JP2011099343A - Failure diagnostic device of fuel pressure sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a failure diagnostic device of a fuel pressure sensor capable of detecting the failure of the fuel pressure sensor more adequately. <P>SOLUTION: An ECU 10 estimates a rail pressure of a common rail 3, and also determines the existence of failure of the fuel pressure sensor 8 based on comparison of a trajectory length of the transition curve of the detected values of fuel pressure sensor 8 at the transient operation of an engine and the trajectory length of the transition curve of an estimated value of rail pressure at the same transient operation. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an abnormality diagnosis device for a fuel pressure sensor that is provided in an engine fuel system and detects an abnormality of a fuel pressure sensor that detects a fuel pressure.

  In a diesel engine that employs a common rail system, fuel is supplied into a cylinder by injecting fuel accumulated in a common rail, which is a pressure accumulating vessel, from an injector based on an injection command signal. In such a common rail system, a fuel pressure in the common rail, that is, a so-called rail pressure is detected by a fuel pressure sensor, and the injection period is adjusted based on the detection result, thereby finely controlling the fuel injection amount. Further, in the common rail system, the rail pressure is controlled to an appropriate pressure by feedback-controlling the operation of the supply pump so that the detection value of the rail pressure sensor approaches the target value.

  On the other hand, conventionally, as seen in Patent Document 1, there has been proposed an injection abnormality detection device for detecting an injection abnormality of an injector based on a transition waveform of a fuel pressure detected by a fuel pressure sensor provided in the injector. Yes. In this detector, a sensor for detecting the fuel pressure inside the injector is provided in the injector, and a transition waveform of the fuel pressure detected by the sensor is compared with an assumed transition waveform, and a significant difference is recognized between the two. Sometimes, it is determined that an injection abnormality has occurred due to clogging of the injection hole, poor sliding of the needle valve, or the like. It should be noted that the trajectory length of the transition curve of the fuel pressure detection value and its time integral value are used to determine whether there is an abnormality at this time.

JP 2009-85164 A

  By the way, in the common rail system as described above, the detection result of the fuel pressure (rail pressure) is used for the control of the injector and the fuel pump, and when the fuel pressure sensor becomes abnormal and a correct detection value cannot be obtained, The required pressure and the actual pressure may deviate, which may cause inconveniences such as drivability deterioration and emission deterioration. Therefore, it is important to monitor the behavior of the fuel pressure sensor and check whether there is any abnormality.

  As a conventional fuel pressure sensor abnormality diagnosis method, for example, a method for detecting an abnormality in the following manner has been proposed. That is, in the prior art, a fuel pressure detection system is configured as a dual system in which two fuel pressure sensors and two circuits thereof are installed, and whether or not there is a significant difference between the detected values of the fuel pressure. Depending on the situation, an abnormality diagnosis of the fuel pressure sensor is performed. In such a case, an abnormality of the fuel pressure sensor can surely be detected. However, two sets of sensors and their circuits are required, which increases the manufacturing cost. In addition, even if there is a difference between the detection values of both sensors, it is impossible to determine until one of the sensors has failed, only by knowing that one of the sensors has failed. Therefore, if one of the two sensors breaks down, normal operation cannot be performed at that time, and the reliability of the fuel pressure detection system is lowered.

  These problems are not limited to diesel engines that employ a common rail system, but are common to all engines that use a fuel pressure sensor to detect the fuel pressure in the accumulator vessel.

  The present invention has been made in view of such circumstances, and a problem to be solved is to provide a fuel pressure sensor abnormality diagnosis device capable of more accurately detecting abnormality of the fuel pressure sensor. .

  In order to solve the above-mentioned problem, the invention of claim 1 as an abnormality diagnosis device for a fuel pressure sensor for diagnosing abnormality of a fuel pressure sensor for detecting a fuel pressure of an accumulator vessel provided in a fuel system of an engine Based on the comparison between the estimation means for estimating the fuel pressure, the degree of change in the detected value of the fuel pressure sensor during the transient operation of the engine, and the degree of change in the estimated value of the fuel pressure by the estimation means during the transient operation Judgment means for judging the presence or absence of abnormality of the pressure sensor is provided.

  The fuel pressure in the pressure accumulator can be estimated with a certain degree of accuracy based on the amount of fuel leakage from the pressure accumulator, the amount of fuel pumped into the pressure accumulator, the amount of fuel injection, and the like. However, the fuel pressure in the pressure accumulating vessel varies greatly depending on differences in the clearance of fuel system components such as a fuel pump, and individual differences and changes over time are large. Therefore, it is difficult to estimate with high accuracy. Therefore, even if there is no abnormality in the fuel pressure sensor, the detected value may deviate greatly from the estimated value of the accumulator fuel pressure, and simply comparing the detected value and estimated value of the accumulator fuel pressure It is difficult to determine whether the pressure sensor is abnormal.

  On the other hand, if the fuel pressure sensor is normal, during the transient operation in which the fuel pressure in the pressure accumulator changes greatly, the sensor detection value also changes greatly following the actual change in fuel pressure. On the other hand, if there is an abnormality in the fuel pressure sensor, the change in the sensor detection value following the actual change in the fuel pressure does not appear clearly. Therefore, it is possible to easily and accurately confirm whether there is an abnormality in the fuel pressure sensor by looking at the degree of change in the detected value of the fuel pressure sensor during the transient operation of the engine.

  In that respect, in the above configuration, the fuel pressure sensor is based on a comparison between the degree of change in the detected value of the fuel pressure sensor during the transient operation of the engine and the degree of change in the estimated value of the fuel pressure by the estimating means during the transient operation. A determination unit is configured to determine whether there is an abnormality. Therefore, it is possible to detect the abnormality of the fuel pressure sensor more accurately.

  As an index value of the degree of change used by the determination means for the determination, the trajectory length of the fuel pressure transition curve can be used as in claim 2. As the index value, it is also possible to use the time area of the fuel pressure transition curve as in claim 3.

  Even if there is no abnormality in the fuel pressure sensor, there may be a relatively large difference between the degree of change in the detected value and the degree of change in the estimated value of the pressure accumulator fuel pressure temporarily. Therefore, if it is desired to perform an abnormality diagnosis more accurately, it is preferable that the determination means is configured to determine whether there is an abnormality based on the integrated value of the index values in a prescribed determination period as in claim 4. .

  However, in order to ensure the accuracy of diagnosis, if a long time is set as the determination period, the response to an instantaneous failure leading to a burst or the like may be delayed. In order to cope with such an instantaneous failure, as described in claim 5, when the deviation between the index value of the change degree of the detected value and the index value of the change degree of the estimated value becomes excessive, it is immediately determined that there is an abnormality at that time. The determination means may be configured to perform the determination.

  In addition, if the determination period is set to be long in order to ensure the accuracy of the diagnosis, the diagnosis can be performed only when the transient operation is continuously continued for a long time, and the opportunity for diagnosis is reduced. Therefore, according to the sixth aspect of the present invention, the presence or absence of abnormality is determined by comparing the detected value and the estimated value when the engine is in a transient operation state for a predetermined determination period. When the duration of continuous transient operation is performed intermittently and does not reach the determination period, an abnormality diagnosis is performed using the sum of the fragment values of the index value of the degree of change during the period in which transient operation is established If the determination means is configured as described above, diagnosis can be performed even if the transient operation is not continued continuously for a long time, and the opportunities for diagnosis can be increased.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic which shows typically the structure of the fuel system of the engine used as the application object about 1st Embodiment of the abnormality diagnosis apparatus of the fuel pressure sensor of this invention. The graph which shows transition of the sensor pressure detection value of a rail pressure estimated value, a normal fuel pressure sensor, and an abnormal fuel pressure sensor, respectively. The graph which shows the calculation aspect of the locus | trajectory length in the embodiment. 6 is a flowchart showing a processing procedure of an engine control unit in an abnormality diagnosis routine of a fuel pressure sensor adopted by the embodiment. The graph which shows the calculation aspect of the time area in 3rd Embodiment of the abnormality diagnosis apparatus of the fuel pressure sensor of this invention. 6 is a flowchart showing a processing procedure of an engine control unit in an abnormality diagnosis routine of a fuel pressure sensor adopted by the embodiment. The graph which shows the normality and abnormality determination range of the fuel pressure sensor in 4th Embodiment of the abnormality diagnosis apparatus of the fuel pressure sensor of this invention.

(First embodiment)
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment that embodies an abnormality diagnosis device for a fuel pressure sensor according to the present invention will be described below in detail with reference to FIGS.

  FIG. 1 shows the configuration of a fuel system of an internal combustion engine to which the present embodiment is applied. The abnormality diagnosis device for a fuel pressure sensor according to the present embodiment is applied to a common rail type diesel engine.

  As shown in the figure, a fuel pump of this diesel engine is provided with a supply pump 2 that pumps fuel from a fuel tank 1 and pressurizes and discharges the fuel. The supply pump 2 supplies high-pressure fuel to the common rail 3 that is a pressure accumulating container. The supply pump 2 also supplies high-pressure fuel to a fuel addition valve 4 that adds fuel to the exhaust system.

  The common rail 3 is connected to an injector 5 for each cylinder of the diesel engine. Further, the common rail 3 is provided with a pressure reducing valve 7 for setting the fuel pressure (rail pressure) in the common rail 3 to a certain value or less, and a fuel pressure sensor 8 for detecting the rail pressure.

  The injector 5 is connected to the fuel tank 1 through a check valve 9, and excess fuel is returned to the fuel tank 1 through the check valve 9. The injector 5 is connected to the supply pump 2 via a feed valve 6, and fuel is directly supplied from the supply pump 2 via the feed valve 6 when the engine is started.

  A diesel engine having such a fuel system is controlled by an electronic control unit (ECU) 10. The ECU 10 is configured as a computer unit including a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output port (I / O). Here, the CPU performs various arithmetic processes related to engine control, and the ROM stores programs and data used for engine control. The RAM temporarily stores the calculation results of the CPU, the detection results of the sensors, etc., and the I / O mediates exchange of signals with the outside. In addition to the rail pressure detected by the fuel pressure sensor 8, detection results such as the engine speed, the accelerator operation amount, the intake air amount, the exhaust pressure, and the intake pressure are input to the ECU 10.

  In the abnormality diagnosis device of the present embodiment, the ECU 10 controls the operation of the supply pump 2 as a part of engine control so as to ensure the necessary rail pressure based on the detection result of the fuel pressure sensor 8 and the like. Yes. Further, the ECU 10 controls the fuel injection of the injector 5 by outputting a command signal to the drive circuit (EDU) 11.

  In the present embodiment configured as described above, the ECU 10 performs abnormality diagnosis control of the fuel pressure sensor 8. Details of the abnormality diagnosis control of the fuel pressure sensor 8 in the present embodiment will be described below.

  As a method for diagnosing abnormality of the fuel pressure sensor 8, it is conceivable to perform abnormality diagnosis by estimating the rail pressure from the operating condition of the fuel system and comparing the estimated value with the detected value of the fuel pressure sensor 8. That is, the amount of fuel leakage from the common rail 3, the amount of fuel pumped from the supply pump 2 to the common rail 3, the amount of fuel supplied from the common rail 3 to the injector 5 and the like are obtained, and the rail pressure is estimated from the obtained values. To do. If the detected value of the fuel pressure sensor 8 deviates greatly from the value estimated from the current operating status of the fuel system, the current sensor detected value indicates an inappropriate value, and the fuel pressure sensor 8 can be diagnosed as having an abnormality.

  However, these diagnostic methods have the following problems. That is, the fuel leak amount and the fuel pumping amount of the fuel system are greatly influenced by a subtle difference in the clearances of the fuel system components such as the supply pump 2. For this reason, there are large individual differences and changes over time in the amount of fuel leak and the amount of fuel pumped in the fuel system. Therefore, the rail pressure of the common rail 3 cannot be estimated with very high accuracy. Therefore, as shown in FIG. 2, even if there is no abnormality in the fuel pressure sensor 8, the detected value and the estimated value may greatly deviate, and the detected value of the rail pressure and the estimated value are simply compared. Thus, it is difficult to determine whether the fuel pressure sensor 8 is abnormal.

  On the other hand, as shown in FIG. 2, during the transient operation in which the rail pressure changes greatly, if the fuel pressure sensor 8 is normal, the sensor detection value also changes greatly following the change in the actual rail pressure. . On the other hand, if there is an abnormality in the fuel pressure sensor 8, a clear change in the sensor detection value following the actual change in rail pressure will not appear. Therefore, it is possible to easily and accurately confirm whether there is an abnormality in the fuel pressure sensor 8 by looking at the degree of change in the detected value of the fuel pressure sensor 8 during the transient operation of the engine.

  Therefore, in the present embodiment, the ECU 10 estimates the rail pressure, and calculates the change degree of the detected value of the fuel pressure sensor 8 during the transient operation of the engine and the change degree of the rail pressure estimation value during the transient operation. Based on the comparison, the presence or absence of abnormality of the fuel pressure sensor 8 is determined.

  Incidentally, in this embodiment, the rail pressure estimated value P (i) is calculated using the following equation (1). “InjQ” in the following equation (1) is the volume of fuel used for fuel injection in the injector 5, “Leak Q” is the volume of fuel leaking from the common rail 3, and “PumpQ” is the supply pump 2 The volume of the fuel supplied from each is shown. “High pressure section volume” indicates the volume of the common rail 3, and “P (i−1)” indicates the calculated value of the estimated rail pressure value in the previous calculation cycle.

なお、本実施の形態では、こうした異常の有無の判定に使用するセンサー検出値やレール圧推定値の変化度合いの指標値として、センサー検出値及びレール圧推定値の推移曲線の軌跡長を用いるようにしている。ここでは、そうした推移曲線の軌跡長の演算を規定の演算周期（例えば８０ミリ秒）毎に行うようにしている。

In the present embodiment, the trajectory length of the transition curve of the sensor detection value and the estimated rail pressure value is used as an index value for the degree of change in the detected sensor value and the estimated rail pressure value used to determine the presence or absence of such an abnormality. I have to. Here, the calculation of the trajectory length of the transition curve is performed every prescribed calculation cycle (for example, 80 milliseconds).

  The calculation of the locus length of the transition curve in the present embodiment is performed using the following equation (2). That is, the trajectory length is the sum of the square value of the difference between the sensor detection value or the estimated value of rail pressure pi-1 in the previous calculation cycle and the same value pi in the current calculation cycle and the square value of the calculation cycle. Calculated as the square root.

そして本実施の形態では、ＥＣＵ１０は、規定の判定期間（例えば２０秒程度）におけるセンサー検出値の軌跡長Ａの積算値とレール圧推定値の軌跡長Ｂの積算値とを求め、それら積算値の比に基づいて燃料圧力センサー８の異常の有無を判定している。すなわち、図３に示すように、ＥＣＵ１０は、各演算周期において求められたセンサー検出値の軌跡長の値Ｌａ_1，Ｌａ_2，…，Ｌａ_nの判定期間における積算値と、各演算周期において求められたレール圧推定値の軌跡長の値Ｌｂ_1，Ｌｂ_2，…，Ｌｂ_nの判定期間における積算値とをそれぞれ求めるようにしている。そしてＥＣＵ１０は、それら積算値の比を求め、その比が規定の正常範囲、例えば０．８から１．２の範囲にあれば、正常と判定し、その範囲外にあれば、異常と判定するようにしている。

In the present embodiment, the ECU 10 obtains the integrated value of the trajectory length A of the sensor detection value and the integrated value of the trajectory length B of the estimated rail pressure value in a specified determination period (for example, about 20 seconds), and these integrated values. Based on this ratio, the presence or absence of abnormality of the fuel pressure sensor 8 is determined. That is, as shown in FIG. 3, the ECU 10 determines the integrated value in the determination period of the trajectory length values La_1, La_2,..., La_n of the sensor detection values obtained in each calculation cycle and the rails obtained in each calculation cycle. The integrated values in the determination period of the pressure length estimated value Lb_1, Lb_2,..., Lb_n are obtained. Then, the ECU 10 obtains a ratio of the integrated values, and determines that the ratio is normal if the ratio is within a specified normal range, for example, a range of 0.8 to 1.2. I am doing so.

  FIG. 4 shows a flowchart of an abnormality diagnosis routine of the fuel pressure sensor 8 employed in this embodiment. The processing of this routine is performed by the ECU 10 every calculation period of the locus length during engine operation.

  When this routine is started, the ECU 10 first checks in step S100 whether an abnormality diagnosis condition is satisfied. In this abnormality diagnosis condition, a condition that is a precondition for abnormality diagnosis of the fuel pressure sensor 8 is set. For example, the warm-up of the engine is completed, and other than the fuel pressure sensor 8 used for diagnosis There are no abnormalities in the sensor. If the abnormality diagnosis condition is not satisfied (S100: NO), the ECU 10 proceeds to step S102, where both the sensor detection value and the integrated value of the track length of the rail pressure estimation value are cleared (reset to “0”). Then, the process of this routine is finished.

  On the other hand, if the abnormality diagnosis condition is satisfied (S100: YES), the ECU 10 proceeds to step S101, and confirms in step S101 whether the vehicle is in a transient operation state. Here, the determination as to whether or not the operation is a transient operation is performed based on whether or not any of the engine speed, the accelerator operation amount, the intake air amount, the exhaust pressure, and the intake pressure has changed by a certain value or more. If the ECU 10 is not in the transient operation state (S101: NO), the ECU 10 proceeds to step S102, where both the sensor detection value and the integrated value of the trajectory length of the rail pressure estimation value are cleared (reset to “0”). Then, the process of this routine is finished.

  On the other hand, if it is a transient operation state (S101: YES), the ECU 10 proceeds to step S103, and in step S103, the locus length A of the transition curve of the sensor detection value in the period from the previous calculation cycle to the current calculation cycle. Is calculated. In step S104, the ECU 10 calculates the trajectory length B of the transition curve of the estimated rail pressure value during the period from the previous calculation cycle to the current calculation cycle. In step S105, the ECU 10 calculates the integrated values of the trajectory lengths A and B, respectively. The calculation of the integrated value at this time is performed by adding the locus lengths A and B calculated this time to the previous value of the integrated value.

  After calculating the integrated values of the trajectory lengths A and B in this way, the ECU 10 confirms whether or not the determination period has elapsed in step S106, that is, whether or not the integrated period of the trajectory lengths A and B has exceeded the determination period. To do. If the determination period has not elapsed (S106: NO), the ECU 10 ends the processing of this routine as it is.

  On the other hand, if the determination period has elapsed (S106: YES), the ECU 10 proceeds to step S107. In step S107, the integrated value of the track length A of the sensor detection value and the track length B of the rail pressure estimation value are determined. Check if the ratio to the integrated value is within the specified normal range. If the ratio is within the normal range (S107: YES), the ECU 10 makes a normal determination in step S108 and completes the current abnormality diagnosis. If the ratio is not within the normal range (S107: NO), the ECU 10 makes an abnormality determination in step S109 and completes the current abnormality diagnosis.

In this embodiment, the ECU 10 corresponds to the estimation unit and the determination unit.
According to the fuel pressure sensor abnormality diagnosis device of the present embodiment described above, the following effects can be obtained.

  (1) In the present embodiment, the ECU 10 estimates the rail pressure, and also calculates the trajectory length of the sensor detection value transition curve during the transient operation of the engine and the transition curve of the rail pressure estimation value during the transient operation. The presence / absence of abnormality of the fuel pressure sensor 8 is determined based on the comparison with the locus length. Even if the estimation accuracy of the rail pressure estimation value is low, an accurate abnormality diagnosis of the fuel pressure sensor 8 can be performed by comparing the change tendency of the sensor detection value and the rail pressure estimation value during transient operation. In this regard, in the present embodiment, the trajectory length of the transition curve of the sensor detection value and the estimated rail pressure value is used as an index value of the degree of change, and abnormality diagnosis is performed by comparing the integrated values during the transient operation. Therefore, according to the present embodiment, the abnormality of the fuel pressure sensor 8 can be detected more accurately.

(Second Embodiment)
Next, a second embodiment of the fuel pressure sensor abnormality diagnosis device of the present invention will be described. In the present embodiment, elements common to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the first embodiment, since a relatively long time is set in the determination period, the response to an instantaneous failure that leads to a burst or the like may be delayed. Therefore, in this embodiment, when the deviation between the trajectory length of the sensor detection value transition curve and the trajectory length of the rail pressure estimated value transition curve becomes excessive, it is immediately determined that there is an abnormality at that time. ing. Specifically, the ECU 10 obtains the integrated value of the sensor detection value and the track length of the rail pressure estimation value in a shorter period (for example, 1 second) than the determination period. When the ratio of the integrated values deviates from a normal range, for example, a range from 0.3 to 1.7, the ECU 10 immediately performs abnormality determination.

  According to the present embodiment, when the deviation between the trajectory length of the sensor detection value transition curve and the trajectory length of the rail pressure estimated value transition curve is excessive, the abnormality determination is performed without waiting for the completion of the determination period. Since it can be performed, it becomes possible to cope with an instantaneous failure that leads to a burst or the like.

(Third embodiment)
Next, a third embodiment of the fuel pressure sensor abnormality diagnosis device of the present invention will be described. Note that in this embodiment, elements that are the same as those in the above embodiment are given the same reference numerals, and detailed descriptions thereof are omitted.

  In the above embodiment, the trajectory length of the transition curve of these values is used as the index value of the change degree of the sensor detection value and the estimated rail pressure value. In the present embodiment, the time area of the transition curve of the sensor detection value and the estimated rail pressure value is used as such an index value.

  The calculation of the time area in the present embodiment is performed using the following equation (3). That is, the time area is calculated as a time integral value of the difference between the current sensor detection value or rail pressure value pnow and the value pi-1 at the end of the previous calculation cycle.

そして本実施の形態では、ＥＣＵ１０は、エンジンの過渡運転中における規定の判定期間（例えば２０秒程度）のセンサー検出値の時間面積Ａの積算値とレール圧推定値の時間面積Ｂの積算値とを求め、それら積算値の比に基づいて燃料圧力センサー８の異常の有無を判定している。すなわち、図５に示すように、ＥＣＵ１０は、各演算周期において求められたセンサー検出値の軌跡長の値Ａａ_1，Ａａ_2，…，Ａａ_nの判定期間における積算値と、各演算周期において求められたレール圧推定値の軌跡長の値Ａｂ_1，Ａｂ_2，…，Ａｂ_nの判定期間における積算値とをそれぞれ求めるようにしている。そしてＥＣＵ１０は、それら積算値の比を求め、その比が規定の正常範囲、例えば０．７から１．３の範囲にあれば、正常と判定し、その範囲外にあれば、異常と判定するようにしている。

In the present embodiment, the ECU 10 calculates the integrated value of the time area A of the sensor detection value and the integrated value of the time area B of the estimated rail pressure value during a specified determination period (for example, about 20 seconds) during the transient operation of the engine. And the presence or absence of abnormality of the fuel pressure sensor 8 is determined based on the ratio of the integrated values. That is, as shown in FIG. 5, the ECU 10 determines the integrated value in the determination period of the locus lengths Aa_1, Aa_2,..., Aa_n of the sensor detection values obtained in each calculation cycle, and the rails obtained in each calculation cycle. The estimated values of the trajectory lengths Ab_1, Ab_2,..., Ab_n of the estimated pressure values are obtained in the determination period. Then, the ECU 10 obtains a ratio of these integrated values, and determines that the ratio is normal if the ratio is within a specified normal range, for example, a range of 0.7 to 1.3. I am doing so.

  FIG. 6 shows a flowchart of an abnormality diagnosis routine for the fuel pressure sensor 8 employed in this embodiment. The processing of this routine is performed by the ECU 10 every calculation period of the locus length during engine operation.

  When this routine is started, the ECU 10 first checks in step S200 whether an abnormality diagnosis condition is satisfied. In this abnormality diagnosis condition, a precondition for abnormality diagnosis of the fuel pressure sensor 8 is set. For example, the warm-up of the engine is completed, and sensors other than the fuel pressure sensor 8 used for diagnosis are included. There are no abnormalities. Here, if the abnormality diagnosis condition is not satisfied (S200: NO), the ECU 10 proceeds to step S202, and in step S202, both the sensor detection value and the integrated value of the time area of the rail pressure estimation value are cleared (reset to “0”). Then, the process of this routine is finished.

  On the other hand, if the abnormality diagnosis condition is satisfied (S200: YES), the ECU 10 proceeds to step S201, and confirms whether or not it is in a transient operation state in step S201. Here, the determination as to whether or not the operation is a transient operation is performed based on whether or not any of the engine speed, the accelerator operation amount, the intake air amount, the exhaust pressure, and the intake pressure has changed by a certain value or more. If it is not in the transient operation state (S201: NO), the ECU 10 clears both the integrated value of the time area of the sensor detection value and the estimated rail pressure value (reset to “0”) in step S202, and this time The routine processing ends.

  On the other hand, if it is in the transient operation state (S201: YES), the ECU 10 proceeds to step S203, and in step S203, the time area A of the transition curve of the sensor detection value in the period from the previous calculation cycle to the current calculation cycle. Is calculated. In step S204, the ECU 10 calculates the time area B of the transition curve of the estimated rail pressure value during the period from the previous calculation cycle to the current calculation cycle. In step S205, the ECU 10 calculates the integrated values of the time areas A and B, respectively. The calculation of the integrated value at this time is performed by adding the time areas A and B calculated this time to the previous value of the integrated value.

  After calculating the integrated values of the time areas A and B in this manner, the ECU 10 confirms in step S206 whether or not the determination period has elapsed, that is, whether or not the integrated period of the time areas A and B has exceeded the determination period. To do. If the determination period has not elapsed (S206: NO), the ECU 10 ends the processing of this routine as it is.

  On the other hand, if the determination period has elapsed (S206: YES), the ECU 10 proceeds to step S207, and in step S207, the integrated value of the time area A of the sensor detection value and the time area B of the rail pressure estimation value. Check if the ratio to the integrated value is within the specified normal range. If the ratio is within the normal range (S207: YES), the ECU 10 makes a normal determination in step S208 and completes the current abnormality diagnosis. If the ratio is not within the normal range (S207: NO), the ECU 10 performs abnormality determination in step S209 and completes the current abnormality diagnosis.

Also according to the present embodiment described above, it is possible to detect the abnormality of the fuel pressure sensor 8 more accurately as in the first embodiment.
In this embodiment, since a relatively long time is set for the determination period, the response to an instantaneous failure that leads to a burst or the like may be delayed. If you want to deal with such an instantaneous failure, if the deviation between the time area of the transition curve of the sensor detection value and the time area of the transition curve of the rail pressure estimation value becomes excessive, immediately determine that there is an abnormality at that point. Like to do. Specifically, an integrated value of the time areas of the sensor detection value and the estimated rail pressure value in a shorter period (for example, 1 second) than the determination period is obtained, and the ratio of these integrated values is within a normal range, for example, 0. When the value deviates from the range of 2 to 1.9, the abnormality is determined immediately at that time. In such a case, when the deviation between the time area of the transition curve of the sensor detection value and the time area of the transition curve of the rail pressure estimation value becomes excessive, it is possible to perform the abnormality determination without waiting for the completion of the determination period. This makes it possible to quickly respond to instantaneous failures that lead to bursts and the like.

(Fourth embodiment)
Next, a description will be given of a fourth embodiment that embodies the abnormality diagnosis device for a fuel pressure sensor according to the present invention. Note that in this embodiment, elements that are the same as those in the above embodiment are given the same reference numerals, and detailed descriptions thereof are omitted.

  In the first and second embodiments, abnormality diagnosis of the fuel pressure sensor 8 is performed using the locus length of the transition curve of the sensor detection value and the estimated rail pressure value. In the third embodiment, the abnormality diagnosis of the fuel pressure sensor 8 is performed using the time area of the transition curve of the sensor detection value and the estimated rail pressure value. On the other hand, in the present embodiment, abnormality diagnosis of the fuel pressure sensor 8 is performed using both the locus length and the time area.

  In the present embodiment, during the transient operation of the engine, the ECU 10 obtains the integrated value of the track length of the sensor detection value and the integrated value of the track length of the estimated rail pressure value during a specified determination period (for example, about 20 seconds). I have to. In parallel with this, the ECU 10 obtains the integrated value of the time area of the sensor detection value and the integrated value of the time area of the estimated rail pressure value in the prescribed determination period. After the determination period ends, the ECU 10 determines the ratio (trajectory length ratio) between the integrated value of the track length of the sensor detection value and the integrated value of the track length of the rail pressure estimation value, and the integrated value of the time area of the sensor detection value. A ratio (time area ratio) of the estimated rail pressure value to the integrated value of the time area is calculated, and normality / abnormality of the fuel pressure sensor 8 is determined based on the ratio.

  FIG. 7 shows a normal / abnormal determination range of the fuel pressure sensor 8 in the present embodiment. When the coordinate point on FIG. 7 indicated by the locus length ratio and the time area ratio calculated at the time of this abnormality diagnosis is in the region r1 shown in FIG. 7, it is determined that the fuel pressure sensor 8 is normal. . Further, when the coordinate point on FIG. 7 indicated by the trajectory length ratio and the time area ratio calculated in this abnormality diagnosis is in the region r2 shown in FIG. 7, it is determined that the fuel pressure sensor 8 is abnormal. The On the other hand, when the coordinate point on FIG. 7 indicated by the locus length ratio and the time area ratio in a period shorter than the determination period (for example, 1 second) is in the region r3 shown in FIG. The fuel pressure sensor 8 is determined to be abnormal.

In this embodiment, the accuracy of abnormality diagnosis can be further increased. In addition, the time for abnormality diagnosis can be shortened.
(Fifth embodiment)
In each of the above embodiments, a relatively long time (about 20 seconds) is set as the determination period. Therefore, the diagnosis can be completed only when the transient operation is continued continuously for a long time, and the diagnosis opportunity is naturally limited. Therefore, in the present embodiment, the abnormality diagnosis can be performed even when the transient operation of the engine is intermittently performed and the duration of the continuous transient operation is less than the determination period.

  In other words, in the present embodiment, the sensor detection value and the rail pressure estimated value during the period in which the transient operation is established, the trajectory length of the transition curve and the fragment value of the time area are obtained, and the sum of the fragment values is used for abnormality. The diagnosis is carried out. The fragment value here is an integrated value of the trajectory length or time area in the establishment period of the transient operation. If the abnormality diagnosis is performed using the total of the fragment values for the determination period, the diagnosis can be performed even if the transient operation is not continuously continued during the determination period. Therefore, according to the present embodiment, it is possible to increase the chances of diagnosis.

The above-described embodiments can be implemented with the following modifications.
In the first and second embodiments, the above-described equation (2) is used to calculate the locus length of the sensor detection value and the rail pressure estimation value. It is also possible to perform the calculation. For example, the trajectory length can be calculated by performing time integration of the change amount of the sensor detection value and the estimated rail pressure value.

  In the third embodiment, the time area of the sensor detection value and the rail pressure estimation value is calculated using the above equation (3), but the calculation is performed using a different mathematical formula. It is also possible to do this. For example, the time area can be calculated by performing time integration of the sensor detection value and the estimated rail pressure value.

  In the above embodiment, it is determined that the engine is in transient operation on the condition that any of engine speed, accelerator operation amount, intake air amount, exhaust pressure, and intake pressure changes by a certain value or more. It was. The determination conditions for such transient operation are not limited to this, and may be changed as appropriate.

  In the above embodiment, the abnormality diagnosis of the fuel pressure sensor 8 is performed using the trajectory length or time area of the transition curve as an index value of the degree of change in the sensor detection value and the estimated rail pressure value. However, if the parameter indicates the degree of change in the sensor detection value or rail pressure estimation value, such as the amount of change per unit time in the sensor detection value or rail pressure estimation value, abnormality diagnosis is performed using that parameter as the index value. It is also possible to do this.

  In the above embodiment, the case where the present invention is implemented for a fuel pressure sensor that detects the rail pressure of a common rail diesel engine has been described. However, the abnormality diagnosis device of the present invention is provided in an engine other than the diesel engine. It can also be applied to a fuel pressure sensor. In short, as long as the fuel pressure sensor detects the fuel pressure in the pressure accumulating vessel provided in the fuel system of the engine, the present invention can be embodied as an abnormality diagnosis device for any sensor.

  DESCRIPTION OF SYMBOLS 1 ... Fuel tank, 2 ... Supply pump, 3 ... Common rail, 4 ... Fuel addition valve, 5 ... Injector, 6 ... Feed valve, 7 ... Pressure reducing valve, 8 ... Fuel pressure sensor, 9 ... Check valve, 10 ... Electronic control unit (ECU: estimation means, determination means).

Claims (6)

In a fuel pressure sensor abnormality diagnosis device that performs abnormality diagnosis of a fuel pressure sensor that detects fuel pressure in a pressure accumulating vessel provided in an engine fuel system,
Estimating means for estimating the fuel pressure of the pressure accumulating vessel;
Based on a comparison between the degree of change in the detected value of the fuel pressure sensor during the transient operation of the engine and the degree of change in the estimated value of the fuel pressure by the estimating means during the transient operation, the abnormality of the fuel pressure sensor An abnormality diagnosis apparatus for a fuel pressure sensor, comprising: determination means for determining presence or absence. The abnormality diagnosis device for a fuel pressure sensor according to claim 1, wherein the determination unit performs the determination using a trajectory length of the transition curve of the fuel pressure as an index value of the degree of change. The fuel pressure sensor abnormality diagnosis device according to claim 1, wherein the determination unit performs the determination using a time area of the fuel pressure transition curve as an index value of the degree of change. The abnormality diagnosis device for a fuel pressure sensor according to claim 2 or 3, wherein the determination unit performs the determination based on an integrated value of the index values in a predetermined determination period. The determination unit, when the deviation between the index value of the change degree of the detected value and the index value of the change degree of the estimated value becomes excessive, immediately determines that there is an abnormality at the time. An abnormality diagnosis device for fuel pressure sensors. The determination means determines whether or not there is an abnormality by comparing a change degree of the detected value and the estimated value when the transient operation is continued for a predetermined determination period, and the transient operation of the engine is intermittently performed. 6. When the duration of the transient operation that has been performed is less than the determination period, abnormality diagnosis is performed using an integrated value of the index values of the degree of change during the period in which the transient operation is established. The abnormality diagnosis device for a fuel pressure sensor according to claim 1.

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