JP2016156299A - Failure diagnostic device of fuel injection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a failure diagnostic device which can be completed in a common rail system and can diagnose failure of a fuel pressure sensor even when a fuel injection valve fails.SOLUTION: A failure diagnostic device (50) applied to a fuel injection system (10) having a pressure accumulating chamber (20), a plurality of fuel injection valves (40) and a fuel pressure sensor (22) includes injection execution means for executing fuel injection on a predetermined injection condition with remaining fuel injection valves when fuel injection is executed by one fuel injection valve on the predetermined injection condition, detected drop amount calculating means for calculating a drop amount of a fuel pressure in the pressure accumulating chamber as a detected drop amount, estimated drop amount calculating means for calculating an estimated drop amount of the fuel pressure in the pressure accumulating chamber as an estimated drop amount, fluctuation calculating means for calculating fluctuation in the detected drop amount, and fuel pressure sensor failure determination means for determining failure of the fuel pressure sensor when the fluctuation is within a first prescribed range and the difference between the detected drop amount and the estimated drop amount is outside a second prescribed range.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a failure diagnosis device for diagnosing a failure in a fuel injection system.

  2. Description of the Related Art As a fuel injection device for a diesel engine, one having a common pressure accumulation chamber (common rail) for supplying high-pressure fuel to a fuel injection valve of each cylinder is well known. According to this common rail type diesel engine, the fuel pressure in the common rail can be freely controlled according to the engine operating state, and as a result, the fuel pressure supplied to the fuel injection valve can be freely controlled.

  In such a fuel injection device, there is a problem that fuel injection cannot be properly controlled if the fuel pressure sensor fails and the accurate fuel pressure cannot be detected.

  Regarding the failure detection of the fuel pressure sensor, there is a prior art described in Patent Document 1, for example. In Patent Document 1, the injection amount is estimated from the fluctuation amount of the output of the internal combustion engine when the required injection amount is changed, and the fuel pressure is estimated from the injection amount. Then, when one point determined by the estimated fuel pressure and the fuel pressure detected by the fuel pressure sensor is not within the normal range, it is determined that the pressure sensor has a failure. Further, by grasping how the determined point deviates from the central characteristic value, it is determined what kind of property the failure of the fuel pressure sensor is specifically.

JP2007-40113

  However, the prior art described in Patent Document 1 has a configuration in which a sensor for detecting the output of a diesel engine is essential, and it is difficult to say that the failure diagnosis device is completed within the common rail system. Further, it may be determined that the fuel pressure sensor has failed, even when the fuel pressure fluctuates due to a failure of the fuel injection valve.

  The present invention has been made in order to solve the above-mentioned problems, and its main purpose is a failure that can be completed within the common rail system and can diagnose the failure of the fuel pressure sensor even when there is a failure of the fuel injection valve. It is to provide a diagnostic device.

  The present invention includes a pressure accumulation chamber that stores high-pressure fuel, a fuel pump that pressurizes and discharges fuel supplied to the pressure accumulation chamber, and a plurality of fuel injection valves that inject fuel stored in a high pressure state in the pressure accumulation chamber; And a fuel pressure sensor for detecting a fuel pressure in the pressure accumulating chamber, wherein the fault diagnosis device is applied to a fuel injection system with a predetermined injection condition by one of the plurality of fuel injection valves. When fuel injection is executed, injection execution means for executing fuel injection under the predetermined injection condition by the remaining fuel injection valves, and caused by injection by the fuel injection valve under the predetermined injection condition With the amount of decrease in the fuel pressure in the pressure accumulating chamber as a detected amount of decrease, a detection decrease amount calculation means for calculating based on the detection value of the fuel pressure sensor, and the injection by the fuel injection valve under the predetermined injection condition An estimated descent amount calculating means for calculating an estimated descent amount of the fuel pressure drop in the pressure accumulating chamber between the plurality of fuel injection valves and the detected descent amount calculated by the detected descent amount calculating means. A variation calculating means for calculating a variation at the time, and the variation calculated by the variation calculating means is within a first predetermined range, and the detected drop amount and the estimated drop amount calculated by the detected drop amount calculating means And a fuel pressure sensor failure determination means for determining that the fuel pressure sensor has failed when the difference from the estimated amount of descent calculated by the means is out of the second predetermined range.

  According to the above configuration, the fuel injection system includes the pressure accumulation chamber, the fuel pump, the fuel injection valve, and the fuel pressure sensor. This failure diagnosis apparatus for a fuel injection system includes injection execution means, and when the fuel is injected under a predetermined injection condition by one of the plurality of fuel injection valves, the remaining fuel The fuel is injected under the predetermined injection condition by the injection valve. When all the cylinders are controlled to perform fuel injection under predetermined injection conditions, the amount of fuel pressure drop in the accumulator chamber caused by the injection by the fuel injection valve is detected as a detected drop amount by the detected drop amount calculating means. Calculated. The variation of the detected drop amount calculated between the plurality of fuel injection valves is calculated by the variation calculating means. Further, based on the target injection amount of the fuel injected from the fuel injection valve, the estimated pressure drop amount calculating means calculates the fuel pressure drop amount in the pressure accumulating chamber that is estimated to be caused by the injection as the estimated drop amount.

  When the fuel pressure sensor is out of order, the detected drop amount calculated with respect to the estimated drop amount estimated to be caused by the injection is shifted in a large or small direction. The amount of difference from the amount is out of the second predetermined range in all the fuel injection valves. In addition, since the same deviation is caused in all the fuel injection valves, the variation in the detected drop amount calculated among the plurality of fuel injection valves calculated by the variation calculation means falls within the first predetermined range. Accordingly, the variation calculated by the variation calculation means is within the first predetermined range, and the difference between the detected fall amount calculated by the detected fall amount calculation means and the estimated fall amount calculated by the estimated fall amount calculation means is When the fuel pressure sensor is out of the second predetermined range, the fuel pressure sensor failure determination means determines that the fuel pressure sensor has failed. When there is a failure of the fuel injection valve, the detected drop amount of the failed fuel injection valve among the plurality of fuel injection valves is different from the detected drop amount of the other fuel injection valves. The variation in the detected drop amount between the fuel injection valves does not fall within the first predetermined range. For this reason, it is possible to diagnose the failure of the fuel pressure sensor even when there is a failure of the fuel injection valve. Further, the configuration is completed only by the fuel injection system, and an external configuration such as a sensor for detecting the output of the internal combustion engine is not required.

  The present invention also provides a pressure accumulation chamber that stores high-pressure fuel, a fuel pump that pressurizes and discharges fuel supplied to the pressure accumulation chamber, and a plurality of fuel injections that inject fuel stored in a high pressure state in the pressure accumulation chamber A failure diagnosis device applied to a fuel injection system comprising a valve and a fuel pressure sensor for detecting fuel pressure in the pressure accumulating chamber, wherein a predetermined injection is performed by one of the plurality of fuel injection valves When fuel injection is executed under conditions, injection execution means for executing fuel injection under the predetermined injection conditions by the remaining fuel injection valves, and accompanying injection by the fuel injection valves under the predetermined injection conditions The amount of fuel pressure drop that has occurred in the accumulator chamber that has occurred is used as a detected drop amount, and the detected drop amount calculation means calculates the detection pressure based on the detected value of the fuel pressure sensor, and the injection by the fuel injection valve under the predetermined injection condition An estimated descent amount calculating means for calculating an estimated descent amount of the fuel pressure drop in the pressure accumulating chamber estimated to be generated, and a majority from the detected descent amount for each cylinder calculated by the detected descent amount calculating means. A difference amount calculating means for selecting the detected drop amount as a majority drop amount and calculating a difference amount based on a difference between the majority drop amount and the estimated drop amount calculated by the estimated drop amount calculating means; Fuel pressure sensor failure determination means for determining a failure of the fuel pressure sensor when the difference amount calculated by the amount calculation means is out of the second predetermined range.

  According to the above configuration, the fuel injection system includes the pressure accumulation chamber, the fuel pump, the fuel injection valve, and the fuel pressure sensor. This failure diagnosis apparatus for a fuel injection system includes injection execution means, and when the fuel is injected under a predetermined injection condition by one of the plurality of fuel injection valves, the remaining fuel The fuel is injected under the predetermined injection condition by the injection valve. When all the cylinders are controlled to perform fuel injection under predetermined injection conditions, the amount of fuel pressure drop in the accumulator chamber caused by the injection by the fuel injection valve is detected as a detected drop amount by the detected drop amount calculating means. Calculated. Further, based on the target injection amount of the fuel injected from the fuel injection valve, the estimated pressure drop amount calculating means calculates the fuel pressure drop amount in the pressure accumulating chamber that is estimated to be caused by the injection as the estimated drop amount. When the fuel pressure sensor is out of order, there is a shift in the detected drop amount of all cylinders in the large or small direction with respect to the estimated drop amount that is expected to be caused by the injection. All the difference amounts thus made are out of the second predetermined range. When determining whether or not such a fuel pressure sensor failure has occurred, it is not necessary to determine whether or not the detected drop amount is deviated from the estimated drop amount in all the fuel injection valves. This is because there is a small possibility that the failure of the fuel injection valves that should be determined as failure by distinction will be more than a majority at the same time, so there are more fuel injection valves than the majority in which the detected drop amount deviates from the estimated drop amount This is because it can be determined that the fuel pressure sensor has failed. Therefore, the detected fall amount exceeding the majority is selected as the majority fall amount from all the calculated fall amounts, and the difference amount based on the difference between the majority fall amount and the estimated fall amount calculated by the estimated fall amount calculation means is calculated. Calculated by the difference amount calculation means. When the calculated difference amount is larger than the majority of fuel injection valves that are out of the second predetermined range, the fuel pressure sensor failure determination means determines that the fuel pressure sensor has failed. Therefore, even with such a fuel pressure sensor failure determination, it is possible to make a diagnosis in distinction from a fuel injection valve failure. Further, the configuration is completed only by the fuel injection system, and an external configuration such as a sensor for detecting the output of the internal combustion engine is not required.

It is a schematic structure figure of a fuel injection system concerning this embodiment. It is a control flowchart performed by ECU concerning this embodiment. It is a figure which shows the behavior at the time of fuel injection valve abnormality concerning this embodiment, and pressure sensor output abnormality. It is an example regarding the output abnormality of a pressure sensor. It is an example regarding the output abnormality of a pressure sensor. It is a figure which shows the pump discharge amount and feedback amount at the time of pressure sensor output abnormality. It is a modification of the control flowchart shown by FIG.

  Hereinafter, the present embodiment will be described with reference to the drawings. FIG. 1 shows a fuel injection system 10 of the present embodiment.

  The pressure accumulation fuel injection system 10 includes a fuel supply pump 16 (corresponding to a fuel pump), a common rail 20 (corresponding to a pressure accumulating chamber), a pressure sensor 22 (corresponding to a fuel pressure sensor), a pressure reducing valve 30, a plurality of fuel injection valves 40, An electronic control unit (ECU) 50, an electronic driving unit (EDU) 52, and the like, each of a four-cylinder diesel engine (hereinafter also simply referred to as an engine) not shown as an internal combustion engine. Fuel is injected into the cylinder. In FIG. 1, only the control signal line from the EDU 52 to one fuel injection valve 40 and the injection pipe 202 from the common rail 20 to one fuel injection valve 40 are shown in order to avoid the complexity of the figure. Yes.

  The fuel filter 14 removes foreign matters in the fuel sucked by the fuel supply pump 16 from the fuel tank 12. The fuel supply pump 16 has a built-in feed pump that sucks fuel from the fuel tank 12, pressurizes the sucked fuel, and discharges it to the common rail 20 through the supply pipe 200.

  The fuel supply pump 16 is a known pump that pressurizes the fuel sucked into the pressurizing chamber when the plunger reciprocates as the cam of the camshaft rotates. By controlling the metering valve 18 of the fuel supply pump 16 by the ECU 50, the amount of fuel sucked by the fuel supply pump 16 in the suction stroke is metered. Then, the amount of fuel discharged from the fuel supply pump 16 is adjusted by adjusting the intake amount. It should be noted that a metering valve for metering the fuel discharge amount may be installed on the discharge side of the fuel supply pump 16 to meter the discharge amount.

  The common rail 20 accumulates the fuel discharged from the fuel supply pump 16 to maintain the fuel pressure at a predetermined high pressure corresponding to the engine operating state, and supplies the fuel to the fuel injection valve 40 through the injection pipe 202. The pressure sensor 22 outputs a signal corresponding to the fuel pressure (actual rail pressure) inside the common rail 20.

  The pressure reducing valve 30 is an electromagnetic valve that opens by energization control and discharges the fuel inside the common rail 20 to the return pipe 204 on the low pressure side.

  The fuel injection valve 40 is mounted in each cylinder of a four-cylinder diesel engine, and injects fuel accumulated in the common rail 20 into the cylinder. The fuel injection valve 40 performs multi-stage injection including pilot injection and post injection before and after the main injection in one combustion cycle based on the operating state of the engine. The fuel injection valve 40 is a known electromagnetically driven injection valve that controls the fuel injection amount by controlling the pressure in the back pressure chamber that applies fuel pressure to the nozzle needle in the valve closing direction. The electromagnetic drive unit of the fuel injection valve 40 is constituted by a piezo actuator or an electromagnetic coil.

  The back pressure control valve 42 opens when the pressure in the back pressure chamber of the fuel injection valve 40 exceeds a predetermined pressure, and discharges the fuel in the back pressure chamber to the return pipe 204. This prevents the pressure in the back pressure chamber of the fuel injection valve 40 from exceeding a predetermined pressure.

  The ECU 50 is mainly composed of a microcomputer (microcomputer) mainly including a rewritable nonvolatile memory such as a CPU, a ROM, a RAM, and a flash memory, an input / output interface, and the like.

  The ECU 50 executes various controls of the fuel injection system 10 by executing a control program stored in the ROM or flash memory. For example, the ECU 50 controls the discharge amount of the fuel supply pump 16 and the opening / closing of the pressure reducing valve 30 to detect the detected rail pressure from the output signal of the pressure sensor 22 and the target pressure (target) set based on the engine operating state. The feedback (F / B) control is executed to make the detected rail pressure follow the target rail pressure based on the differential pressure with respect to the rail pressure (corresponding to feedback control means).

  The ECU 50 includes an injection executing means, a detected drop amount calculating means, an estimated drop amount calculating means, a variation calculating means, a fuel pressure sensor failure determining means, a feedback amount determining means, a deviation direction specifying means, a fuel injection valve failure determining means according to the present invention, It has functions such as a difference amount calculating means and a failure injection valve specifying means.

  The EDU 52 is a drive device for supplying drive current or drive voltage to the pressure reducing valve 30 and the fuel injection valve 40 based on a control signal output from the ECU 50.

  Hereinafter, the control content regarding the fuel injection system 10 which ECU50 performs is demonstrated. The control related to the fuel injection system 10 shown in FIG. 2 is repeatedly executed by the ECU 50 at a predetermined cycle during the power-on period of the ECU 50.

  When this control is activated, it is first determined in step 100 whether or not a diagnostic condition is satisfied. The diagnosis condition indicates that one of the four cylinders is in a specific operation state (corresponding to a predetermined injection condition). Specifically, the target rail pressure in the common rail 20 becomes the predetermined pressure PFIN, and the command injection amount instructed to the fuel injection valve 40 according to the predetermined pressure PFIN is set to the predetermined injection amount QFIN. When the diagnosis condition is not satisfied (step 100: NO), this control is finished as it is. If the diagnosis condition is satisfied (step 100: YES), the process proceeds to step 101.

  In step 101, the same injection condition is set for the other cylinders when the diagnosis condition is satisfied. Specifically, as shown in FIG. 3, when the diagnosis condition for the # 1 cylinder is satisfied, the target rail pressure is set to the predetermined pressure PFIN and the command injection amount is set to the predetermined injection amount QFIN for the cylinders after # 2. To do.

  Thereafter, in step 102, the detected rail pressures that have decreased due to the fuel injection from the fuel injection valve 40 provided in each cylinder are calculated based on the signal from the pressure sensor 22, respectively.

  In step 103, the differential pressure between the detected rail pressure in the common rail 20 before injection and the detected rail pressure after fuel injection calculated in step 102 is calculated for each cylinder as a detected differential pressure ΔPk.

  In step 104, the variation X between cylinders is calculated from the calculated detected differential pressure ΔPk of each cylinder. In the present embodiment, the standard deviation is calculated using the calculated detected differential pressure ΔPk of each cylinder. This calculated standard deviation corresponds to the variation X between cylinders.

  In step 105, it is determined whether or not the calculated variation X between cylinders is within the first predetermined range α. The first predetermined range α is set as a range including an error in the variation X between cylinders that is expected to be calculated when the pressure sensor 22 and the fuel injection valves 40 of all the cylinders are not out of order. At this time, for example, as shown in FIG. 3, if the fuel injection valve 40 of the # 3 cylinder is out of order, the detected differential pressure ΔPk of the # 3 cylinder shows a different value compared to the other cylinders. Variation X deviates from the first predetermined range α. Therefore, when the variation X between the cylinders does not fall within the first predetermined range α (step 105: NO), the process proceeds to step 106, and it is determined that there is a cylinder in which the fuel injection valve 40 has failed. And when it determines with the fuel injection valve 40 having failed, the fuel injection valve 40 is out of order about the fuel injection valve 40 of the cylinder which shows a value different from detection differential pressure (DELTA) Pk of the cylinder exceeding a majority. Is identified. The detected differential pressure ΔPk of the cylinder exceeding the majority refers to a plurality of detected differential pressures ΔPk whose difference is within a predetermined value, the number of which exceeds the majority.

  When the variation X between the cylinders falls within the first predetermined range α (step 105: YES), the routine proceeds to step 107. In step 107, the estimated differential pressure ΔPt as the differential pressure in the cylinder generated when the fuel is injected under a predetermined injection condition estimated to be calculated when the pressure sensor 22 and the fuel injection valve 40 are not malfunctioning. And whether or not there is a difference between the detected differential pressure ΔPk of a certain cylinder. For example, as shown in FIG. 3, when the output of the pressure sensor 22 is abnormal, the detected differential pressure ΔPk causes a certain deviation from the estimated differential pressure ΔPt in all cylinders. Therefore, in this embodiment, when the quotient (corresponding to the difference amount) obtained by dividing the detected differential pressure ΔPk by the estimated differential pressure ΔPt does not fall within the second predetermined range β, it is determined that there is a difference. In addition, since the failure determination of the fuel injection valve 40 has already been performed, it is not necessary to consider the failure of the fuel injection valve 40 when determining the failure of the pressure sensor 22. Therefore, it is not determined whether there is a difference between the detected differential pressure ΔPk and the estimated differential pressure ΔPt in all cylinders, but it is determined whether there is a difference between the detected differential pressure ΔPk and the estimated differential pressure ΔPt in one cylinder. The second predetermined range β is set as a range including an error in the quotient obtained by dividing the detected differential pressure ΔPk expected when the pressure sensor 22 and the fuel injection valve 40 are normal by the estimated differential pressure ΔPt.

  When the quotient obtained by dividing the detected differential pressure ΔPk by the estimated differential pressure ΔPt falls within the second predetermined range β (when there is no difference between the estimated differential pressure ΔPt and the detected differential pressure ΔPk of a certain cylinder) (step 107) : YES), this control is finished as it is. When the quotient obtained by dividing the detected differential pressure ΔPk by the estimated differential pressure ΔPt does not fall within the second predetermined range β (when there is a difference between the estimated differential pressure ΔPt and the detected differential pressure ΔPk of a certain cylinder) (step) 107: NO), the process proceeds to step 108, and it is determined that the pressure sensor 22 has failed.

  In step 109, it is determined how the output of the pressure sensor 22 deviates from the detected rail pressure that is originally detected. At this time, for example, when the output of the pressure sensor 22 deviates from the center characteristic as shown in FIG. 4, the quotient obtained by dividing the detected differential pressure ΔPk by the estimated differential pressure ΔPt is calculated as a value larger than the second predetermined range β. The This indicates that the detected differential pressure ΔPk is larger than the estimated differential pressure ΔPt, that is, the detected rail pressure (pressure sensor recognition pressure) although injection is performed with the assumed injection pulse. ) Means below the expected value. It is known that there is a correlation between the actual rail pressure and the fuel injection amount, and the higher the actual rail pressure before injection, the larger the fuel injection amount that is injected. Therefore, the fact that the detected rail pressure was lower than the expected value even though the injection was carried out with the assumed injection pulse means that the actual rail pressure before the injection was so high that more fuel was expected than expected. It is injected and the detected rail pressure is greatly reduced. That is, it can be seen that the detected rail pressure detected by the pressure sensor 22 is detected as a value smaller than the actual rail pressure that should be detected. Further, even when compared with the central characteristic, the detected rail pressure is detected at a low value.

  However, as shown in FIG. 5, when the detected rail pressure is higher than the central characteristic before fuel injection and the detected rail pressure greatly decreases across the central characteristic after fuel injection, the deviation of the output of the pressure sensor 22 is performed by the above method. Is difficult to identify. This is because, in this case, the detected differential pressure ΔPk is calculated to be larger than the estimated differential pressure ΔPt, but when the injection is started under a predetermined injection condition, the output of the pressure sensor 22 is shifted in a large direction with respect to the central characteristic. Nevertheless, it is erroneously determined that the output of the pressure sensor 22 is shifted in a small direction with respect to the center characteristic. In this embodiment, in order to suppress such erroneous determination, attention is paid to the actual feedback amount F of the fuel injection amount when the F / B control is performed so that the detected rail pressure in the common rail 20 is set to the predetermined pressure PFIN.

  In the output abnormality of the pressure sensor 22 shown in FIG. 5, since the actual rail pressure before fuel injection is lower than the center characteristic, the fuel injection amount is also small. Since the fuel injection amount and the discharge amount of the fuel supply pump 16 have a correlation, as shown in FIG. 6, the discharge amount of the fuel supply pump 16 is also smaller than the discharge amount of the fuel supply pump 16 measured at the time of shipment. I understand. The discharge amount at this time is obtained by adding the actual feedback amount F when the F / B control is performed so that the detected rail pressure becomes the target rail pressure to the basic pumping amount set according to the target rail pressure. is there. That is, the actual feedback amount F is directly affected when the output of the pressure sensor 22 is abnormal. Therefore, in the present embodiment, it is determined whether the actual feedback amount F is larger or smaller than the initial feedback amount FB as an initial value (default feedback amount at the time of shipment) of the feedback amount in a predetermined injection condition. It is determined which of 22 outputs is shifted with respect to the center sensor.

  According to FIG. 6, the actual feedback amount F of each cylinder when the output of the pressure sensor 22 is abnormal is smaller than the initial feedback amount FB. The fact that the actual feedback amount F is smaller than the initial feedback amount FB when the pressure sensor 22 is normal means that the detected differential pressure ΔPk is larger than the estimated differential pressure ΔPt, but actually injected. This shows that the amount of fuel injection performed is smaller than the amount of fuel injection measured at the time of shipment. That is, the output of the pressure sensor 22 is shifted in a direction larger than the center characteristic, and the actual rail pressure is lower than the detected rail pressure, so that the fuel injection amount is smaller than that at the time of shipment. I understand.

  Therefore, in step 109, in order to specify the displacement direction of the pressure sensor 22, it is determined whether the actual feedback amount F of each actual cylinder is larger than the initial feedback amount FB. When the actual feedback amount F of each actual cylinder is not larger than the initial feedback amount FB (S109: NO), it is determined that the pressure sensor 22 has shifted in a large direction with respect to the center characteristic, and this control is performed. finish. When the actual feedback amount F of each cylinder is larger than the initial feedback amount FB when the pressure sensor 22 is normal (S109: YES), the pressure sensor 22 is shifted in a small direction with respect to the central characteristic. This control is terminated.

  With the above configuration, the control device for an internal combustion engine according to the present embodiment has the following effects.

  The ECU 50 calculates the amount of decrease in the detected rail pressure in the common rail 20 caused by the injection by the fuel injection valve 40 for each cylinder as the detected differential pressure ΔPk. A variation X of the detected differential pressure ΔPk calculated between the plurality of fuel injection valves 40 is calculated. Further, the fuel pressure drop amount in the common rail 20 that is estimated to be caused by the injection based on the predetermined injection amount QFIN is calculated as the estimated differential pressure ΔPt. When the pressure sensor 22 is out of order, the detected differential pressure ΔPk calculated with respect to the estimated differential pressure ΔPt is shifted in a large or small direction. Therefore, the detected differential pressure ΔPk is divided by the estimated differential pressure ΔPt. The quotient deviates from the second predetermined range β in all the fuel injection valves 40. Further, since the same deviation is caused in all the fuel injection valves 40, the variation X of the detected differential pressure ΔPk calculated among the plurality of fuel injection valves 40 is within the first predetermined range. Accordingly, when the calculated variation X is within the first predetermined range and the quotient obtained by dividing the detected differential pressure ΔPk by the estimated differential pressure ΔPt is out of the second predetermined range β, a failure of the pressure sensor 22 is determined. . When there is a failure in the fuel injection valve 40, the detected differential pressure ΔPk of the failed fuel injection valve 40 among the plurality of fuel injection valves 40 is different from the detected differential pressure ΔPk of the other fuel injection valves 40. The variation X of ΔPk calculated between the injection valves 40 does not fall within the first predetermined range α. For this reason, even when there is a failure in the fuel injection valve 40, it is possible to diagnose a failure in the pressure sensor 22. Further, the configuration is completed only by the fuel injection system 10, and an external configuration such as a sensor for detecting the output of the internal combustion engine is not required.

  The ECU 50 provides feedback (F / F) that causes the detected rail pressure to follow the target rail pressure based on the differential pressure between the detected rail pressure detected from the output signal of the pressure sensor 22 and the target rail pressure set based on the engine operating state. B) Control is executed. When the failure of the pressure sensor 22 is determined, it is determined whether the actual feedback amount F is larger or smaller than the initial feedback amount FB as an initial value of the feedback amount under a predetermined injection condition. Based on this determination, the ECU 50 specifies the deviation direction of the output of the pressure sensor 22 with respect to the actual rail pressure in the actual common rail 20. For example, when the actual feedback amount F actually controlled is smaller than the initial feedback amount FB, the actual rail pressure is lower than the detected rail pressure, so the fuel injection amount is smaller than that at the time of shipment. I understand that. Therefore, it can be seen that the output of the pressure sensor 22 is shifted in a large direction with respect to the center characteristic. Therefore, by considering the change in the actual feedback amount F, it is possible to specify how the output of the pressure sensor 22 has deviated from the change in the actual rail pressure.

  When the ECU 50 determines that the fuel injection valve 40 has not failed, it is determined whether or not the pressure sensor 22 has failed. For this reason, it becomes possible to distinguish and determine the failure of the fuel injection valve 40 and the failure of the pressure sensor 22.

  When the ECU 50 determines that the fuel injection valve 40 is out of order, the calculated detected differential pressure ΔPk is compared between the cylinders, and a detected differential pressure ΔPk that is different from the detected differential pressure ΔPk of the cylinder exceeding the majority is calculated. For each cylinder, it is specified that the fuel injection valve 40 of that cylinder has failed. For this reason, it becomes possible not only to determine the failure of the fuel injection valve 40 but also to identify which cylinder of the fuel injection valve 40 is in failure.

  The diagnosis condition is set such that the target rail pressure in the common rail 20 becomes the predetermined pressure PFIN, and the target injection amount instructed to follow the predetermined pressure PFIN becomes the predetermined injection amount QFIN. Thereby, when a certain cylinder satisfies the diagnosis condition, the failure determination is executed after the target rail pressure of all the other cylinders is set to the predetermined pressure PFIN and the target injection amount is controlled to the predetermined injection amount QFIN. . For this reason, when a certain cylinder satisfies the diagnosis condition, the diagnosis opportunity can be increased by adjusting the condition of the other cylinder to that condition.

  In addition, the said embodiment can also be changed and implemented as follows.

  In the above embodiment, it is determined whether or not the quotient obtained by dividing the detected differential pressure ΔPk in one cylinder by the estimated differential pressure ΔPt is within the second predetermined range β. With respect to this, whether the detected differential pressure ΔPk (corresponding to the majority drop) corresponding to the cylinders exceeding the majority is selected, and whether the quotient divided by the detected differential pressure ΔPk and the estimated differential pressure ΔPt is within the second predetermined range β. A determination of whether or not may be performed.

  In the above embodiment, it is determined whether or not the quotient obtained by dividing the detected differential pressure ΔPk by the estimated differential pressure ΔPt is within the second predetermined range β. In this regard, it may be determined whether or not the difference between the detected differential pressure ΔPk and the estimated differential pressure ΔPt is within the fourth predetermined range ω. In this case, the fourth predetermined range ω is set as a range including an error in the difference between the detected differential pressure ΔPk and the estimated differential pressure ΔPt expected when the pressure sensor 22 and the fuel injection valve 40 are normal. That is, when the variation X between the cylinders is within the first predetermined range α and the difference between the detected differential pressure ΔPk and the estimated differential pressure ΔPt is not within the fourth predetermined range ω, a failure of the pressure sensor 22 is determined. .

  Regarding the variation X between cylinders, the standard deviation is defined as the variation X between cylinders using the detected differential pressure ΔPk of each cylinder. In this regard, the dispersion value may be the variation X instead of the standard deviation. In this case, the setting of the first predetermined range α is also changed with the change of the calculation method.

  In the above embodiment, whether or not the quotient obtained by dividing the detected differential pressure ΔPk by the estimated differential pressure ΔPt after determining that the variation X between the cylinders is within the first predetermined range α is within the second predetermined range β. The judgment was carried out. In this regard, when the quotient obtained by dividing the detected differential pressure ΔPk by the estimated differential pressure ΔPt is not within the second predetermined range β, it is determined whether or not the variation X between the cylinders is within the first predetermined range α. May be. In this case, whether or not the quotient obtained by dividing the detected differential pressure ΔPk by the estimated differential pressure ΔPt is within the second predetermined range β is determined for all the cylinders. Referring to FIG. 2, step 105 and step 106 accompanying step 105 and step 107 are interchanged. Specifically, in step 107, it is determined whether or not the quotient obtained by dividing the detected differential pressure ΔPk by the estimated differential pressure ΔPt in all the cylinders is within the second predetermined range β, and the detected differential pressure ΔPk is determined. When there is at least one cylinder whose quotient divided by the estimated differential pressure ΔPt is not within the second predetermined range β (S107: NO), the routine proceeds to step 105. If it is determined in step 105 that the variation X between the cylinders is within the first predetermined range α (step 105: YES), there is a difference between the detected differential pressure ΔPk and the estimated differential pressure ΔPt in all the cylinders. As a result, it is determined that the pressure sensor 22 has failed. On the other hand, when it is determined that the variation X between the cylinders is not within the first predetermined range α (step 105: NO), the routine proceeds to step 106, where it is determined that the fuel injection valve 40 of a certain cylinder has failed. To do.

  When it is determined that the fuel injection valve 40 has failed, the fuel injection valve 40 of the cylinder that shows a value different from the detected differential pressure ΔPk of the cylinder that exceeds a majority is in failure I was going to identify. In this regard, when it is determined that the fuel injection valve 40 is out of order, the fuel injection valve 40 is in a cylinder whose quotient obtained by dividing the detected differential pressure ΔPk by the estimated differential pressure ΔPt is not within the second predetermined range β. You may specify that it is out of order.

  FIG. 7 is a modification of a part of the flowchart of FIG. That is, step 104 in FIG. 2 is deleted, and step 204 is provided instead. In step 204, the detected differential pressure ΔPk that matches the majority of cylinders is selected as the differential pressure ΔPa. Also, step 105 is deleted. Step 107 is deleted, and step 207 is provided instead. In step 207, it is determined whether or not the quotient obtained by dividing the selected differential pressure ΔPa by the estimated differential pressure ΔPt is within the second predetermined range β. When the quotient obtained by dividing the differential pressure ΔPa by the estimated differential pressure ΔPt falls within the second predetermined range β (S207: YES), the process proceeds to step 212, which is newly added. In step 212, it is determined whether or not there is a cylinder whose detected differential pressure ΔPk is not within the third predetermined range γ. At this time, the third predetermined range γ is set as a range including an error in the estimated differential pressure ΔPt. If there is a cylinder whose detected differential pressure ΔPk does not fall within the third predetermined range γ (S212: YES), the routine proceeds to step 206, where it is determined that the fuel injection valve 40 of that cylinder has failed, and this control is performed. finish.

  For the other steps, the processes of steps 200, 201, 202, 203, 208, 209, 210, and 211 in FIG. 7 are respectively performed in steps 100, 101, 102, 103, 108, 109, and 110 of FIG. , And 111 are the same.

  When the pressure sensor 22 is out of order, the detected differential pressure ΔPk of all the cylinders is deviated in a large direction or a small direction with respect to the estimated differential pressure ΔPt expected to be generated by the injection. The quotient obtained by dividing ΔPk by the estimated differential pressure ΔPt is out of the second predetermined range β in all the cylinders. When determining whether such a failure of the pressure sensor 22 has occurred, it is not necessary to determine whether the detected differential pressure ΔPk is deviated from the estimated differential pressure ΔPt in all the fuel injection valves 40. This is because the failure of the fuel injection valve 40 to be determined as a failure by distinction is unlikely to occur in more than a majority of the cylinders at the same time, so that the detected differential pressure ΔPk causes a deviation from the estimated differential pressure ΔPt. This is because it can be determined that the fuel pressure sensor has failed when 40 is greater than the majority. Therefore, the detected differential pressure ΔPk that matches more than a majority from all the calculated detected differential pressures ΔPk is selected as the differential pressure ΔPa, and the quotient obtained by dividing the differential pressure ΔPa by the estimated differential pressure ΔPt is within the second predetermined range β. If not, it is determined that the pressure sensor 22 has failed.

  When the fuel injection valve 40 of a certain cylinder fails, a difference occurs between the detected differential pressure ΔPk and the estimated differential pressure ΔPt when the fuel injection valve 40 fails. For this reason, when the failed fuel injection valve 40 performs fuel injection, the detected differential pressure ΔPk deviates from the third predetermined range γ set as a range including an error in the estimated differential pressure ΔPt. Therefore, when there is a fuel injection valve 40 in which the quotient obtained by dividing the differential pressure ΔPa by the estimated differential pressure ΔPt is within the second predetermined range β and the calculated detected differential pressure ΔPk is outside the third predetermined range γ, It is determined that the fuel injection valve 40 of that cylinder has failed.

  Therefore, it is possible to diagnose the failure of the pressure sensor 22 after determining that the output abnormality of the pressure sensor 22 has not occurred. Further, when it is determined that the fuel injection valve 40 has failed, it is possible to identify which cylinder of the fuel injection valve 40 has failed.

  In this example, it was determined whether or not the quotient obtained by dividing the differential pressure ΔPa by the estimated differential pressure ΔPt falls within the second predetermined range β. In this regard, it may be determined whether or not the difference between the differential pressure ΔPa and the estimated differential pressure ΔPt falls within the fourth predetermined range ω. That is, when the difference between the differential pressure ΔPa and the estimated differential pressure ΔPt does not fall within the fourth predetermined range ω (S207: NO), it is determined that the pressure sensor 22 has failed.

  Whether or not there is a cylinder in which the detected differential pressure ΔPk does not fall within the third predetermined range γ when the quotient obtained by dividing the differential pressure ΔPa by the estimated differential pressure ΔPt does not fall within the second predetermined range β. It was judged. In this regard, if there is a cylinder where the detected differential pressure ΔPk does not fall within the third predetermined range γ by replacing Step 207 and Step 212, the quotient obtained by dividing the differential pressure ΔPa by the estimated differential pressure ΔPt is the second predetermined range β It may be determined whether or not it falls within. Specifically, after step 204 ends, the process proceeds to step 212. If there is a cylinder whose detected differential pressure ΔPk does not fall within the third predetermined range γ (S212: YES), the process proceeds to step 207. If the quotient obtained by dividing the differential pressure ΔPa by the estimated differential pressure ΔPt falls within the second predetermined range β (S207: YES), the routine proceeds to step 206, where it is determined that the fuel injection valve 40 has failed. When the quotient obtained by dividing the differential pressure ΔPa by the estimated differential pressure ΔPt does not fall within the second predetermined range β (S207: NO), the process proceeds to step 208, and it is determined that the pressure sensor 22 has failed.

DESCRIPTION OF SYMBOLS 10 ... Fuel injection system, 16 ... Fuel supply pump, 20 ... Common rail, 22 ... Pressure sensor, 40 ... Fuel injection valve, 50 ... ECU.

Claims (8)

An accumulator (20) for storing high-pressure fuel;
A fuel pump (16) for pressurizing and discharging the fuel to be supplied to the pressure accumulation chamber;
A plurality of fuel injection valves (40) for injecting fuel stored in a high pressure state in the pressure accumulation chamber;
A fuel pressure sensor (22) for detecting the fuel pressure in the pressure accumulation chamber;
A failure diagnosis device (50) applied to a fuel injection system (10) comprising:
When the fuel is injected under a predetermined injection condition by one of the plurality of fuel injectors, the remaining fuel injectors execute the fuel injection under the predetermined injection condition. Means,
A detected drop amount calculating means for calculating a drop amount of the fuel pressure in the pressure accumulating chamber caused by the injection by the fuel injection valve under the predetermined injection condition as a detected drop amount, respectively, based on a detection value of the fuel pressure sensor;
Estimated drop amount calculating means for calculating a drop amount of the fuel pressure in the pressure accumulating chamber, which is estimated to be caused by the injection by the fuel injection valve under the predetermined injection conditions,
Variation calculating means for calculating variations among the plurality of fuel injection valves of the detected drop amount calculated by the detected drop amount calculating unit;
The difference calculated by the variation calculating means is within a first predetermined range, and the difference between the detected drop calculated by the detected drop calculating means and the estimated drop calculated by the estimated drop calculating means A fuel pressure sensor failure determination means for determining a failure of the fuel pressure sensor when the amount is out of the second predetermined range;
A failure diagnosis apparatus for a fuel injection system, comprising: Feedback control means for controlling a feedback amount of a discharge amount of fuel discharged by the fuel pump so that the fuel pressure detected by the fuel pressure sensor is set as a target pressure;
Feedback amount determination means for determining whether the feedback amount controlled by the feedback control means is large or small with respect to the initial value of the feedback amount corresponding to the target pressure;
When the fuel pressure sensor failure determination means determines that the fuel pressure sensor has failed, the direction of deviation of the output of the fuel pressure sensor relative to the actual fuel pressure in the pressure accumulating chamber is specified based on the result of the feedback amount determination means. A deviation direction specifying means;
The failure diagnosis device for a fuel injection system according to claim 1, comprising: A fuel injection valve failure determination unit that determines that the fuel injection valve has failed when the variation calculated by the variation calculation unit is out of a first predetermined range;
3. The fuel pressure sensor failure is determined by the fuel pressure sensor failure determination means when the fuel injection valve failure determination means does not determine that the fuel injection valve has failed. The fuel pressure sensor failure is determined by the fuel pressure sensor failure determination means. Diagnostic device for fuel injection system.   When the fuel injection valve failure determination means determines that the fuel injection valve has failed, the detected drop amount calculated by the detected drop amount calculation means is compared between the cylinders, and the detected drop amount exceeds a majority. The failure diagnosis of the fuel injection system according to claim 3, further comprising: a failure injection valve specifying unit that specifies that the fuel injection valve of the cylinder has a failure with respect to a cylinder different from the detected drop amount. apparatus.   The fuel pressure sensor failure determination means determines the detected drop amount that is greater than a majority from the detected drop amount calculated by the detected drop amount calculator and the variation calculated by the variation calculator is within a first predetermined range. 5. The fuel pressure sensor is determined to be a failure when the majority drop amount is selected and a difference between the majority drop amount and the estimated drop amount is out of a second predetermined range. 2. A failure diagnosis apparatus for a fuel injection system according to claim 1. An accumulator (20) for storing high-pressure fuel;
A fuel pump (16) for pressurizing and discharging the fuel to be supplied to the pressure accumulation chamber;
A plurality of fuel injection valves (40) for injecting fuel stored in a high pressure state in the pressure accumulation chamber;
A fuel pressure sensor (22) for detecting the fuel pressure in the pressure accumulation chamber;
A failure diagnosis device (50) applied to a fuel injection system (10) comprising:
When the fuel is injected under a predetermined injection condition by one of the plurality of fuel injectors, the remaining fuel injectors execute the fuel injection under the predetermined injection condition. Means,
A detected drop amount calculating means for calculating a drop amount of the fuel pressure in the pressure accumulating chamber caused by the injection by the fuel injection valve under the predetermined injection condition as a detected drop amount, respectively, based on a detection value of the fuel pressure sensor;
Estimated drop amount calculating means for calculating a drop amount of the fuel pressure in the pressure accumulating chamber, which is estimated to be caused by the injection by the fuel injection valve under the predetermined injection conditions,
The detected drop amount exceeding a majority is selected as a majority drop amount from the detected drop amount for each cylinder calculated by the detected drop amount calculating means, and the estimated drop amount calculated by the majority drop amount and the estimated drop amount calculating means. A difference amount calculating means for calculating a difference amount based on the difference from the descent amount;
A fuel pressure sensor failure determination unit that determines that the fuel pressure sensor has failed when the difference amount calculated by the difference amount calculation unit is out of a second predetermined range;
A failure diagnosis apparatus for a fuel injection system, comprising: The fuel pressure sensor failure determining means does not determine that the fuel pressure sensor has failed, and there is the fuel injection valve in which the detected drop amount calculated by the detected drop amount calculating means is outside a third predetermined range, A fuel injection valve failure determination means for determining a failure of the fuel injection valve;
A failure diagnosis apparatus for a fuel injection system according to claim 6.   The predetermined injection condition is characterized in that a target pressure in the pressure accumulating chamber is determined as a predetermined pressure, and an instructed injection amount instructed by the injection execution means is set to a predetermined injection amount in accordance with the predetermined pressure. The failure diagnosis device for a fuel injection system according to any one of claims 1 to 7.