JP5949578B2 - Abnormality diagnosis device for fuel pressure sensor - Google Patents

Description

  The present invention relates to an abnormality diagnosis device for a fuel pressure sensor for diagnosing the presence or absence of an abnormality of a fuel pressure sensor that detects a fuel pressure.

  Patent Document 1 discloses a fuel pressure sensor that detects the pressure of fuel supplied to a fuel injection valve in a fuel injection system that distributes high-pressure fuel from a common rail (accumulation vessel) to a fuel injection valve provided in each cylinder of the internal combustion engine. Has been. Note that the fuel pressure sensor described in Patent Document 1 is attached to the common rail, and the pressure (rail pressure) in the common rail is controlled so that the detected value of the fuel pressure sensor becomes a target value. And whether the abnormality has arisen in such a fuel pressure sensor is diagnosed with the following method.

  That is, when fuel is injected from the fuel injection valve, the rail pressure decreases with the injection. Therefore, when the amount of decrease in the detected value of the fuel pressure sensor caused by the fuel injection is greatly deviated from the assumed amount of decrease (reference decrease amount), it is diagnosed that an abnormality has occurred in the fuel pressure sensor.

JP 2006-77709 A

  Here, the fuel pressure sensor outputs an output signal of a level corresponding to the fuel pressure as a detection value. However, when the fuel pressure sensor has deteriorated over time, the output signal may be offset (in parallel), resulting in an abnormal state. In this case, since the inclination of the output signal is normal, the amount of decrease in the detected value of the fuel pressure sensor does not greatly deviate from the reference amount of decrease. Therefore, when such an offset abnormality occurs, the conventional diagnostic method makes a false diagnosis as normal, and the abnormality of the fuel pressure sensor cannot be detected.

  The present invention has been made in order to solve the above-described problem, and an object of the present invention is to make it possible to diagnose the fuel pressure sensor offset abnormality and to diagnose the fuel pressure sensor in which the abnormality has occurred in more detail. An object of the present invention is to provide a sensor abnormality diagnosis device.

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

1st invention is provided in each cylinder of an internal combustion engine provided with four or more cylinders (# 1- # 4), the fuel injection valve (10) which injects a fuel from an injection hole (11b), and each fuel injection A fuel pressure sensor (20) for detecting a fuel pressure in each fuel passage (11a) to the nozzle hole of the valve, and a fuel pressure sensor abnormality diagnosis device applied to a fuel injection system, a first abnormality specifying unit configured to specify a first fuel pressure sensor is first fuel pressure sensor there is an abnormality of the case where the first fuel pressure sensor specified by said first abnormality specifying unit, the first A simultaneous detection unit that simultaneously detects the fuel pressure by the fuel pressure sensor other than the first fuel pressure sensor when injection by the fuel injection valve corresponding to the fuel pressure sensor other than the fuel pressure sensor is not performed; Fuel pressure sensor In the outside fuel pressure sensor, the fuel pressure detected simultaneously by the simultaneous detection unit is compared by two fuel pressure sensors in a plurality of combinations, and a second abnormality has occurred due to the majority of the comparison results A second abnormality specifying unit that specifies a second fuel pressure sensor that is a fuel pressure sensor, and the internal combustion engine performs injection by the fuel injection valve in a predetermined order in the four or more cylinders, The first abnormality specifying unit is a fuel pressure sensor corresponding to a first fuel injection valve that is a fuel injection valve to be injected next, and a fuel injection valve that is to be injected next to the first fuel injection valve. The fuel pressure sensor corresponding to the two fuel injection valves sequentially detects the fuel pressure at the same time, each time corresponding to the fuel pressure sensor corresponding to the first fuel injection valve and the second fuel injection valve. The fuel pressure detected by the fuel pressure sensor is compared, and the first fuel pressure sensor is specified by majority of the comparison results .

  According to the above configuration, the fuel injection valve is provided in each cylinder of the internal combustion engine having four or more cylinders, and fuel is injected from the injection hole of each fuel injection valve. Then, the fuel pressure in each fuel passage to the injection hole of each fuel injection valve is detected by a fuel pressure sensor.

Here, the 1st fuel pressure sensor which is the 1st fuel pressure sensor in which abnormality has arisen among fuel pressure sensors is specified by the 1st abnormality specific part. The aspect in which the first abnormality specifying unit specifies the first fuel pressure sensor is arbitrary. When the first fuel pressure sensor is specified by the first abnormality specifying unit, the fuel injection valve corresponding to the fuel pressure sensor other than the first fuel pressure sensor specified by the first abnormality specifying unit is not injecting, The fuel pressure is detected simultaneously by a fuel pressure sensor other than one fuel pressure sensor. At this time, since the fuel injection valves corresponding to the fuel pressure sensors other than the first fuel pressure sensor do not perform injection, these fuel pressure sensors are in a state where the influence of the injection by the fuel injection valve is small, that is, fuel of the same level The pressure can be detected.

  Then, the simultaneously detected fuel pressure is compared by the two fuel pressure sensors, and the second fuel pressure sensor which is the second fuel pressure sensor in which an abnormality has occurred is specified. For this reason, when an offset abnormality has occurred in one fuel pressure sensor, it can be identified that an abnormality has occurred by comparison with the fuel pressure detected by the other fuel pressure sensor. Therefore, it is possible to diagnose an abnormality in the offset of the fuel pressure sensor.

Further, the fuel pressures detected at the same time are compared by two fuel pressure sensors in a plurality of combinations, and the second fuel pressure sensor is specified by the majority of the comparison results. Here, when the fuel pressure detected by the first fuel pressure sensor and the second sensor is similarly low, when the fuel pressure is compared between the first fuel pressure sensor and the second fuel pressure sensor, the first fuel pressure Both the sensor and the second fuel pressure sensor are diagnosed as normal. On the other hand, since the majority decision of the comparison result is performed in the fuel pressure sensor excluding the first fuel pressure sensor, the second sensor can be specified even when the abnormality occurs. Therefore, the fuel pressure sensor in which the abnormality has occurred can be diagnosed in more detail.
In addition, a fuel pressure sensor corresponding to the first fuel injection valve that is the fuel injection valve to be injected next at the present time, and a second fuel injection valve that is the fuel injection valve to be injected next to the first fuel injection valve The fuel pressure is simultaneously detected and compared by the corresponding fuel pressure sensor. For this reason, the fuel pressure can be compared with a combination of two fuel pressure sensors that are least affected by the pulsation of the fuel pressure. Therefore, abnormality diagnosis of the fuel pressure sensor can be performed accurately.

The schematic diagram which shows the outline of a fuel-injection system. The time chart which shows the change of the injection rate and fuel pressure corresponding to an injection command signal. The time chart which shows the fuel pressure waveform at the time of injection, the fuel pressure waveform at the time of non-injection, and the injection waveform. The graph which shows the output characteristic of a fuel pressure sensor. The time chart which shows the combination of detection value P # 1-P # 4 used for 1st abnormality identification. The schematic diagram which shows an example of an abnormality specific result. The flowchart which shows the 1st abnormality specific process sequence. The flowchart which shows the 2nd abnormality specific process sequence.

  Hereinafter, an embodiment applied to a common rail fuel injection system of an in-vehicle diesel engine will be described with reference to the drawings. The diesel engine (internal combustion engine) includes four cylinders # 1 to # 4, and injects high-pressure fuel into the cylinders to perform compression self-ignition combustion.

  FIG. 1 is a schematic diagram showing an outline of a fuel injection system. First, an engine fuel injection system including the fuel injection valve 10 will be described.

  The fuel in the fuel tank 40 is pumped to the common rail 42 (pressure accumulator) by the fuel pump 41 and accumulated, and distributed and supplied to the fuel injection valves 10 (# 1 to # 4) of each cylinder. The plurality of fuel injection valves 10 (# 1 to # 4) inject fuel in a predetermined order. In this embodiment, it is assumed that repeated injection is performed in the order of # 1 → # 3 → # 4 → # 2.

  A plunger pump is used as the fuel pump 41, and fuel is pumped in synchronism with the reciprocating movement of the plunger. The fuel pump 41 is driven by the crankshaft using the engine output as a drive source, and pumps the fuel by a predetermined number of times during a period of injection in the order of # 1 → # 3 → # 4 → # 2.

  The fuel injection valve 10 includes a body 11, a needle-shaped valve body 12, an electric actuator 13, and the like described below. The body 11 has a high-pressure passage 11a formed therein and a nozzle hole 11b for injecting fuel. The valve body 12 is accommodated in the body 11 and opens and closes the nozzle hole 11b.

  A back pressure chamber 11c for applying a back pressure to the valve body 12 is formed in the body 11, and the high pressure passage 11a and the low pressure passage 11d are connected to the back pressure chamber 11c. The electric actuator 13 operates the control valve 14 so as to switch the communication state between the high pressure passage 11a and the low pressure passage 11d and the back pressure chamber 11c. The driving of the electric actuator 13 is controlled by the ECU 30.

  When the control valve 14 is operated so that the back pressure chamber 11c communicates with the low pressure passage 11d, the fuel pressure in the back pressure chamber 11c decreases, the valve body 12 is lifted (valve opening operation), and the nozzle hole 11b is opened. It is. As a result, the high-pressure fuel supplied from the common rail 42 to the high-pressure passage 11a is injected from the injection hole 11b into the combustion chamber. On the other hand, when the control valve 14 is operated so that the back pressure chamber 11c communicates with the high pressure passage 11a, the fuel pressure in the back pressure chamber 11c rises and the valve body 12 is lifted down (closed operation), and the nozzle hole 11b. Is closed and fuel injection is stopped.

  The fuel pressure sensor 20 includes a stem 21 (a strain generating body), a pressure sensor element 22 and the like described below. The stem 21 is attached to the body 11, and the diaphragm portion 21a formed in the stem 21 is elastically deformed by receiving the pressure of the high-pressure fuel flowing through the high-pressure passage 11a (fuel passage). The pressure sensor element 22 is attached to the diaphragm portion 21a, and outputs a pressure detection signal to the ECU 30 in accordance with the amount of elastic deformation generated in the diaphragm portion 21a.

  The fuel pressure sensor 20 is mounted on all the fuel injection valves 10. In the following description, the fuel injection valve 10 mounted in the cylinder # 1 is described as the injection valve 10 (# 1), and the fuel pressure sensor 20 mounted in the injection valve 10 (# 1) is described as the sensor 20 (# 1). To do. Similarly, the fuel injection valve 10 and the fuel pressure sensor 20 mounted on the cylinders # 2 to # 4 are referred to as an injection valve 10 (# 2 to # 4) and a sensor 20 (# 2 to # 4).

  The ECU 30 (electronic control device) is a known microcomputer including a CPU, ROM, RAM, storage device, input / output interface, and the like. The ECU 30 calculates a target injection state (the number of injection stages, the injection start timing, the injection end timing, the injection amount, etc.) based on the operation amount of the accelerator pedal of the vehicle, the engine load, the engine speed NE, and the like. For example, the optimal injection state corresponding to the engine load and the engine speed is stored as an injection state map. Based on the current engine load and engine speed, the target injection state is calculated with reference to the injection state map.

  Injection command signals t1, t2, and tq (see FIG. 2A) corresponding to the calculated target injection state are set based on injection rate parameters td, te, and Rmax described in detail later. The learned values of these injection rate parameters are detected by the change in the detected value (pressure waveform) of the fuel pressure sensor 20.

  Next, a method for detecting and learning the injection rate parameter will be described below with reference to FIGS. In the following description, learning is based on the detection value of the sensor 20 (# 1) when fuel is injected by the injection valve 10 (# 1). This is the same, and the injection rate parameter is learned based on the detection value of the fuel pressure sensor 20 mounted on the fuel injection valve 10 that is injecting.

  For example, when fuel is injected by the injection valve 10 (# 1), a change in fuel pressure caused by the injection is detected as a fuel pressure waveform (see FIG. 2C) based on the detection value of the sensor 20 (# 1). An injection state is detected by calculating an injection rate waveform (see FIG. 2B) representing a change in fuel injection amount per unit time based on the detected fuel pressure waveform. The injection rate parameters td, te, and Rmax that specify the detected injection rate waveform (injection state) are learned and used for injection control of the injection valve 10 (# 1).

  The detected value of the sensor 20 (# 1) shown in the fuel pressure waveform of FIG. 2 (c) starts to descend from the inflection point P1 as the injection starts and reaches the inflection point P2 as the maximum injection rate is reached. Descent ends. Thereafter, the lift starts at the inflection point P3 when the lift-down of the valve body 12 is started, and the lift ends at the inflection point P4 when the valve body 12 is closed and the injection is finished. Then, it attenuates while pulsating so as to repeat ascending and descending (refer to the inside of the one-dot chain line Wc).

  This fuel pressure waveform has a correlation with the injection rate waveform shown in FIG. Specifically, the appearance time of the inflection point P1 and the injection start time R1 are correlated, the appearance time of the inflection point P3 and the injection end time R4 are correlated, and the pressure from the inflection point P1 to P2 There is a correlation between the drop amount ΔP and the maximum injection rate (injection rate parameter Rmax).

  FIG. 2A shows the injection command signal output to the injection valve 10 (# 1), and the above-described injection rate parameter td is a delay time (injection start delay) of the injection start timing R1 with respect to the injection start command timing t1. Time td). The injection rate parameter te is a delay time (injection end delay time te) of the injection end timing R4 with respect to the injection end command timing t2.

  Therefore, the correlation coefficients representing the various correlations described above are obtained by testing in advance, and using these correlation coefficients, the inflection points P1 and P3 detected from the fuel pressure waveform of the sensor 20 (# 1) are obtained. The injection rate parameters td, te, and Rmax are calculated based on the appearance time and the pressure drop amount ΔP. Further, the injection rate waveform can be estimated based on these injection rate parameters td, te, and Rmax, and the injection amount is determined based on the area of the estimated injection rate waveform (see halftone dot hatching in FIG. 2B). It can also be calculated.

  As described above, by using the detection value of the fuel pressure sensor 20, it is possible to calculate and learn the actual injection state (injection rate parameters td, te, Rmax, injection amount, etc.) with respect to the injection command signal. Then, ECU 30 sets an injection command signal corresponding to the target injection state based on the learned value.

  In the following description, a cylinder that is injecting fuel from the fuel injection valve 10 is an injection cylinder (front cylinder), and a cylinder that is not injecting fuel when the injection cylinder is injecting fuel is a non-injection cylinder (back cylinder). The fuel pressure sensor 20 corresponding to the injection cylinder is referred to as an injection sensor, and the fuel pressure sensor 20 corresponding to the non-injection cylinder is referred to as a non-injection sensor.

  An injection fuel pressure waveform Wa (see FIG. 3A), which is a fuel pressure waveform detected by the injection sensor, does not represent only the influence of the injection, but a waveform generated by an influence other than the injection exemplified below. Contains ingredients. That is, when the fuel pump 41 pumps fuel intermittently like a plunger pump, when pump pumping is performed during fuel injection, the fuel pressure waveform Wa during injection during the pump pumping period is entirely Waveform with increased pressure. That is, an injection fuel pressure waveform Wa (see FIG. 3A) represents an injection waveform Wb (see FIG. 3C), which is a fuel pressure waveform representing a change in fuel pressure due to injection, and an increase in fuel pressure due to pumping. And a fuel pressure waveform (see solid line Wu in FIG. 3B).

  Even if such pump pumping is not performed during fuel injection, immediately after the fuel is injected, the fuel pressure in the entire injection system is reduced by that amount. Therefore, the fuel pressure waveform Wa at the time of injection becomes a waveform in which the pressure is lowered as a whole. That is, the injection fuel pressure waveform Wa includes a component of the injection waveform Wb that represents a change in fuel pressure due to injection and a fuel pressure waveform that represents a decrease in the fuel pressure in the entire injection system (see the dotted line Wu ′ in FIG. 3B). Contains ingredients.

  Therefore, in the present embodiment, attention is paid to the fact that the non-injection fuel pressure waveform Wu (Wu ′) detected by the non-injection sensor represents a change in the fuel pressure in the common rail 42. The injection waveform Wb is calculated by subtracting the non-injection fuel pressure waveform Wu (Wu ′) detected by the non-injection sensor from the injection fuel pressure waveform Wa detected by the injection sensor. The fuel pressure waveform shown in FIG. 2C is the injection waveform Wb.

  Further, when performing multi-stage injection, the pulsation of the fuel pressure waveform related to the previous stage injection (see within the one-dot chain line Wc in FIG. 2C) is superimposed on the fuel pressure waveform Wa. In particular, when the interval with the upstream injection is short, the fuel pressure waveform Wa is greatly affected by the pulsation due to the upstream injection. Therefore, in addition to the non-injection fuel pressure waveform Wu (Wu ′), it is desirable to calculate the injection waveform Wb by performing a process of subtracting the pulsation caused by the preceding injection from the fuel pressure waveform Wa.

  FIG. 4 is a graph showing the output characteristics of the fuel pressure sensor 20. The output voltage (detected value) of the fuel pressure sensor 20 increases in proportion to the actual fuel pressure. A solid line L1 in the figure indicates characteristics when the fuel pressure sensor 20 is normal. When the disconnection or short circuit abnormality occurs in the fuel pressure sensor 20, the output voltage becomes a value less than the threshold value TH1 or more than the threshold value TH2 regardless of the fuel pressure. Therefore, when the fuel pump 41 is operated, the ECU 30 diagnoses whether there is a disconnection or short circuit abnormality based on whether the output voltage is within the range of the threshold values TH1 to TH2.

  Further, when the aging deterioration of the fuel pressure sensor 20 progresses, the characteristic abnormality such that the inclination of the output voltage characteristic becomes different from the normal one (see the dotted line L2), or the output voltage deviates by a certain amount in parallel from the normal time. A characteristic abnormality (offset abnormality) such as (see alternate long and short dash line L3) occurs. Regarding the presence / absence of such characteristic abnormality, two fuel pressure sensors whose detected value pulsations are within a predetermined range are selected from the plurality of fuel pressure sensors 20, and the detected values of the two selected fuel pressure sensors are compared. To diagnose (identify first abnormality).

  5 indicates a combination of two selected fuel pressure sensors (pairs A to D). For example, the pair A includes the detection value P # 1 of the sensor 20 (# 1) and the sensor 20 (# A combination with the detection value P # 3 of 3) is shown. Similarly, pair B represents a combination of detection values P # 3 and P # 4, pair C represents a combination of detection values P # 4 and P # 2, and pair D represents a combination of detection values P # 2 and P # 1. .

  These combinations include the fuel pressure sensor 20 provided in the fuel injection valve 10 (first fuel injection valve) scheduled to be injected next and the fuel scheduled to be injected next to the first fuel injection valve. The fuel pressure sensor 20 is provided in the injection valve 10 (second fuel injection valve), and these fuel pressure sensors are selected as the determination target of the presence or absence of abnormality.

  Here, when injection by the fuel injection valve 10 is performed in a predetermined order in the four cylinders, the first fuel injection valve to be injected next at the present time is the longest time from the previous injection at its own fuel injection valve. This is the fuel injection valve that has passed. For this reason, the fuel pressure sensor 20 corresponding to the first fuel injection valve has the smallest influence of the pulsation of the fuel pressure. The fuel pressure sensor 20 corresponding to the second fuel injection valve in which injection is performed next to the first fuel injection valve has the influence of the pulsation of the fuel pressure smaller than that of the fuel pressure sensor 20 corresponding to the first fuel injection valve. ing.

  In addition, the detection timing of the detection values P # 1 to P # 4 sequentially detected by the fuel pressure sensor 20 corresponding to the first fuel injection valve at that time is the fuel pressure waveform of the fuel pressure sensor 20 corresponding to the first fuel injection valve. It is desirable immediately before the inflection point P1 appears. For example, the detection values P # 1 to P # 4 at the timing of the injection start command timing t1 or at a timing before the predetermined time of the timing t1 are used to determine whether there is an abnormality. Further, the detection timing of the detection values P # 1 to P # 4 by the fuel pressure sensor 20 corresponding to the second fuel injection valve at that time is the same as the detection timing of the fuel pressure sensor 20 corresponding to the first fuel injection valve. It is desirable.

  If any abnormality occurs in one of the two fuel pressure sensors 20 selected in this way, the detection values of the fuel pressure sensor 20 are greatly deviated from each other. it can. Therefore, the pressure difference between the detection value of the fuel pressure sensor 20 corresponding to the first fuel injection valve and the detection value of the fuel pressure sensor 20 sensor corresponding to the second fuel injection valve is equal to or greater than a preset threshold value Pth. The presence or absence of characteristic abnormality is diagnosed according to whether or not there is any. Then, the fuel pressure sensor that is determined to be abnormal most frequently in the comparison of the detected values in each pair A to D is specified as abnormal. That is, the first fuel pressure sensor, which is the first fuel pressure sensor 20 in which an abnormality has occurred, among the four fuel pressure sensors 20 is specified by the majority of the comparison results.

  FIGS. 6A and 6B are specific examples for explaining the method of specifying (first abnormality specifying), and show detection values P # 1 to P # 4 of each pair A to D. FIG. In addition, when the pressure difference mentioned above is more than the threshold value Pth, both the fuel pressure sensors of a corresponding pair are tentatively determined as abnormal (refer to x mark). Further, the number of temporarily determined abnormality is counted for each of the fuel pressure sensors 20 (# 1) to 20 (# 4).

  FIG. 6A is a specific example when all the fuel pressure sensors 20 (# 1) to 20 (# 4) are normal. In this case, since it is determined that the pressure difference is less than the threshold value Pth in all the pairs A to D, it is diagnosed that all the fuel pressure sensors 20 (# 1) to (# 4) are normal.

  FIG. 6B is a specific example when an abnormality occurs in which the detection value of the fuel pressure sensor 20 (# 1) is low. In this case, it is determined that the pressure difference between the pair A and the pair D is equal to or greater than the threshold value Pth. The fuel pressure sensors 20 (# 1) and 20 (# 3) applied to the pair A are temporarily determined to be abnormal, and the fuel pressure sensors 20 (# 2) and 20 (# 1) applied to the pair D are temporarily determined to be abnormal. Is done. As a result, since the fuel pressure sensor 20 (# 1) has the largest number of times that the fuel pressure sensor 20 (# 1) is temporarily determined to be abnormal, it is specified that the fuel pressure sensor 20 (# 1) is abnormal.

  FIG. 7 is a flowchart showing the first abnormality identification processing procedure described above. This series of processing is repeatedly executed at a predetermined cycle by the ECU 30 (first abnormality specifying unit).

  First, in S11 shown in the figure, the detection values P # 1 to P # 4 are compared for all the pairs A to D described above, and abnormality determination using the threshold value Pth is performed. In subsequent S12, it is determined (majority decision) which fuel pressure sensor has the highest number of times of abnormality determination.

  When there is no fuel pressure sensor determined to be abnormal (S13: NO), in S14, it is diagnosed that all the fuel pressure sensors 20 (# 1) to (# 4) are normal. On the other hand, when there is a fuel pressure sensor determined to be abnormal (S13: YES), in S15, the corresponding fuel pressure sensor 20 (the fuel pressure sensor with the highest abnormality determination) is replaced with the first fuel pressure sensor ( The first fuel pressure sensor is specified. Thereafter, this series of processing is temporarily terminated.

  Here, in the four fuel pressure sensors 20, a case where an abnormality occurs in the second fuel pressure sensor following the first fuel pressure sensor in which the abnormality has occurred will be considered. In this case, the result when the first abnormality identification is performed is shown below.

  FIG. 6C is a specific example when an abnormality occurs in which the detection values of the fuel pressure sensors 20 (# 1) and 20 (# 2) are both high. In this case, it is determined that the pressure difference between the pair A and the pair C is equal to or greater than the threshold value Pth. As a result, the number of times that the abnormality is temporarily determined is the same (once) for all the fuel pressure sensors 20 (# 1) to 20 (# 4), and therefore it is possible to specify which fuel pressure sensor 20 is abnormal. Therefore, it can only be diagnosed that one of the fuel pressure sensors 20 is abnormal.

  Therefore, in the present embodiment, when the first fuel pressure sensor in which an abnormality has occurred is specified, the second abnormality specification for specifying the second fuel pressure sensor (second fuel pressure sensor) in which the abnormality has occurred is performed. Do.

  FIG. 8 is a flowchart showing a processing procedure for identifying the second abnormality. This series of processing is repeatedly executed by the ECU 30 at a predetermined cycle.

  First, when the first fuel pressure sensor (first fuel pressure sensor) in which an abnormality has occurred has not been identified by the first abnormality identification (S21: NO), this series of processes is temporarily terminated. On the other hand, when the first fuel pressure sensor in which the abnormality has occurred is specified by the first abnormality specification (S21: YES), in S22, from the predetermined cylinder scheduled to be injected next at the present time. Also, it is determined whether or not injection by the fuel injection valve 10 is not performed in the cylinder in which the injection is performed one order before.

  When a negative determination is made in the above determination (S22: NO), this series of processes is temporarily terminated. On the other hand, when an affirmative determination is made in the above determination (S22: YES), in S23, as described above, fuel is detected by all the fuel pressure sensors 20 at the timing immediately before the inflection point P1 appears in the fuel pressure waveform of the fuel pressure sensor 20. The pressure is detected at the same time. That is, at least when the fuel injection valve 10 corresponding to the fuel pressure sensor 20 other than the first fuel pressure sensor is not injecting, the fuel pressure sensor 20 other than the first fuel pressure sensor simultaneously detects the fuel pressure.

  In subsequent S24, in the fuel pressure sensors 20 other than the first fuel pressure sensor, the detection values P # 1 to P # 4 are compared with all combinations of the two fuel pressure sensors 20, and the abnormality determination using the threshold value Pth is performed. In subsequent S25, it is determined (majority decision) which fuel pressure sensor has the largest number of times of abnormality determination. That is, in the fuel pressure sensors 20 other than the first fuel pressure sensor, the detected values P # 1 to P # 4 are compared by the two fuel pressure sensors 20 in a plurality of combinations, and the majority of the comparison results is determined.

  If there is no fuel pressure sensor determined to be abnormal (S26: NO), it is diagnosed in S27 that all fuel pressure sensors 20 (# 1) to (# 4) are normal. On the other hand, when there is a fuel pressure sensor determined to be abnormal (S26: YES), in S28, the corresponding fuel pressure sensor 20 (the fuel pressure sensor with the highest abnormality determination) is replaced with the second fuel pressure sensor ( 2nd fuel pressure sensor). Thereafter, this series of processing is temporarily terminated.

  In addition, the process of S21-S24 is equivalent to the process as a simultaneous detection part, and the process of S25-S28 is equivalent to the process as a 2nd abnormality specific part.

  For example, while the fuel is being cut off by the engine when the vehicle is decelerating, the state in which the fuel injection valve 10 does not inject fuel in the cylinder immediately before the predetermined cylinder continues to be injected. Become. For this reason, the predetermined cylinder is changed according to the predetermined order described above, and the fuel pressure is detected simultaneously by the fuel pressure sensor 20 other than the first fuel pressure sensor (S23). Then, the fuel pressures detected at the same time are compared by the two fuel pressure sensors 20 in a plurality of combinations (S24), and the second fuel pressure sensor is specified by the majority of the comparison results (S25 to S28).

  FIG. 6D is a specific example when an abnormality in which the detected value of the fuel pressure sensor 20 (# 1) is high and an abnormality in which the fuel pressure sensor 20 (# 2) is high occurs. Here, P # 1 is excluded from the comparison target as a detection value by the first fuel pressure sensor. In this case, it is determined that the pressure difference between the pair E and the pair G is equal to or greater than the threshold value Pth. The fuel pressure sensors 20 (# 2) and 20 (# 3) applied to the pair E are provisionally determined to be abnormal, and the fuel pressure sensors 20 (# 4) and 20 (# 2) applied to the pair G are provisionally determined to be abnormal. Is done. As a result, since the fuel pressure sensor 20 (# 2) has the largest number of times that the fuel pressure sensor 20 (# 2) is temporarily determined to be abnormal, it is specified that the fuel pressure sensor 20 (# 2) is abnormal.

  The embodiment described in detail above has the following advantages.

  In the first abnormality identification, the first fuel pressure sensor that is the first fuel pressure sensor 20 in which an abnormality has occurred among the fuel pressure sensors 20 (# 1 to # 4) is identified. When the fuel injection valve 10 corresponding to the fuel pressure sensor 20 other than the first fuel pressure sensor is not performing injection, the fuel pressure sensor 20 other than the first fuel pressure sensor simultaneously detects the fuel pressure. At this time, since the fuel injection valve 10 corresponding to the fuel pressure sensor 20 other than the first fuel pressure sensor does not perform injection, these fuel pressure sensors 20 are in a state where the influence of the injection by the fuel injection valve 10 is small, that is, the same level. A high fuel pressure can be detected.

  Then, the simultaneously detected fuel pressures are compared by the two fuel pressure sensors 20, and the second fuel pressure sensor, which is the second fuel pressure sensor 20 in which an abnormality has occurred, is specified. For this reason, when an offset abnormality has occurred in one fuel pressure sensor 20, it can be identified that an abnormality has occurred by comparison with the fuel pressure detected by the other fuel pressure sensor 20. Therefore, it is possible to diagnose an abnormality in the offset of the fuel pressure sensor 20.

  The comparison of the simultaneously detected fuel pressure by the two fuel pressure sensors 20 is performed in a plurality of combinations, and the second fuel pressure sensor is specified by the majority of the comparison results. Here, when the fuel pressure detected by the first fuel pressure sensor and the second sensor is similarly high, when the fuel pressure is compared between the first fuel pressure sensor and the second fuel pressure sensor, the first fuel pressure sensor And the second fuel pressure sensor are both diagnosed as normal (see pair D in FIG. 6C). On the other hand, since the majority of the comparison result is performed in the fuel pressure sensor 20 excluding the first fuel pressure sensor, the second sensor can be specified even when the abnormality occurs (FIG. 6D). reference). Therefore, it is possible to diagnose the fuel pressure sensor 20 in which an abnormality has occurred in more detail.

  When the injection by the fuel injection valve 10 is not performed in the cylinder immediately before the predetermined cylinder before the injection by the fuel injection valve 10 is performed in the predetermined cylinder, Before the fuel injection valve 10 performs the injection in the predetermined cylinder, the fuel pressure is simultaneously detected by the fuel pressure sensor 20 other than the first fuel pressure sensor. For this reason, the influence of the pulsation of the fuel pressure can be reduced as compared with the case where the injection is performed by the fuel injection valve 10 in the cylinder immediately before the predetermined cylinder. Therefore, the abnormality diagnosis of the second fuel pressure sensor can be performed more accurately.

  If the state in which the injection is performed by the fuel injection valve 10 in the cylinder immediately before the predetermined cylinder continues before the injection by the fuel injection valve 10 is performed in the predetermined cylinder, The fuel pressure is detected continuously by the fuel pressure sensors 20 other than the one fuel pressure sensor. Then, the fuel pressures detected at the same time each time are compared by the two fuel pressure sensors 20 in a plurality of combinations, and the second fuel pressure sensor is specified by the majority of the comparison results. Therefore, the opportunity to specify the second fuel pressure sensor can be increased. Furthermore, since the influence of the pulsation of the fuel pressure becomes smaller as time elapses after the injection by the fuel injection valve 10, the accuracy of abnormality diagnosis of the second fuel pressure sensor can be improved.

  -For all fuel pressure sensors 20 other than the first fuel pressure sensor, simultaneous detection of fuel pressure and comparison of fuel pressures by all combinations of the two fuel pressure sensors 20 are performed. Therefore, the number of combinations of the two fuel pressure sensors 20 can be increased, and abnormality diagnosis of the second fuel pressure sensor can be performed more accurately.

  Since the fuel pressure is simultaneously detected by the fuel pressure sensor 20 other than the first fuel pressure sensor during the fuel cut in which the fuel injection valve 10 does not perform injection in the engine, the influence of the pulsation of the fuel pressure can be extremely reduced. it can. Therefore, the accuracy of the abnormality diagnosis of the second fuel pressure sensor can be further improved.

  A fuel pressure sensor 20 corresponding to the first fuel injection valve that is the fuel injection valve 10 to be injected next at the present time, and a second fuel injection valve that is the fuel injection valve to be injected next to the first fuel injection valve The fuel pressure is detected simultaneously by the fuel pressure sensor 20 corresponding to. For this reason, the fuel pressure can be compared with a combination of the two fuel pressure sensors 20 that are least affected by the pulsation of the fuel pressure. Therefore, abnormality diagnosis of the fuel pressure sensor 20 can be performed accurately.

  Note that the above-described embodiment may be modified as follows.

  In the above embodiment, as the determination target in the first abnormality identification, the fuel pressure sensor 20 provided in the fuel injection valve 10 (first fuel injection valve) scheduled to be injected next at the present time, and the first fuel injection valve The fuel pressure sensor 20 provided in the fuel injection valve 10 (second fuel injection valve) scheduled to be injected next is employed. However, a fuel pressure sensor 20 other than the fuel pressure sensor 20 provided in the first fuel injection valve and the fuel pressure sensor 20 provided in the second fuel injection valve may be employed as a determination target in the first abnormality identification. For example, the fuel pressure sensor 20 provided in the first fuel injection valve and the fuel pressure sensor 20 provided in the fuel injection valve 10 (third fuel injection valve) scheduled to be injected next to the second fuel injection valve. It can also be adopted as a judgment object for the presence or absence of abnormality.

  When the second fuel pressure sensor in which an abnormality has occurred is identified for a fuel injection system in which the engine has five or more cylinders and the fuel injection valve 10 and the fuel pressure sensor 20 are provided in each cylinder. In addition, a third abnormality specifying unit that specifies a third fuel pressure sensor (third fuel pressure sensor) in which an abnormality has occurred may be provided. The processing by the third abnormality identification unit can be performed in accordance with the second abnormality identification of FIG. According to such a configuration, when the second fuel pressure sensor is specified, it is possible to specify the third fuel pressure sensor in which the abnormality further occurs in the remaining cylinders. Therefore, it is possible to diagnose the fuel pressure sensor 20 in which an abnormality has occurred in more detail.

  In addition, in the fuel injection system including five or more fuel injection valves 10 and fuel pressure sensors 20 as described above, the fuel pressure is targeted for a part of the fuel pressure sensors 20 other than the first fuel pressure sensor in the second abnormality identification. May be detected, and the fuel pressure may be compared by a plurality of combinations of the two fuel pressure sensors 20. For example, in a fuel injection system including six fuel injection valves 10 and six fuel pressure sensors 20, when the first fuel pressure sensor is specified, three fuel pressure sensors 20 other than the first fuel pressure sensor are selected and the three fuel pressures are selected. The second abnormality identification described above can be performed with the sensor 20 as a determination target.

  In the above embodiment, all the fuel pressures are obtained when the fuel injection valve 10 does not perform injection in the cylinder in which the injection is performed one order before the predetermined cylinder scheduled to be injected next. The fuel pressure is simultaneously detected by the sensor 20. However, when a small amount of fuel is being injected by the fuel injection valve 10 in the cylinder in which the injection is performed one order before the predetermined cylinder, the fuel pressure is simultaneously detected by all the fuel pressure sensors 20. You can also. Also in this case, the influence of fuel pressure pulsation due to the previous injection can be reduced.

  -In 1st abnormality specification, the aspect which specifies a 1st fuel pressure sensor is arbitrary. For example, similar to the second abnormality identification, the fuel pressure may be simultaneously detected by all the fuel pressure sensors 20, and the majority of the comparison results may be determined by a plurality of combinations of the two fuel pressure sensors 20. Further, the fuel pressure sensor 20 in which the disconnection or short circuit abnormality has occurred may be specified by the output voltage of the fuel pressure sensor 20 being less than the threshold value TH1 or exceeding the threshold value TH2.

  In the above embodiment, the presence / absence of characteristic abnormality is diagnosed depending on whether the pressure difference between the detection values of the two fuel pressure sensors 20 is equal to or greater than a preset threshold value Pth. However, the presence / absence of a characteristic abnormality can also be diagnosed depending on whether the ratio between the detection values of the two fuel pressure sensors 20 is equal to or greater than a preset threshold value.

  -Not only a diesel engine but the abnormality diagnosis apparatus mentioned above can also be applied to a gasoline direct injection engine provided with a delivery pipe.

  DESCRIPTION OF SYMBOLS 10 ... Fuel injection valve, 11a ... High pressure passage, 11b ... Injection hole, 20 ... Fuel pressure sensor, 30 ... ECU.

Claims (6)

A fuel injection valve (10) that is provided in each cylinder of the internal combustion engine having four or more cylinders (# 1 to # 4) and injects fuel from the injection hole (11b), and the injection holes of each fuel injection valve A fuel pressure sensor (20) for detecting a fuel pressure in each fuel passage (11a), and a fuel pressure sensor abnormality diagnosis device applied to a fuel injection system,
A first abnormality specifying unit that specifies a first fuel pressure sensor that is a first fuel pressure sensor in which an abnormality has occurred among the fuel pressure sensors;
When the first fuel pressure sensor is specified by the first abnormality specifying unit, when the fuel injection valve corresponding to the fuel pressure sensor other than the first fuel pressure sensor is not injecting, the first fuel pressure sensor A simultaneous detection unit for simultaneously detecting the fuel pressure by the fuel pressure sensor other than
In the fuel pressure sensors other than the first fuel pressure sensor, the fuel pressure detected simultaneously by the simultaneous detection unit is compared by two fuel pressure sensors in a plurality of combinations, and an abnormality occurs due to the majority of the comparison results. A second abnormality specifying unit that specifies a second fuel pressure sensor that is the second fuel pressure sensor;
Equipped with a,
In the internal combustion engine, injection by the fuel injection valve is performed in a predetermined order in the four or more cylinders,
The first abnormality specifying unit is a fuel pressure sensor corresponding to a first fuel injection valve that is a fuel injection valve to be injected next, and a fuel injection valve that is to be injected next to the first fuel injection valve. The fuel pressure sensor corresponding to the two fuel injection valves sequentially detects the fuel pressure simultaneously, and each time the fuel pressure sensor corresponding to the first fuel injection valve and the fuel pressure sensor corresponding to the second fuel injection valve are used. An abnormality diagnosis device for a fuel pressure sensor, wherein the detected fuel pressure is compared, and the first fuel pressure sensor is specified by a majority decision of a comparison result . In the internal combustion engine, injection by the fuel injection valve is performed in a predetermined order in the four or more cylinders,
The simultaneous detection unit is configured such that the order in which the fuel injection valve is injected before the injection by the fuel injection valve in the predetermined cylinder among the four or more cylinders is the cylinder immediately before the predetermined cylinder. The fuel pressure is detected simultaneously by the fuel pressure sensor other than the first fuel pressure sensor before injection by the fuel injection valve in the predetermined cylinder when injection by the fuel injection valve is not performed. An abnormality diagnosis device for a fuel pressure sensor as described in 1.   The fuel pressure according to claim 2, wherein the simultaneous detection unit continuously changes the predetermined cylinder according to the predetermined order and continuously detects the fuel pressure by the fuel pressure sensor other than the first fuel pressure sensor. Sensor abnormality diagnosis device. The simultaneous detection unit is other than the first fuel pressure sensor when injection by the fuel injection valve corresponding to all the fuel pressure sensors other than the first fuel pressure sensor specified by the first abnormality specifying unit is not performed. The fuel pressure is simultaneously detected by all the fuel pressure sensors of
The second abnormality specifying unit compares the fuel pressures detected simultaneously by the simultaneous detection unit with the two fuel pressure sensors in all combinations other than the first fuel pressure sensor. The abnormality diagnosis device for a fuel pressure sensor according to any one of claims 1 to 3, wherein the second fuel pressure sensor is specified by a majority decision of a comparison result. The internal combustion engine includes five or more cylinders,
The simultaneous detection unit may include the first fuel pressure sensor and the first fuel pressure sensor when the first fuel pressure sensor is specified by the first abnormality specifying unit and the second fuel pressure sensor is specified by the second abnormality specifying unit . When the fuel injection valve corresponding to the fuel pressure sensor other than 2 fuel pressure sensors is not injecting, the fuel pressure sensor other than the first fuel pressure sensor and the second fuel pressure sensor detects the fuel pressure simultaneously,
In the fuel pressure sensors other than the first fuel pressure sensor and the second fuel pressure sensor, the fuel pressures detected simultaneously by the simultaneous detection unit are compared by two fuel pressure sensors in a plurality of combinations. The abnormality diagnosis device for a fuel pressure sensor according to any one of claims 1 to 4, further comprising a third abnormality identification unit that identifies a third fuel pressure sensor that is a third fuel pressure sensor in which an abnormality has occurred due to a majority decision.   The said simultaneous detection part makes the said fuel pressure detected simultaneously by the said fuel pressure sensors other than a said 1st fuel pressure sensor during the fuel cut which is not injected by the said fuel injection valve in the said internal combustion engine. The abnormality diagnosis device for a fuel pressure sensor according to any one of the preceding claims.

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