JP2007255230A - Fuel injection control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection control device capable of further properly diagnosing the existence of abnormality of a fuel injection valve of a multicylinder internal combustion engine. <P>SOLUTION: This fuel injection control device reduces only a rotation increase quantity DNE 3 by comparing with the other, when abnormality exists in a No. 3 cylinder among rotation increase quantities DNE1 to DNE4 of a crankshaft synchronized with the fuel injection timing of respective cylinders as indicated in Fig. 7(a) by a balloon. Here, this difference is little, and that there is abnormality in the fuel injection valve of the No. 3 cylinder, cannot be determined on the basis of this difference. Here, assuming a No. 1 cylinder and a No. 4 cylinder as a group A and a No.2 cylinder and a No.3 cylinder as a group B, and when setting the fuel injection valve of the No. 3 cylinder as a diagnostic object, fuel injection of the No.2 cylinder is stopped, and the sum total of the rotation increase quantities DNE1 and DNE4 of the group A at this time, is compared with the sum total of the rotation increase quantities DNE2 and DNE3 of the group B. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel injection control device for diagnosing the presence or absence of abnormality of a fuel injection valve based on the behavior of an output shaft caused by fuel injection in each cylinder of a multi-cylinder internal combustion engine.

  As this type of fuel injection control device, for example, as can be seen in Patent Document 1 below, a specific cylinder has a more specific value than the average value of the rotation increase amount of the output shaft synchronized with the injection timing of each cylinder during idle rotation speed control. It has also been proposed to determine that there is an abnormality in the fuel injection valve of the specific cylinder based on the fact that the amount of increase in rotation synchronized with the injection timing is smaller by the determination value. According to this control device, when there is an abnormal fuel injection valve that cannot perform fuel injection, paying attention to the fact that the amount of increase in rotation synchronized with the injection timing of the cylinder is small compared to others, fuel injection The presence or absence of valve abnormality can be diagnosed.

  By the way, in recent years, the structure tends to be designed to reduce the compression rate of the internal combustion engine in order to reduce the resistance when the piston is displaced to the top dead center in the cylinder of the internal combustion engine. For this reason, the rotation fluctuation by each fuel injection is smoothed, and the amount of rotation increase by fuel injection tends to be reduced. In recent years, flywheel dampers that absorb internal combustion engine vibration and output shaft torsion have been improved, and the amount of rotational increase due to each fuel injection tends to be reduced.

  For this reason, even if there is a fuel injection valve that cannot inject fuel, an average of the rotational fluctuation amount synchronized with the injection timing of the cylinder and the rotational increase amount synchronized with the injection timing of each cylinder The difference from the value tends to decrease. On the other hand, the determination value in the control device cannot be a very small value from the viewpoint of keeping the abnormality diagnosis accuracy high. For this reason, it is difficult to detect abnormality of the fuel injection valve by the control device.

Furthermore, in a fuel injection control device of a diesel engine, there is a tendency that multistage injection control is performed in which fuel injection is performed a plurality of times in a single cylinder in one combustion cycle. When the multi-stage injection is performed, the generation period of the output torque due to the fuel injection of each cylinder is extended, so that the amount of fluctuation in rotation between the fuel injections of each cylinder is further reduced. For this reason, in the case of performing multi-stage injection, it is more difficult to diagnose abnormality of the fuel injection valve by the control device.
JP 2001-241353 A

  The present invention has been made to solve the above problems, and an object thereof is to provide a fuel injection control device capable of more appropriately diagnosing the presence or absence of abnormality of a fuel injection valve of a multi-cylinder internal combustion engine. It is in.

  Hereinafter, means for solving the above-described problems and the operation and effects thereof will be described.

  The invention according to claim 1 forcibly changes the operation mode of at least one fuel injection valve with respect to the operation mode determined by the feedback control in order to increase the rotational fluctuation of the output shaft of the multi-cylinder internal combustion engine. And changing means and diagnostic means for diagnosing whether or not any of the fuel injection valves is abnormal based on whether or not there is an increase in rotational fluctuation of the output shaft after the change. .

  In the above configuration, by changing the operation mode of the at least one fuel injection valve, the rotation fluctuation of the output shaft increases unless the fuel injection valve is in a state where fuel injection is not possible. For this reason, the presence or absence of abnormality of the fuel injection valve can be diagnosed by detecting the presence or absence of an increase in the rotational fluctuation and the presence or absence of a change in the operation amount of the fuel injection valve due to the increase in fluctuation. Even if there is an abnormality in the inability to inject fuel, even if the difference between the amount of rotational fluctuation synchronized with the injection timing and the amount of rotational fluctuation synchronized with the injection timing without abnormality is small, the fuel by the fuel injection valve without abnormality By stopping the injection, the rotational fluctuation amount synchronized with the injection timings of both abnormal and stopped injections becomes smaller than the normal rotational fluctuation amount synchronized with the same number of injection timings. For this reason, the presence or absence of abnormality of the fuel injection valve can also be diagnosed based on the magnitude of these rotational fluctuation amounts.

  According to a second aspect of the present invention, in the first aspect of the invention, the changing means is a fuel by a fuel injection valve of any one cylinder of any one of the groups grouped by two cylinders. The diagnosis means forcibly stops the injection, and the diagnosis means outputs the output in which the rotation increase amount of the output shaft synchronized with the fuel injection timing of the arbitrary one group is synchronized with the fuel injection timing of the other group. It is determined that there is an abnormality in the fuel injection valve of the cylinder that has not stopped the injection in the arbitrary group based on being smaller than a predetermined amount than the rotation increase amount of the shaft.

  In the above configuration, the fuel injection by the fuel injection valve of any one of the cylinders in any one group is forcibly stopped. For this reason, the rotation increase amount synchronized with the fuel injection timing of this group becomes smaller than those of the other groups. In particular, when there is an abnormality in the fuel injection valves of the cylinders in which fuel injection is not stopped in the same group, fuel injection is not performed in both cylinders. In particular, it becomes smaller. For this reason, even if the amount of rotational fluctuation due to the inability to perform fuel injection in a single cylinder is small, according to the above processing, when there is an abnormality, the difference in rotational increase between the groups is Can be big.

  According to a third aspect of the present invention, in the second aspect of the present invention, the diagnosis means is configured such that the rotation increase amount of the output shaft synchronized with the fuel injection timing of the arbitrary one group is the fuel injection timing of the other group. When it is detected a predetermined number of times smaller than a rotation increase amount of the output shaft synchronized with the predetermined number of times, if there is an abnormality in the fuel injection valve of the cylinder that did not stop the injection in the arbitrary group It is characterized by judging.

  In the above configuration, an abnormality is determined when it is detected a predetermined number of times that the rotation increase amount of the other group is smaller than the rotation increase amount of any one group by a predetermined amount or more. For this reason, for example, when the rotation speed of the output shaft is detected, the rotation increase amount of the other group is smaller than a predetermined amount than the rotation increase amount of any one group due to noise mixing. However, this makes it possible to avoid making an erroneous determination that there is an abnormality. Therefore, according to the said structure, the presence or absence of abnormality of a fuel injection valve can be diagnosed more appropriately.

  The invention according to claim 4 is the invention according to claim 2 or 3, wherein the comparison of the amount of increase in rotation between the one arbitrary group and the other group does not include a common cylinder. It is the comparison in.

  When a common cylinder is included in different groups, comparing the amount of increase in rotation between groups with overlapping abnormal cylinders can reduce the difference in amount of increase in rotation, and therefore the presence or absence of abnormality can be properly diagnosed. Can not. In this regard, according to the above configuration, since cylinders do not overlap between groups, it is possible to appropriately diagnose whether there is an abnormality.

  According to a fifth aspect of the present invention, in the first aspect of the present invention, in the feedback control, the amount of operation of the fuel injection valve of each cylinder for smoothing the rotational fluctuation of the output shaft due to the fuel injection of each cylinder. Means for calculating a correction amount; and operating means for operating the fuel injection valve with an operation amount corrected by the correction amount, wherein the changing means is configured to correct the corrected one cylinder. A process for forcibly changing the operation amount is performed, and the diagnosis means detects that the fuel injection valve of the cylinder has an abnormality based on a difference between values before and after the correction of the corrected operation amount being a predetermined value or more. It is judged that there exists.

  In the above configuration, in order to forcibly change the corrected operation amount of any one cylinder, if there is no abnormality in the fuel injection valve of any one cylinder, the rotational fluctuation between the cylinders increases. For this reason, the corrected operation amount is updated to reduce the increase in the rotational fluctuation. On the other hand, if there is an abnormality in the fuel injection valve of any one cylinder, the rotational fluctuation between the cylinders does not change despite the change in the corrected operation amount. For this reason, it is considered that the corrected operation amount hardly fluctuates. In the above configuration, paying attention to this property, it is possible to diagnose whether there is an abnormality in the fuel injection valve of any one cylinder.

  According to a sixth aspect of the invention, in the fifth aspect of the invention, the changing means forcibly changes the correction amount, and the diagnosing means has a difference in values before and after the change of the correction amount. It is determined that there is an abnormality in the fuel injection valve of the cylinder based on being above a predetermined value.

  According to the above configuration, the correction amount for suppressing the rotation fluctuation between the cylinders is set as the direct change target and the detection target, so that the change due to the control for suppressing the fluctuation between the cylinders can be detected with higher accuracy. Can do.

  The invention according to claim 7 is the invention according to claim 5 or 6, characterized in that the diagnosis means waits for the diagnosis until a predetermined period elapses after the forced change.

  According to the above configuration, the forced change increases the rotation fluctuation amount between the cylinders, and the diagnosis can be performed when the correction amount is updated so as to compensate for this, so the diagnosis is performed with higher accuracy. be able to.

  The invention according to claim 8 is the invention according to any one of claims 1 to 7, wherein the fuel injection control device performs multi-stage injection control in which fuel is injected a plurality of times in each cylinder within one cycle of combustion. It is characterized by that.

  In the above configuration, in order to perform multi-stage injection, the generation period of the output torque by the fuel injection of each cylinder is extended, and hence the amount of fluctuation in rotation between the cylinders is reduced. For this reason, a difference between the rotational fluctuation amount synchronized with the fuel injection timing of the fuel injection valve incapable of fuel injection and the rotational fluctuation amount synchronized with the fuel injection timing of the normal fuel injection valve is unlikely to occur. It is difficult to diagnose the presence or absence of valve abnormality. For this reason, the said structure can show | play the effect of Claims 1-7 especially suitably.

(First embodiment)
Hereinafter, a first embodiment in which a fuel injection control device according to the present invention is applied to a fuel injection control device of a diesel engine will be described with reference to the drawings.

  FIG. 1 shows the overall configuration of the engine system according to the present embodiment.

  As shown in the figure, the fuel in the fuel tank 2 is pumped up by the fuel pump 6 through the fuel filter 4. The fuel pump 6 includes several plungers. The plunger is reciprocated between the top dead center and the bottom dead center when power is applied from the crankshaft 8 that is an output shaft of the diesel engine, whereby fuel is sucked and discharged. . Specifically, the fuel pump 6 includes a metering valve 10 for metering the amount of fuel discharged from the fuel pump.

  The fuel discharged from the fuel pump 6 is pressurized and supplied (pumped) to the common rail 12. The common rail 12 stores the fuel pumped from the fuel pump 6 in a high pressure state and supplies the fuel to the fuel injection valve 16 of each cylinder (here, four cylinders are illustrated) via the high pressure fuel passage 14. The fuel injection valve 16 is connected to the fuel tank 2 via a low pressure fuel passage 18.

  The engine system includes various sensors that detect the operating state of the diesel engine, such as a crank angle sensor 22 that detects the rotation angle of the crankshaft 8. The engine system also includes an accelerator sensor 24 that detects an operation amount of an accelerator pedal that is operated in response to a user's acceleration request. Further, the engine system includes a vehicle speed sensor 26 that detects a traveling speed of a vehicle on which the engine system is mounted.

  On the other hand, the electronic control unit (ECU 30) is mainly composed of a microcomputer, takes in the detection results of the various sensors, and controls the output of the diesel engine based on this. This output control is basically performed according to the operation amount of the accelerator pedal by the user. However, even when the accelerator pedal is released, the known idle rotation speed control is performed in which the rotation speed of the crankshaft 8 is feedback-controlled to the target value in order to stabilize the operation state of the diesel engine.

  FIG. 2 shows a processing procedure of idle rotation speed control according to the present embodiment. This process is repeatedly executed by the ECU 30, for example, at a predetermined cycle.

  In this series of processing, first, in step S10, it is determined whether or not an execution condition for idle rotation speed control is satisfied. The execution conditions are, for example, (a) the accelerator pedal operation amount detected by the accelerator sensor 24 is substantially zero, (b) the vehicle speed detected by the vehicle speed sensor 26 is substantially zero, and the like. .

  If it is determined that the above condition is satisfied, an injection amount Q for feedback control of the rotational speed of the crankshaft 8 to the target value during idling is calculated in step S12. Here, the injection amount Q is a feedback correction according to the difference between the basic injection amount, which is a feedforward term for control to the target value, and the actual rotational speed based on the detected value of the crank angle sensor 22 and the target value. It is the sum of the quantity ISC.

  In subsequent steps S14 to S26, a process of smoothing the rotational speed of the crankshaft 8 is performed. This is because the rotational speed of the crankshaft 8 increases in synchronization with the fuel injection timing of each cylinder, as shown in FIG. 3A, but the amount of increase may vary among the cylinders. This process is performed.

  Specifically, first, in step S14, an average value DNEA of the rotational increase amount DNEk synchronized with the fuel injection timing of each cylinder is calculated. As shown in FIG. 3A, these rotational increase amounts DNEk are the minimum value of the rotational speed before the rotational speed starts increasing in synchronization with the fuel injection timing of each cylinder, and the maximum value due to the increase of the rotational speed. Is the difference. When the average value DNEA is calculated, in steps S16 to S26, the correction amount FCCB for smoothing the rotation fluctuation between the cylinders is increased in accordance with the magnitude of the rotation increase amount DNEk and the average value DNEA of each cylinder. Or reduce. That is, when the rotational increase amount DNEk is larger than the average value DNEA, the correction amount FCCB is corrected to be decreased by a predetermined amount q in step 20, and when the rotational increase amount DNEk is smaller than the average value DNEA, in step S22. The correction amount FCCB is increased and corrected by a predetermined amount q. When the rotation increase amount DNEk and the average value DNEA are substantially equal, it is desirable not to correct the correction amount FCCB.

  When the correction amount FCCB is corrected for all the cylinders in this way, in step S28, the injection amount required in one combustion cycle for each cylinder is the sum of the injection amount Q and the correction amount FCCB. With this required injection amount, not only the actual rotational speed can be set as the target value, but also variations in rotational speed among the cylinders can be compensated as shown in FIG.

  When the required injection amount is calculated, the required injection amount is divided into a plurality of injection amounts as shown in FIG. This is a process for injecting the required injection amount by a plurality of fuel injections as illustrated in FIG. FIG. 4 shows an example in which two-stage pilot injection p, one-stage main injection, and one-stage after injection are performed. Here, in pilot injection, a very small amount of fuel is injected to promote the mixing of fuel and air immediately before ignition, and the ignition timing delay after main injection is shortened to generate nitrogen oxides (NOx). To reduce combustion noise and vibration. The main injection contributes to the generation of output torque of the diesel engine and has the maximum injection amount during multi-stage injection. After-injection recombusts particulate matter (PM).

  When the process of step S28 is completed, in step S30, the fuel injection valve 16 is operated according to the calculated injection amount. That is, each of the divided injection amounts (injection amounts Q1 to Q4 illustrated in FIG. 4) is used as a command value for the injection amount, and an injection period corresponding to this is calculated. And in order to open the fuel injection valve 16 over this injection period, electricity supply operation with respect to the fuel injection valve 16 is performed.

  When it is determined in step S10 that the execution condition is not satisfied, or when the process of step S30 is completed, this series of processes is temporarily terminated.

  In the above aspect, the rotational speed of the crankshaft 8 can be appropriately controlled to the target value during idling.

  By the way, since the rotational speed is controlled to be constant during idling, the rotational speed of the crankshaft 8 becomes more stable than when the diesel engine is operated according to the accelerator operation of the user. In particular, during idle, feedback control is performed to smooth the rotational fluctuation between the cylinders, so that the rotational speed of the crankshaft 8 becomes more stable. For this reason, if any of the fuel injection valves 16 is in an abnormality that makes injection impossible, it is considered that the rotational speed of the crankshaft 8 varies as shown in FIG. The motivation for diagnosing the presence or absence of abnormality of the fuel injection valve 16 based on the behavior of the shaft 8 has been realized. That is, as illustrated in FIG. 5, when the fuel injection valve 16 of the third cylinder is incapable of being injected, as shown in FIG. 6A, the rotational increase amount DNEk synchronized with the injection timing of the third cylinder. Is greatly deviated from the average value DNEA and falls below a determination threshold set based on the average value DNEA. For this reason, it can be determined that there is an abnormality by detecting that the rotation increase amount DNEk is below the determination threshold.

  However, in recent years, the compression rate tends to be reduced in order to improve the output by reducing the resistance when the piston of each cylinder is displaced to the compression top dead center. When the compression ratio is reduced, rotational fluctuations between the cylinders are suppressed even if there are cylinders that cannot be injected. In recent years, flywheel dampers that suppress vibrations of the diesel engine and torsional force of the crankshaft 8 have been improved, and rotation fluctuations between cylinders tend to be suppressed. Further, in addition to these structural changes, as illustrated in FIG. 4, multistage injection control is performed in which fuel injection is performed a plurality of times within one combustion cycle in a single cylinder. When multi-stage injection is performed, the output torque generation period is extended, so that the amount of increase in rotation shown in FIG. 2 is reduced, and the rotation of the crankshaft 8 is smoothed.

  Thus, due to structural and control changes, it has become difficult to diagnose the presence or absence of an abnormality in the fuel injection valve 16 based on the behavior of the crankshaft 8 during idling. That is, as illustrated in FIG. 5, even when an abnormality that cannot be injected occurs in the fuel injection valve 16 of the third cylinder, the deviation between the rotational increase amount DNE2 and the average value DNEA is reduced. Here, if the difference between the determination threshold value and the average value DNEA is reduced, even when normal fuel injection is performed due to the influence of noise or the like, the difference may be below the determination threshold value. On the other hand, if the determination threshold value is set as usual, as shown in FIG. 6B, even if it is abnormal, the determination threshold value is not lowered. As described above, it is difficult to determine an abnormality with the structural and control changes.

  Therefore, in the present embodiment, during idle rotation speed control, the energization of one fuel injection valve 16 is cut to forcibly stop the injection, thereby intentionally increasing the rotational fluctuation of the crankshaft 8. Then, the presence or absence of abnormality of the fuel injection valve 16 is diagnosed based on the presence or absence of an increase in rotational fluctuation at this time.

  Specifically, the four cylinders are grouped into two groups, and the first and fourth cylinders are group A, and the second and third cylinders are group B. Then, the injection of any one of the fuel injection valves 16 in one group is stopped. Here, the case where the fuel injection valve 16 of the third cylinder cannot be injected is indicated by a circle in FIG. In this case, although only the rotational increase amount DNE3 synchronized with the injection timing of the third cylinder is smaller than the rotational increase amounts DNE1, DNE2, and DNE4 synchronized with the injection timings of the other cylinders, the difference is slight. Therefore, it is difficult to accurately determine that the fuel injection valve 16 of the third cylinder is abnormal. However, as indicated by x in FIG. 7 (a), by stopping the fuel injection by the fuel injection valve 16 of the second cylinder of the same B group, the rotational increase amount DNE3 synchronized with the fuel injection of the B group The sum BDNE of DNE4 is considerably smaller than the sum ADNE of the rotational increase amounts DNE2 and DNE3 synchronized with the fuel injection of the A group. On the other hand, when the fuel injection valve 16 of the third cylinder is normal, the sum BDNE of the B group is equal to the sum ADNE of the A group even if the energization of the fuel injection valve 16 of the second cylinder is cut off. The difference is not so large, though smaller.

  On the other hand, as indicated by a circle in FIG. 7B, when the fuel injection valve 16 of the third cylinder cannot be injected and the energization of the fuel injection valve 16 of the first cylinder is cut off, The sum BDNE of the group and the sum ADNE of the A group are approximate.

  Therefore, based on the difference between the sum BDNE of the B group and the sum ADNE of the A group, the presence or absence of abnormality of the fuel injection valve 16 that is not energized within the energized cut is diagnosed with high accuracy. Can do.

  FIG. 8 shows a processing procedure for diagnosing whether there is an abnormality in the fuel injection valve 16 according to the present embodiment. This process is repeatedly executed by the ECU 30, for example, at a predetermined cycle.

  In this series of processing, when the idling rotational speed control is performed (step S44: YES) and the diagnosis flag is turned on (step S46: YES), abnormality diagnosis of the fuel injection valve 16 is performed (step S46: YES). Step S50). Here, the diagnosis flag is provided in order to perform diagnosis only once after the start switch (ignition switch) of the ECU 30 is turned on until it is turned off. That is, the diagnosis flag is turned on when the ignition switch is switched from OFF to ON (step S40: YES) (step S42), and turned off when the process of step S50 is performed (step S52).

  FIG. 9 shows the process of step S50.

  In this series of processing, this is designated as the k-th cylinder in order from the first cylinder (step S60), the energization of the fuel injection valves 16 in the same group is cut off (step S62), and the system waits for a predetermined time γ ( Step S64). The predetermined time γ is set based on the time that is assumed to be required until the rotation fluctuation of the crankshaft 8 due to the forced injection stop of the specific fuel injection valve 16 converges and a steady state is realized. When it is determined that the predetermined time γ has elapsed, the sum BDNE of the B group and the sum ADNE of the A group are calculated (step S66), and whether or not the absolute value of these differences is greater than the threshold value α. Determine whether. The threshold value α is set based on the minimum value that can be assumed as the difference when the k-th cylinder (cylinder in the same group as the energized cut cylinder) is abnormal.

  If it is determined that the value is larger than the threshold value α, the abnormality counter C is incremented in step S70. The processes in steps S66 to S70 are continued until the determination time ε elapses after the fuel injection in the same group as the k-th cylinder is stopped (step S72). The determination time ε is set to a time that allows the counter value of the abnormality counter C to be a sufficient number when there is an actual abnormality in the fuel injection valve 16 of the k-th cylinder.

  When the determination time ε elapses, it is determined in step S74 whether or not the counter C is equal to or greater than the specified number of times β. The specified number of times β is an erroneous determination that there is an abnormality due to the difference exceeding the threshold value α due to noise mixing in the calculation process of the rotational increase amount DNEk such as acquisition of the detection value of the crank angle sensor 22. It is set to a sufficient number of times to avoid. Actually, the specified number of times β is a value that approximates the number of steps S66 and S68 within the determination time ε, and the misjudgment is avoided by setting the determination time ε and the specified number of times β.

  If it is determined that the number of times is equal to or greater than the predetermined number β, it is determined in step S76 that the k-th cylinder is abnormal, and the process of step S50 of FIG. On the other hand, if it is determined that the number is less than the specified number of times β, while there is a cylinder that is not a diagnosis target, the processes from step S62 to S76 are performed for the cylinder (steps S78 and S80). If there is no abnormality in all the cylinders (step S80: YES), the process of step S50 in FIG.

  According to the embodiment described in detail above, the following effects can be obtained.

  (1) The fuel injection by the fuel injection valve 16 of one of the A group and the B group is forcibly stopped, and the sum of the rotational increases synchronized with the injection of the one group is the other. Based on the fact that it is smaller than the sum of the rotational increase amounts synchronized with the injection of this group by a threshold value α or more, it is determined that the other fuel injection valve 16 of one group is abnormal. Thereby, even in a situation where the amount of fluctuation in rotation due to the inability to perform fuel injection in a single cylinder is small, it is possible to diagnose whether there is an abnormality with high accuracy.

  (2) When the number of times detected to be smaller than the threshold value α is equal to or greater than the specified number β, it is determined that there is an abnormality in the other fuel injection valve 16 of one group. Thereby, it is possible to avoid making an erroneous determination that there is an abnormality even though there is no abnormality, and it is possible to diagnose the presence or absence of abnormality of the fuel injection valve 16 with higher accuracy.

  (3) In a four-cylinder diesel engine, four cylinders were grouped into two groups so as not to include a common cylinder among different groups. Thereby, an appropriate diagnosis can be performed by comparing the sum of the rotational increase amounts of any one group with the sum of the rotational increase amounts of the other groups.

  (4) Multi-stage injection control is performed in which fuel injection is performed a plurality of times in each cylinder within one combustion cycle. For this reason, a difference between the rotational fluctuation amount synchronized with the fuel injection timing of the fuel injection valve 16 incapable of fuel injection and the rotational fluctuation amount synchronized with the fuel injection timing of the normal fuel injection valve 16 hardly occurs. It is difficult to diagnose the abnormality of the fuel injection valve 16. For this reason, this embodiment can show | play especially the effect of said (1)-(3) especially suitably.

(Second Embodiment)
Hereinafter, the second embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  In the present embodiment, the correction amount FCCB for the fuel injection valve 16 to be diagnosed is forcibly changed during the idle speed control shown in FIG. Accordingly, if the target fuel injection valve 16 is normal, the correction amount FCCB should approach the value before the change again by the process of smoothing the rotational fluctuation between the cylinders as shown in FIG. is there. That is, when the rotation state of the crankshaft 8 is steady by the feedback control shown in FIG. 2 (FIG. 10A), for example, for the fourth cylinder, the correction amount FCCB is forcibly increased. Then, the rotational increase amount DNE4 increases (FIG. 10B). However, by the feedback control shown in FIG. 2, the rotational fluctuation caused by the forced change of the correction amount FCCB is smoothed (FIG. 10C). On the other hand, if the target fuel injection valve 16 cannot be injected, the injection amount does not change even if the correction amount FCCB is changed. Therefore, it is considered that the correction amount FCCB does not change much before and after the change.

  In this embodiment, paying attention to this property, the presence or absence of abnormality of the fuel injection valve 16 is diagnosed. FIG. 11 shows a processing procedure for abnormality diagnosis according to the present embodiment. This process is executed by the ECU 30 as the process of step S50 of FIG.

  In this series of processing, this is set as the k-th cylinder in order from the first cylinder (step S82), and the correction amount FCCBk of the k-th cylinder is stored as the value A before the change (step S84). Next, the correction amount FCCBk of the k-th cylinder is forcibly increased by a predetermined amount ΔQ. The predetermined amount ΔQ is set to such a large value that the rotation fluctuation of the crankshaft 8 is detected by the processing shown in FIG. 2 and the correction amount FCCB is corrected. Further, the predetermined amount ΔQ is set to a value that is large enough that the amount of change before and after the change of the correction amount FCCB can be distinguished from the amount of change due to other factors such as noise mixing in the crank angle sensor 22.

  When the correction amount FCCBk of the k-th cylinder is changed in this way, the process waits until the standby time φ elapses (step S88). The waiting time φ is set to a time that is required for the correction process such as the correction amount FCCB to be converged by the process shown in FIG. 2 and the behavior of the crankshaft 8 to be in a steady state. When the waiting time φ has elapsed (step S88: YES), the correction amount FCCBk of the k-th cylinder is acquired as the changed value B in step S90. In a succeeding step S92, it is determined whether or not the absolute value of the difference between the value A and the value B is greater than or equal to the threshold value F. This threshold value F is a value for determining whether or not there is an abnormality in the fuel injection valve 16 of the k-th cylinder. The threshold value F is set to a value that cannot occur as the difference between the value A and the value B after the elapse of the standby time φ when there is no abnormality in the fuel injection valve 16 of the k-th cylinder. If it is determined that the value is greater than or equal to the threshold F, it is determined in step S94 that there is an abnormality in the fuel injection valve 16 of the k-th cylinder.

  The processes in steps S84 to S94 are performed for the fuel injection valves 16 of all the cylinders (steps S96 and S98) unless it is determined that there is an abnormality in any of the cylinders. Then, when the processing of all the cylinders is completed (step S98: YES), or when it is determined that any of the cylinders is abnormal (step S94), the processing of step S50 of FIG. 6 is temporarily performed. finish.

  According to the above processing, as shown in FIG. 12, for example, when the correction amount FCCB of the third cylinder is forcibly increased, if the fuel injection valve 16 of the third cylinder is normal, as indicated by the solid line in the figure. In addition, after the correction amount FCCB is changed, the value changes toward the value A before the change. On the other hand, if the fuel injection valve 16 of the third cylinder is abnormal, as indicated by a broken line in the figure, the value remains almost unchanged after the correction amount FCCB is changed.

  For this reason, after the elapse of the waiting time φ, it is possible to diagnose whether there is an abnormality in the fuel injection valve 16 based on the value A before the change and the value B after the change. In particular, by using the change amount of the correction amount FCCB, it is possible to detect the presence or absence of abnormality with higher accuracy than when using the change amount of the command value of the injection amount for the fuel injection valve 16. This is because only the correction amount FCCB smoothes the rotational fluctuation between the cylinders in the processing shown in FIG. Therefore, by directly monitoring the change in the amount for smoothing the rotational fluctuation between the cylinders, it is possible to directly sense the control operation for smoothing the rotational fluctuation between the cylinders.

  According to the present embodiment described above, in addition to the effect (4) of the first embodiment, the following effect can be obtained.

  (5) During idle rotation speed control, the fuel injection amount of any one cylinder is forcibly changed to the increase side, and the fuel of the cylinder is based on the difference between the value A before the change and the value B after the change. The presence or absence of abnormality of the injection valve 16 was diagnosed. Thereby, the presence or absence of abnormality of the fuel injection valve 16 of the cylinder can be diagnosed.

  (6) Based on the fact that the correction amount FCCB is forcibly changed and the difference between the values before and after the change is equal to or greater than the threshold value F, it is determined that there is an abnormality in the fuel injection valve 16 of the cylinder. Thereby, the presence or absence of abnormality can be diagnosed with higher accuracy.

  (7) By making a diagnosis after the correction amount FCCB is changed and the standby time φ has elapsed, the diagnosis can be made after the behavior of the crankshaft 8 by the process shown in FIG. As a result, diagnosis can be performed more appropriately.

(Other embodiments)
The above embodiments may be implemented with the following modifications.

  In the first embodiment, instead of making an abnormality determination based on the fact that the number of times that the absolute value of the difference between the sum ADNE and the sum BDNE is greater than the threshold value α is equal to or greater than the prescribed number β, the passage of a predetermined time γ Until the determination time ε, the abnormality determination may be made when the absolute value is always larger than the threshold value α.

  In the first embodiment, grouping is performed so as not to include cylinders that are common to different groups. However, the present invention is not limited to this. For example, the A group is the first cylinder and the second cylinder, the B group is the first cylinder and the third cylinder, the C group is the first cylinder and the fourth cylinder, the D group is the third cylinder and the fourth cylinder, and E The group may be the second and fourth cylinders, and the F group may be the second and third cylinders. In this case, when the fuel injection valves 16 of the first cylinder and the second cylinder are to be diagnosed, the sum of the rotation increase amounts of the A group and the sum of the rotation increase amounts of the D group may be compared. Further, when the fuel injection valve 16 of the third cylinder is to be diagnosed, the sum of the B group rotation increase amount and the E group rotation increase amount may be compared. Furthermore, when the fuel injection valve 16 of the fourth cylinder is to be diagnosed, the sum of the rotation increase amounts of the C group and the sum of the rotation increase amounts of the F group may be compared. In short, groups that do not include a common cylinder may be compared.

  -Furthermore, the grouping is not limited to two cylinders as one group. For example, in a 6-cylinder diesel engine, an even-numbered cylinder and an odd-numbered cylinder may be grouped. Here, the diagnosis may be performed based on the sum of the rotational increase amounts of the above groups when the fuel injection of the fuel injection valves 16 of the first cylinder, the third cylinder, and the fifth cylinder is sequentially stopped. That is, in this case, for example, when the fuel injections of the first cylinder and the third cylinder are stopped, the sum of the rotational increase amounts of the even cylinders is larger than the sum of the rotational increase amounts of the odd cylinders, and the fifth cylinder If it is determined that there is an abnormality in the fuel injection valve 16 of the fifth cylinder when the sum of the rotational increases of the even-numbered cylinders does not exceed the threshold more than the sum of the rotational increases of the odd-numbered cylinders. Good. Further, in an eight-cylinder diesel engine, an even cylinder and an odd cylinder may be grouped. Here, for example, when the fuel injection of the fuel injection valve 16 of the first cylinder and the third cylinder is stopped, if there is a large difference in the sum of the rotational increase amounts of the respective groups, the fifth cylinder and the seventh cylinder There may be an abnormality. Therefore, next, if the fuel injection of the fuel injection valve 16 between the first cylinder and the fifth cylinder is stopped and there is no significant difference in the sum of the rotational increase amounts of the above groups, there is an abnormality in the fifth cylinder. Just judge.

  In addition, instead of comparing the sum of the rotation increase amounts of the groups, the average value of the rotation increase amounts of the groups may be compared.

  In the second embodiment, the correction amount FCCB is changed to the increase side, but may be changed to the decrease side. However, since the correction amount FCCB is a minute amount, it is desirable to change it to the increase side in order to cause a significant difference between the value A before the change and the value B after the change.

  Further, instead of changing the correction amount FCCB of a specific cylinder, the final injection amount command value may be changed. Also in this case, as shown in FIG. 2, when the control for smoothing the rotational fluctuation between the cylinders is performed, if the fuel injection valve 16 is normal, the command value of the injection amount is changed. Since it changes before and after and does not change if it is abnormal, diagnosis can be performed based on the value of the injection amount before and after the change.

  In order to increase the rotation fluctuation of the crankshaft 8, the operation mode of the at least one fuel injection valve 16 is forcibly changed with respect to the operation mode determined by the feedback control, and the rotation fluctuation of the crankshaft 8 after the change is increased. The method for diagnosing whether or not any of the fuel injection valves 16 has an abnormality based on the presence or absence of this is not limited to those exemplified in the above embodiments and modifications thereof. For example, when the injection amount of the fuel injection valve 16 to be diagnosed is changed to an increase side to such an extent that a change in the rotation increase amount can be clearly detected, and the increase in the rotation increase amount is not detected at that time, the target It may be determined that the fuel injection valve 16 is abnormal.

  In each of the above embodiments, the present invention is applied to a diesel engine. However, the present invention is not limited to this and may be applied to a gasoline engine. Even in this case, the application of the present invention is particularly effective because the above-described problems occur when the compression ratio is reduced by the structural improvement of the gasoline engine or the flywheel damper is improved. It is.

The figure which shows the whole structure of the engine system of 1st Embodiment. The flowchart which shows the process sequence of idle rotation speed control concerning the embodiment. The figure explaining the method of control which smoothes the rotation fluctuation between the cylinders concerning the embodiment. The time chart which shows the aspect of the fuel-injection control concerning the embodiment. The figure for demonstrating the problem in the diagnosis of the presence or absence of abnormality of a fuel injection valve. The figure for demonstrating the problem in the diagnosis of the presence or absence of abnormality of a fuel injection valve. The figure explaining the diagnostic method of the presence or absence of abnormality of the fuel injection valve concerning the said embodiment. The flowchart which shows the process sequence of the diagnosis of the presence or absence of abnormality of the fuel injection valve concerning the embodiment. The flowchart which shows the process sequence of the diagnosis of the presence or absence of abnormality of the fuel injection valve concerning the embodiment. The figure explaining the diagnostic method of the presence or absence of abnormality of the fuel injection valve concerning 2nd Embodiment. The flowchart which shows the process sequence of the diagnosis of the presence or absence of abnormality of the fuel injection valve concerning the embodiment. The time chart which shows the diagnostic aspect of the presence or absence of abnormality of the fuel injection valve concerning the said embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 8 ... Crankshaft, 16 ... Fuel injection valve, 22 ... Crank angle sensor, 30 ... ECU (one Embodiment of a fuel-injection control apparatus).

Claims (8)

In a fuel injection control device that feedback-controls the rotation speed of an output shaft to a target value by operating a fuel injection valve provided for each cylinder of a multi-cylinder internal combustion engine.
Change means for forcibly changing the operation mode of at least one fuel injection valve with respect to the operation mode determined by the feedback control in order to increase the rotational fluctuation of the output shaft of the multi-cylinder internal combustion engine;
A fuel injection control device comprising: a diagnosis means for diagnosing whether or not any of the fuel injection valves is abnormal based on the presence or absence of an increase in rotation fluctuation of the output shaft after the change. . The changing means forcibly stops the fuel injection by the fuel injection valve of any one cylinder of any one of the groups grouped by two cylinders,
The diagnosis means has a rotation increase amount of the output shaft synchronized with the fuel injection timing of the arbitrary one group being smaller than a predetermined amount than a rotation increase amount of the output shaft synchronized with the fuel injection timing of the other group. 2. The fuel injection control device according to claim 1, wherein the fuel injection control device determines that there is an abnormality in the fuel injection valve of the cylinder that has not stopped the injection in the arbitrary group.   The diagnosis means has a rotation increase amount of the output shaft synchronized with the fuel injection timing of the arbitrary one group being smaller than a predetermined amount than a rotation increase amount of the output shaft synchronized with the fuel injection timing of the other group. 3. The fuel injection control device according to claim 2, wherein when is detected a predetermined number of times, it is determined that there is an abnormality in a fuel injection valve of a cylinder that has not stopped the injection in the arbitrary group. .   4. The fuel according to claim 2, wherein the comparison of the rotational increase amount between the one arbitrary group and the other group is a comparison between groups not including a common cylinder. Injection control device. At the time of the feedback control, means for calculating a correction amount of the operation amount of the fuel injection valve of each cylinder for smoothing the rotation fluctuation of the output shaft due to the fuel injection of each cylinder, and the correction amount is corrected An operation means for operating the fuel injection valve with an operation amount;
The changing means performs a process of forcibly changing the corrected operation amount for any one cylinder,
2. The fuel according to claim 1, wherein the diagnosis unit determines that there is an abnormality in the fuel injection valve of the cylinder based on a difference between values before and after the correction of the corrected operation amount being a predetermined value or more. Injection control device. The changing means forcibly changes the correction amount,
6. The fuel injection control device according to claim 5, wherein the diagnosis unit determines that there is an abnormality in the fuel injection valve of the cylinder based on a difference between values before and after the change of the correction amount being a predetermined value or more. .   7. The fuel injection control device according to claim 5, wherein the diagnosis unit waits for performing the diagnosis until a predetermined period elapses after the forced change.   The fuel injection control device according to any one of claims 1 to 7, wherein the fuel injection control device performs multi-stage injection control in which fuel injection is performed a plurality of times in each cylinder within one cycle of combustion.

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