate is further increased. The period until the fuel injection rate returns to “0” is shortened. Thus, the fuel injection amount is reduced.

  In order to suppress such a decrease in the fuel injection amount, in the present embodiment, as shown in the same figure, the fuel injection command value () is set so that the rising start timing of the drive current is advanced by the difference angle Δβ. Here, the command value relating to the fuel injection start timing) is corrected. As a result, the drive current rise completion timing, that is, the timing when the drive current reaches the peak value ip is also advanced by the difference angle Δβ as described above. Therefore, as compared with the new example and the deteriorated example, the drive current is advanced over the entire period from the start to the completion of the rise.

  The difference angle Δβ for the correction is set according to the degree of deterioration with time. That is, as the idle injection amount command value in the ISC is larger than the minimum value S1, the difference angle Δβ is set to be larger because the degree of deterioration with time is larger, and as the idle injection amount command value is closer to the minimum value S1, the difference is increased. Assuming that the degree of deterioration with time is small, the difference angle Δβ is set small.

  By correcting the fuel injection command value in this embodiment, the lift start timing of the needle valve 23b is advanced by the difference angle Δγ (substantially the difference angle Δβ) compared to the deterioration example. Therefore, in the present embodiment, the fuel injection rate increase start timing is advanced by the amount that the lift start timing is advanced earlier than in the deterioration example, and the decrease in the fuel injection rate at the initial stage of fuel injection is suitably suppressed. . As a result, more fuel can be supplied into the cylinder 13 by the start of combustion, and further, atomization of fuel can be promoted at the start of combustion. The reduction can be effectively suppressed. As a result, increase in noise, deterioration in exhaust performance, reduction in engine output, and the like are effectively suppressed.

  In the present embodiment, when the rising start timing of the drive current is advanced, as shown in the figure, the energization period of the drive current is combined with the period T11 of the new product example and the deterioration example. The fuel injection command value (in this case, the command value related to the fuel injection amount) is corrected so as to be extended to the period T12. As a result, the maximum lift amount of the needle valve 23b increases, and the time when the lift amount returns to “0” is delayed. As a result, not only in the initial stage of fuel injection but also over a wide range of the fuel injection period, a decrease in fuel injection rate due to the occurrence of deterioration with time is suppressed, and a decrease in combustion efficiency can be effectively suppressed.

  In the present embodiment, the electronic control unit 51 constitutes a correction unit that corrects the fuel injection command value according to the deterioration with time of the injection characteristics of the injector 23. Further, the electronic control unit 51 feedback-controls the fuel injection command value so as to maintain the steady operation state when the internal combustion engine 11 is in a steady operation state such as an idle operation state, specifically, a maintenance control means for executing ISC. Configure. Further, the electronic control unit 51 constitutes determination means for determining that the degree of deterioration with time has increased when the fuel injection command value feedback-controlled by the maintenance control means has shifted to the side where the fuel injection amount increases.

In the present embodiment, the following effects can be obtained.
(1) The electronic control unit 51 corrects the fuel injection command value so that the rising completion timing of the drive current for opening the injector 23 advances as the degree of deterioration with time increases. As a result, the drive current rise completion timing is advanced, so that the lift amount of the needle valve 23b, that is, the valve opening of the injector 23 is increased earlier. According to this, a decrease in the fuel injection rate at the initial stage of fuel injection is suitably suppressed, and more fuel can be supplied into the cylinder 13 by the start of combustion. A reduction in combustion efficiency can be effectively suppressed by, for example, being able to promote atomization. As a result, increase in noise, deterioration in exhaust performance, reduction in engine output, and the like are effectively suppressed.

  (2) In the present embodiment, the fuel injection command value is corrected so that the rising start timing of the drive current is advanced as the degree of deterioration with time increases. According to this, the rising completion timing of the drive current can be advanced by advancing the energization start timing of the drive current.

  (3) In this embodiment, when the rising start timing of the drive current is advanced, the energization period of the drive current is extended. According to this, not only the initial stage of fuel injection but also a decrease in the fuel injection rate is suitably suppressed over a wide range of the fuel injection period. As a result, an increase in noise, a deterioration in exhaust performance, a decrease in engine output, and the like are further suppressed.

  (4) In the present embodiment, when the fuel injection command value calculated in the ISC executed to maintain the steady operation state of the internal combustion engine 11 such as the idle operation state shifts to the side where the fuel injection amount increases, It was judged that the degree of deterioration increased. According to this, it is possible to appropriately grasp the degree of deterioration with time without providing, for example, a sensor for detecting the position of the needle valve 23b.

  (5) In this embodiment, a direct injection diesel type is adopted as the internal combustion engine 11 to which the present invention is applied. The diesel internal combustion engine 11 self-ignites the fuel by the temperature increase of the air-fuel mixture in the compression stroke. For example, the amount of fuel in the cylinder in the compression stroke is larger than that of an internal combustion engine using an ignition plug such as a gasoline internal combustion engine. The combustion start time and the combustion state tend to be greatly influenced by the atomization state. That is, in the diesel internal combustion engine 11, the effect of suppressing the decrease in the fuel injection rate such as the above (1) to (4) is particularly useful.

In addition, embodiment is not limited above, For example, it is good also as the following aspects.
In the present embodiment in FIG. 6, the rise start timing of the drive current has been advanced so that the lift start timing of the needle valve 23b is earlier than that of the new example. For example, the drive current rising start timing may be advanced within a range where the lift start timing is not earlier than that of a new example.

  In the example of FIG. 6, after the drive current rises and reaches the peak value ip, it is reduced to a value is sufficiently smaller than this, but such a power supply mode is not essential, for example, after reaching the peak value ip, You may make it continue the electric power feeding with the substantially same electric current value as this.

  In the above embodiment, the drive current rise completion timing is advanced through the advance of the drive current rise start timing. However, the present invention is not limited to this. For example, the drive current rise speed is increased. Then, the rising completion timing of the drive current may be advanced. According to this, since the rising speed of the drive current is increased, the period from the rising start time to the rising completion time can be shortened. Therefore, the valve opening degree of the injector 23 can be increased earlier by that amount, and an increase delay in the fuel injection rate due to the deterioration with time can be suppressed.

  In the above embodiment, when delaying the rise completion timing of the drive current, the energization period of the drive current is extended. However, the present invention is not limited to this, for example, the rise completion is completed without extending the energization period. The timing may be retarded.

  In the above embodiment, the degree of deterioration with time is determined based on the fuel injection command value that is feedback-controlled when the internal combustion engine 11 is in the idle operation state. Of these, determination may be made based on a fuel injection command value that is feedback-controlled in an operating state other than the idle operating state. In this case, for example, the degree of deterioration with time is based on the fuel injection command value that is feedback-controlled to maintain this steady operation state when the vehicle travels at a constant accelerator opening and at a constant engine speed. May be determined.

  In the above embodiment, the degree of deterioration with time is determined based on the transition of the fuel injection command value that is feedback-controlled to maintain the steady operation state of the internal combustion engine 11. A sensor for detecting the position of the needle valve 23b may be provided, and the degree of deterioration with time may be determined through the sensor.

  In the above embodiment, a direct injection diesel internal combustion engine is adopted as an internal combustion engine to which the present invention is applied. However, the invention is not limited to this, and a gasoline internal combustion engine, for example, may be used as long as fuel is injected during a compression stroke. May be.

1 is a schematic configuration diagram showing a fuel injection control device for a direct injection internal combustion engine according to an embodiment. Sectional drawing which shows the state before generation | occurrence | production of the time-dependent deterioration concerning the injection characteristic regarding an injector, and after generation | occurrence | production. The figure which shows the relationship between idle injection amount command value and a vehicle total travel distance. The figure which shows transition of a cylinder internal pressure and a fuel injection rate. The flowchart concerning the correction process of a fuel injection command value. The figure which shows the change etc. of the fuel injection rate based on the correction process of a fuel injection command value.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Internal combustion engine, 13 ... Cylinder, 23 ... Injector, 23a ... Housing, 23b ... Needle valve, 23c ... Injection port, 23d ... Seat, 23e ... Electromagnetic valve, 25 ... Common rail, 27 ... Supply pump, 29 ... Fuel tank, 51: Electronic control unit (ECU), 53: Injector drive circuit (EDU).

Claims (6)

In a fuel injection control device for a direct injection internal combustion engine comprising correction means for correcting a fuel injection command value in accordance with deterioration over time according to an injection characteristic of an injector that injects fuel during a compression stroke,
The correction means corrects the fuel injection command value so that a rising completion timing of a drive current for opening the injector is advanced as the degree of deterioration with time increases. A fuel injection control device for an internal combustion engine. The fuel injection control device for a direct injection internal combustion engine according to claim 1,
The fuel injection control device for a direct injection internal combustion engine, wherein the correction means advances a rising start timing of the driving current to advance a rising completion timing of the driving current. The fuel injection control device for a direct injection internal combustion engine according to claim 1 or 2,
The fuel injection control device for a direct injection internal combustion engine, wherein the correction means increases a rising speed of the drive current so as to advance a completion timing of the drive current. In the fuel-injection control apparatus of the direct-injection internal combustion engine as described in any one of Claims 1-3,
The fuel injection control device for a direct injection internal combustion engine, wherein the correction means extends the energization period of the drive current when advancing the rising completion timing of the drive current. In the fuel-injection control apparatus of the direct-injection internal combustion engine as described in any one of Claims 1-4,
Maintenance control means for feedback-controlling the fuel injection command value to maintain the steady operation state when the internal combustion engine is in a steady operation state;
Determining means for determining that the degree of deterioration with time has increased when the fuel injection command value feedback-controlled by the maintenance control means has shifted to the side where the fuel injection amount increases;
A fuel injection control device for a direct injection internal combustion engine. In the fuel injection control device for a direct injection internal combustion engine according to any one of claims 1 to 5,
A fuel injection control device for a direct injection internal combustion engine, wherein the internal combustion engine is a diesel internal combustion engine.

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