JP3721922B2 - Failure diagnosis device for fuel level sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a fuel level sensor failure diagnosis device, and more particularly to a fuel level sensor failure diagnosis device that performs failure diagnosis of a fuel level sensor that detects the level of fuel in a fuel tank.
[0002]
[Prior art]
  In a fuel tank that stores fuel supplied to an engine mounted on a vehicle, a fuel level sensor that detects the level of fuel in the fuel tank is provided in order to detect the fuel level. The fuel level sensor detects the fuel level and outputs a voltage corresponding to the fuel level to the control means. However, since a failure may occur in the fuel level sensor, it is necessary to diagnose the failure of the fuel level sensor.
[0003]
  Diagnosis of failure of the fuel level sensor includes failure diagnosis devices relating to disconnection and short-circuiting, and failure diagnosis devices that diagnose failures based on fuel injection amount integrated values together with abnormality in output characteristics (correlation between fuel level and output voltage).
[0004]
  Such a fuel level sensor failure diagnosis apparatus is disclosed in Japanese Patent Laid-Open No. 10-184479. The failure diagnosis device for the fuel level detection means disclosed in this publication includes a fuel injection means, a fuel tank that stores fuel to the fuel injection means, and a fuel that detects the remaining amount of fuel in the fuel tank. A level detection means and a control device, wherein the control device integrates a fuel consumption amount integration means for integrating the amount of fuel injected from the fuel injection means, a fuel level change amount detection means for receiving an output signal of the fuel level detection means, Comparing means for comparing the accumulated fuel consumption amount with the fuel level change amount, and a failure detecting device for detecting a failure of the fuel level detecting means based on a comparison signal of the comparing means, the fuel level detecting means has failed. Whether or not there is a failure, the subsequent diagnosis can be prohibited / cancelled.
[0005]
[Problems to be solved by the invention]
  Incidentally, in the conventional fuel level sensor failure diagnosis apparatus, the applicant of the present invention has a prior application.
[0006]
  This prior application diagnoses the abnormality of the fuel level sensor based on the fluctuation width of the fuel during traveling at a constant speed and diagnoses the abnormality of the fuel level sensor based on the fluctuation frequency of the output value of the fuel level sensor.
[0007]
  However, as shown in FIG. 10, the amount of vibration of the fuel increases when the amount of fuel is large, and conversely when the amount of fuel is small, the amount of vibration decreases.
[0008]
  As a result, when the fuel fluctuation for the fuel level sensor abnormality diagnosis determination (CFLdel) is set when the fuel is low, the fluctuation is large when the fuel is large, so the abnormality is detected even though the fuel level sensor is normal. There is a problem that the reliability of the diagnosis is lowered.
[0009]
  Conversely, if the fuel fluctuation width (CFLdel) for fuel level sensor abnormality diagnosis determination is set when there is a large amount of fuel, there is a disadvantage that it cannot be diagnosed whether or not the fuel level sensor is abnormal when the fuel is small.
[0010]
  Furthermore, there are some which try to diagnose whether or not the fuel level sensor is abnormal based on the fuel fluctuation width when the vehicle speed is 0 (zero), but even if the vehicle speed is 0 (zero), The fuel sway does not subside when entering the stop state or the fuel sway due to the fuel return phenomenon is in the situation shown in FIG. 10 depending on the amount of fuel, and the fuel level sensor malfunctions at a constant speed during traveling. There is an inconvenience that a problem similar to that at the time of diagnosis determination occurs.
[0011]
[Means for Solving the Problems]
  Accordingly, in order to eliminate the above-described disadvantage, the present invention detects a fuel level in a fuel tank that stores fuel supplied to an engine mounted on a vehicle, and outputs a voltage corresponding to the fuel level. In the fuel level sensor failure diagnosis device for diagnosing sensor failure,A fuel level average value is calculated based on the fuel level value detected by the fuel level sensor, and the abnormality diagnosis smoothing gain is set so that the fuel level average value decreases as the fuel level average value increases. The abnormality diagnosis determination fuel level is calculated using the fuel level and the abnormality diagnosis smoothing gain, and calculated for each detected fuel level value. The amount of fuel change is calculated from the difference between the maximum value and the minimum value, and the fuel fluctuation width for abnormality diagnosis determination set so as to increase as the fuel level average value of the fuel level increases, When the fuel change amount is larger than the fuel fluctuation width for abnormality diagnosis determination, the fuel level sensor is diagnosed as abnormal.It is characterized by that.
0012]
DETAILED DESCRIPTION OF THE INVENTION
  By inventing as described above, when diagnosing abnormality of the fuel level sensor,The fuel level average value is calculated based on the fuel level value detected by the fuel level sensor, and the abnormality diagnosis smoothing gain is set so that the fuel level average value decreases as the fuel level average value increases. And calculating the abnormality diagnosis determination fuel level using the fuel level and the abnormality diagnosis smoothing gain, and calculating a maximum value of the abnormality diagnosis determination fuel level calculated for each detected fuel level value. Calculate the amount of fuel change from the difference from the minimum value, calculate the fuel fluctuation width for abnormality diagnosis judgment that is set to increase as the average fuel level of the fuel level increases, and the amount of fuel change is abnormal When the fuel fluctuation width for diagnosis judgment is larger than that, it is diagnosed that the fuel level sensor is abnormal,The abnormality diagnosis of the fuel level sensor is accurately performed to improve the reliability of the diagnostic control.
0013]
【Example】
  Embodiments of the present invention will be described below in detail with reference to the drawings.
0014]
  1 to 9 show an embodiment of the present invention. 9, 2 is an engine mounted on a vehicle (not shown), 4 is a cylinder block, 6 is a cylinder head, 8 is an oil pan, 10 is a crankshaft, 12 is an air cleaner, 14 is an intake pipe, and 16 is a throttle. The body, 18 is a throttle valve, 20 is a surge tank, 22 is an intake manifold, 24 is an exhaust manifold, 26 is a front catalytic converter, 28 is an exhaust pipe, 30 is a rear catalytic converter, and 32 is a fuel tank.
0015]
  The fuel tank 32 is provided with a fuel level sensor 34 that detects the fuel level in the fuel tank 32 and outputs a voltage corresponding to the fuel level.
0016]
  An evaporated fuel control device 36 is provided between the surge tank 20 and the fuel tank 32. In the evaporated fuel control device 36, a canister 42 is provided between an evaporation passage 38 that communicates with the fuel tank 32 and a purge passage 40 that communicates with the surge tank 20. The evaporation passage 38 is provided with a tank internal pressure sensor 44, a separator 46, and a pressure control valve 48 sequentially from the fuel tank 32 side. The pressure control valve 48 communicates with the surge tank 20 via the pressure passage 50. A negative pressure valve control valve 52 is provided in the pressure passage 50. A purge valve 54 is provided in the purge passage 40. The canister 42 is provided with an atmospheric control valve 56.
0017]
  The intake system of the engine 2 is provided with an EGR device 58 that supplies a part of the exhaust gas to the intake system. The EGR device 58 includes an EGR control valve 60, a back pressure control valve 62, and an EGR determination valve 64.
0018]
  Further, the surge tank 20 is provided with a pressure sensor 68 that detects the intake pipe pressure via the filter 66.
0019]
  The engine 2 is provided with a crank angle sensor 70. The crank angle sensor 70 also has a function as an engine speed sensor, is attached to the crankshaft 10 and has a plurality of teeth 72 on the outer peripheral edge, and an electromagnetic pickup attached to the cylinder block 4. 76.
0020]
  This crank angle sensor 70 is in communication with a control means (ECU) 78.
0021]
  The control means 78 also includes a water temperature sensor 80 attached to the cylinder head 6, an intake air temperature sensor 82 attached to the intake pipe 14, a throttle opening sensor 84 attached to the throttle body 16, an ignition device 86, Fuel level sensor 34, pressure sensor 68, tank internal pressure sensor 44, negative pressure control valve 52, atmospheric control valve 56, purge valve 54, EGR control valve 60, EGR determination valve 64, and exhaust manifold 24 A front oxygen concentration sensor 88 attached to the rear catalytic converter 30, a rear oxygen concentration sensor 90 attached to the exhaust pipe 28 on the downstream side of the rear catalytic converter 30, an atmospheric pressure sensor 92 for detecting atmospheric pressure, and an acceleration for detecting the behavior state of the vehicle. (G)SEA sensor 94, a battery 96, an ignition key 98, and an alarm device 100 that informs the driver are in communication.
0022]
  The control means 78 includes an abnormality diagnosis unit 78a for diagnosing abnormality of the fuel level sensor 34 and a timer 78b.
0023]
  For reference, here, in the prior application filed by the applicant of the present invention, the control means 78 determines the fuel sway by determining the fuel sway, for example, every constant time when the engine load is constant. The fuel sway determination timer time COUNT2, which is a time during which the fuel change amount FLdel is smaller than the fuel sway determination value CFLdel when CTime> FLCOUNT elapses, is set as the fuel determination time CTIME2 set longer than the time FLCOUNT. When the shaking determination time FLCOUNT is not reached, the fuel level sensor 34 has a function of diagnosing that it is abnormal (see FIGS. 4 and 5).
0024]
  The above-described constant state of the engine load is measured by, for example, a throttle change amount THdel, an air amount change amount, a fuel injection amount change amount, an engine load change amount, and the like.
0025]
  Further, the control means 78 does not diagnose the fuel level sensor 34 when the value G of the signal from the acceleration sensor 94 that detects the behavior state of the vehicle is larger than the G sensor change determination value CGdel.
0026]
  Further, when the acceleration sensor 94 is not provided, the control unit 78 software determines that the vehicle is traveling on a rough road and the angular velocity change amount of the engine 2 is larger than the angular velocity change determination value.KiIf the determination is yes, the rough road determination flag is substituted, and the fuel level sensor 34 is not diagnosed.
0027]
  In view of the prior application as described above, the control means 78 is supplied with an abnormality diagnosis determination fuel fluctuation determination value CFLdel which is an abnormality diagnosis determination fuel fluctuation width based on a fuel level average value FLVLave that gradually increases or decreases in accordance with the increase or decrease of the fuel level FLVL. A configuration is provided that includes an abnormality diagnosing unit 78a that diagnoses an abnormality of the fuel level sensor 34 by comparing the fuel fluctuation determination value CFLdel for abnormality diagnosis determination with the fuel change amount FLdel that is the fuel fluctuation width of the fuel level FLVL. It was.
0028]
  Specifically, the raw data of the fuel level FLVL is measured, and from the raw data of the fuel level FLVL, the formula
    FLVLave = (FLVL × CFL + FLVLo) / 2
      FLVLo: Previous FLVLave
To calculate the fuel level average value FLVLave. At this time, the fuel level gain CFL is set to the fuel level sensor failure diagnosis annealing gain CFLG shown in FIG.
    CFLG ≧ CFL
Is a satisfying relationship.
0029]
  Further, as shown in FIG. 7, an abnormality diagnosis determination fuel fluctuation determination value CFLdel which is an abnormality diagnosis determination fuel fluctuation width is set from the fuel level average value FLVLave.
0030]
  Further, an abnormality diagnosis determination fuel level FLVLmf is set in the control means 78 using a smoothing gain CFLG that varies depending on the fuel level average value FLVLave, and the abnormality diagnosis determination fuel fluctuation width of the abnormality diagnosis determination fuel level FLVLmf is set. The abnormality diagnosing unit 78a for diagnosing the abnormality of the fuel level sensor 34 by the abnormality diagnosis determination fuel fluctuation determination value CFLdel.
0031]
  The abnormality diagnosis determination fuel level FLVLmf is obtained by a fuel level sensor failure diagnosis smoothing gain CFLG that varies variously depending on the fuel level average value FLVLave, as shown in FIG. That is, the abnormality diagnosis determination fuel level FLVLmf is expressed by the equation
    FLVLmf = (FLVL × CFLG + FLVLmfo) / 2
      FLVLmfo: Previous value
Ask for.
0032]
  Furthermore, the abnormality diagnosis determination fuel level FLVLmf and the fuel level average value FLVLave are set in the control means 78 by different fuel level gains CFLG and CFL, and the abnormality diagnosis fuel fluctuation width of the abnormality diagnosis determination fuel level FLVLmf is set. An abnormality diagnosis unit 78a for diagnosing an abnormality of the fuel level sensor 34 by a certain abnormality diagnosis determination fuel fluctuation determination value CFLdel is adopted.
0033]
  Further, the control means 78 calculates the fuel change amount FLdel based on the difference between the maximum value FLVLmfmax and the minimum value FLVLmfmin of the abnormality diagnosis determination fuel level FLVLmf, and the abnormality diagnosis determination fuel level FLVLmf. An abnormality diagnosis unit 78a that calculates an abnormality diagnosis determination fuel shake determination value CFLdel that is a width and diagnoses an abnormality of the fuel level sensor 34 based on the abnormality diagnosis determination fuel shake determination value CFLdel of the abnormality diagnosis determination fuel level FLVLmf. It is set as the structure provided.
0034]
  That is, the abnormality diagnosis unit 78a of the control means 78 calculates the fuel level average value FLVLave based on the value of the fuel level detected by the fuel level sensor 34, and as shown in FIG. An abnormality diagnosis smoothing gain CFLG set so as to become smaller as the average value FLVLave becomes larger is set, and the fuel for abnormality diagnosis determination is set using the fuel level and the abnormality diagnosis annealing gain CFLG. The level FLVLmf is calculated, and the fuel change amount FLdel is calculated from the difference between the maximum value FLVLmfmax and the minimum value FLVLmfmin of the abnormality diagnosis determination fuel level FLVLmf calculated for each detected fuel level value, as shown in FIG. Thus, the fuel level average value FLVLave of the fuel level increases as the value increases. An abnormality diagnosis determination fuel fluctuation determination value CFLdel which is an abnormality diagnosis determination fuel fluctuation width set so as to be a certain value is calculated, and the fuel change amount FLdel is the abnormality diagnosis determination fuel fluctuation width. When it is larger than the determination fuel fluctuation determination value CFLdel, it is diagnosed that the fuel level sensor is abnormal.
0035]
  Next, the operation of this embodiment will be described based on the flowcharts of FIGS. 1 to 3 and the time charts of FIGS.
0036]
  As shown in FIG. 2, when the engine 2 is started and the program of the control means 78 is started (step 102), it is first determined whether or not the timer establishment flag FLFLG1 is 1 (step 104).
0037]
  The timer establishment flag FLFLG1 is set to 1 based on the flowchart of FIG. That is, when the timer 78b is started (step 202), the amount of change such as the throttle change amount THdel, the air amount change amount, the fuel injection amount change amount, and the engine load change amount within a certain time (see FIG. 4) is measured (step step). 204) Then, for example, it is determined whether or not throttle change amount THdel ≦ throttle change determination value CTHdel (step 206). If step 206 is NO, the engine load is not constant, so the process returns to step 204 and the fuel level sensor 34 is not diagnosed.
0038]
  If step 206 is YES, it is determined whether the value G of the signal from the acceleration sensor 94 is G ≦ G sensor change determination value CGdel (step 208). When this step 208 is NO, G ≧ G sensor change determination value CGdel, and the running state of the vehicle is not a constant state, so the process returns to step 204 and the fuel level sensor 34 is not diagnosed.
0039]
  When step 208 is YES, a constant load condition satisfaction timer time COUNT1 such as constant throttle is counted up (step 210).
0040]
  Then, it is determined whether or not a constant load condition establishment timer time COUNT1 ≧ load determination time CTime (step 212). If step 212 is NO, the process returns to step 204.
0041]
  If step 212 is YES, the timer establishment flag FLFLG1 is set to 1 (step 214). Then, the program is ended (step 216).
0042]
  In FIG. 2, when step 104 is NO, the determination whether the timer establishment flag FLFLG1 is 1 is continued (step 104).
0043]
  If this step 104 is YES, it is determined whether or not the fuel shake determination flag FLFLG2 is 1 (step 106).
0044]
  Whether or not the fuel fluctuation determination flag FLFLG2 is 1 is determined based on the flowchart of FIG. That is, when the engine 2 is started (step 302), changes such as a throttle change amount THdel, an air amount change amount, a fuel injection amount change amount, and an engine load change amount within a predetermined time are measured (step 304), and For example, it is determined whether or not throttle change amount THdel ≦ throttle change determination value CTHdel (step 306). If step 306 is NO, the engine load is not constant, so the process returns to step 304 and the fuel level sensor 34 is not diagnosed.
0045]
  If step 306 is YES, it is determined whether or not the value G of the signal from the acceleration sensor 94 is G ≦ G sensor change determination value CGdel (step 308). When this step 308 is NO, G ≧ G sensor change determination value CGdel, and the running state of the vehicle is not constant, so the process returns to step 304 and the fuel level sensor 34 is not diagnosed.
0046]
  When step 308 is YES, raw data of the fuel level FLVL is measured (step 310).
0047]
  From the raw data of this fuel level FLVL,
    FLVLave = (FLVL × CFL + FLVLo) / 2
      FLVLo: Previous FLVLave
To calculate an average fuel level FLVLave (step 312). At this time, the fuel level gain CFL is set to the fuel level sensor failure diagnosis smoothing gain CFLG shown in FIG.
    CFLG ≧ CFL
Is set to satisfy the relationship.
0048]
  Next, a failure diagnosis determination of the fuel level sensor 34, that is, a fuel level FLVLmf for abnormality diagnosis determination is expressed by an equation
    FLVLmf = (FLVL × CFLG + FLVLmfo) / 2
      FLVLmfo: Previous value
(Step 314).
0049]
  After step 314, the maximum value FLVLmfmax and the minimum value FLVLmfmin of the abnormality diagnosis determination fuel level FLVLmf during the measurement period are measured (step 316).
0050]
  The fuel change amount FLdel is calculated based on the difference between the maximum value FLVLmfmax and the minimum value FLVLmfmin of the measured abnormality diagnosis determination fuel level FLVLmf. That is, the formula
    FLdel = FLVLmfmax−FLVLmfmin
(Step 318). Therefore, the fuel change amount FLdel uses the fuel level sensor failure diagnosis smoothing gain CFLG.
0051]
  Thereafter, an abnormality diagnosis determination fuel fluctuation determination value CFLdel, which is the abnormality diagnosis determination fuel fluctuation width, is obtained from FIG. 7 (step 320). That is, the gain CFL is used as the abnormality diagnosis determination fuel shake determination value CFLdel.
0052]
  Then, it is determined whether or not the fuel change amount FLdel <the fuel fluctuation determination value CFLdel (step 322). If this step 322 is NO, a delay tdl is performed (step 324) (see FIG. 4), and the process returns to step 304.
0053]
  If step 322 is YES, the fuel shake determination timer time COUNT2 is counted up (step 326).
0054]
  Then, it is determined whether or not the fuel shake determination timer time COUNT2 ≧ the fuel shake determination time FLCOUNT (step 328).
0055]
  When this step 328 is NO, when the fuel change amount FLdel is smaller than the fuel fluctuation determination value CFLdel, the time of this state is less than the fuel fluctuation determination time FLCOUNT, and the fuel fluctuation is within a certain range. Since it is determined that it does not fit, the process returns to step 304.
0056]
  If step 328 is YES, the fuel shake determination flag FLFLG2 is set to 1 (step 330). Then, the program is ended (step 332).
0057]
  In FIG. 2, when step 106 is YES, that is, the fuel fluctuation determination flag FLFLG2 becomes 1, and the fuel level sensor 34 is diagnosed as normal (step 108).
0058]
  However, if step 106 is NO, it is determined that the fuel fluctuation has not fallen within a certain range even though the fuel change amount FLdel is smaller than the fuel fluctuation determination value CFLdel, and the fuel level The sensor 34 diagnoses the abnormality and notifies the driver (driver) with the warning device 100 such as a lamp (step 110).
0059]
  After the processing of step 108 and step 110 described above, the program is ended (step 112).
0060]
  As a result, the fuel shake determination value CFLdel for abnormality diagnosis determination, which is the fuel fluctuation width for abnormality diagnosis, is set by the fuel level average value FLVLave that gradually increases or decreases according to the increase or decrease of the fuel level FLVL, and this fuel shake determination for abnormality diagnosis determination The control means 78 having an abnormality diagnosing unit 78a for diagnosing an abnormality of the fuel level sensor 34 by comparing the value CFLdel and the fuel change amount FLdel which is the fuel fluctuation width of the fuel level FLVL is used to increase or decrease the fuel level FLVL. The fuel shake determination value CFLdel for abnormality diagnosis determination, which is the fuel fluctuation width for abnormality diagnosis determination, can be set by the fuel level average value FLVLave that gradually increases or decreases accordingly, and the fuel level corresponding to the fuel level average value FLVLave of the fuel level FLVL Abnormal diagnosis of sensor 34 can be accurately performed, And give improved reliability of control, it is practically advantageous.
0061]
  Further, an abnormality diagnosis determination fuel level FLVLmf is set by using an annealing gain CFLG that varies depending on the fuel level average value FLVLave, and an abnormality diagnosis determination fuel level for abnormality diagnosis determination of the abnormality diagnosis determination fuel level FLVLmf. By using the control means 78 including the abnormality diagnosing unit 78a for diagnosing abnormality of the fuel level sensor 34 based on the fuel fluctuation determination value CFLdel, abnormality diagnosis is performed using the smoothing gain CFLG that varies variously depending on the fuel level average value FLVLave. The determination fuel level FLVLmf can be set, the setting accuracy of the abnormality diagnosis determination fuel level FLVLmf can be improved, the abnormality diagnosis of the fuel level sensor 34 can be accurately performed, and the reliability of diagnostic control is improved. This is practically advantageous.
0062]
  Further, the abnormality diagnosis determination fuel level FLVLmf and the fuel level average value FLVLave are set by different fuel level gains CFLG and CFL, and the abnormality diagnosis determination fuel fluctuation that is the abnormality diagnosis fuel fluctuation width of the abnormality diagnosis determination fuel level FLVLmf. By using the control means 78 including the abnormality diagnosis unit 78a for diagnosing abnormality of the fuel level sensor 34 by the determination value CFLdel, the abnormality diagnosis determination fuel level FLVLmf can be set by the fuel level gain CFLG, and the fuel The level average value FLVLave can be set by the fuel level gain CFL, and the accuracy of setting the abnormality diagnosis determination fuel level FLVLmf and the fuel level average value FLVLave can be further improved, so that the abnormality diagnosis of the fuel level sensor 34 can be accurately performed. line It can, and obtained by improving the reliability of the diagnosis control is advantageous in practical use.
0063]
  Furthermore, the fuel change amount FLdel is calculated based on the difference between the maximum value FLVLmfmax and the minimum value FLVLmfmin of the abnormality diagnosis determination fuel level FLVLmf, and the abnormality diagnosis is a fuel fluctuation width for abnormality diagnosis determination of the abnormality diagnosis determination fuel level FLVLmf. The control means 78 includes an abnormality diagnosis unit 78a that calculates a determination fuel fluctuation determination value CFLdel and diagnoses an abnormality of the fuel level sensor 34 using the abnormality diagnosis determination fuel fluctuation determination value CFLdel of the abnormality diagnosis determination fuel level FLVLmf. Thus, the fuel change amount FLdel can be calculated from the difference between the maximum value FLVLmfmax and the minimum value FLVLmfmin of the fuel level FLVLmf for abnormality diagnosis determination, and the abnormality diagnosis of the fuel level sensor 34 along the fuel level FLVL can be accurately performed. In Can Tashi.
0064]
【The invention's effect】
  As described above in detail, according to the present invention, a fuel level sensor that detects a fuel level in a fuel tank that stores fuel supplied to an engine mounted on a vehicle and outputs a voltage corresponding to the fuel level. In the fuel level sensor failure diagnosis device for diagnosing the failure ofThe fuel level average value is calculated based on the fuel level value detected by the fuel level sensor, and the abnormality diagnosis smoothing gain is set so that the fuel level average value decreases as the fuel level average value increases. The fuel level for abnormality diagnosis determination is calculated using the fuel level and the abnormality diagnosis smoothing gain, and the maximum value and minimum value of the fuel level for abnormality diagnosis determination calculated for each detected fuel level value The fuel change amount is calculated from the difference from the value, the fuel fluctuation width for abnormality diagnosis determination that is set to become larger as the fuel level average value of the fuel level becomes larger is calculated, and the fuel change amount is determined as an abnormality diagnosis. When the fuel fluctuation width for judgment is larger than that, the fuel level sensor is diagnosed as abnormalTherefore, the abnormality diagnosis of the fuel level sensor can be performed accurately, and the reliability of diagnosis control can be improved, which is practically advantageous.
[Brief description of the drawings]
FIG. 1 is a flowchart of fuel level fluctuation measurement showing an embodiment of the present invention.
FIG. 2 is a flowchart of a fuel level sensor diagnosis.
FIG. 3 is a flowchart of a timer establishment flag.
FIG. 4 is a time chart for diagnosis of a fuel level sensor.
FIG. 5 is a diagram showing a fuel level change state.
FIG. 6 is a diagram showing a relationship between a fuel level sensor failure diagnosis smoothing gain (CFLG) and a fuel level;
FIG. 7 is a diagram showing a relationship between a fuel fluctuation width for fuel level sensor failure diagnosis and a fuel level.
FIG. 8 is a diagram showing the relationship between CFL and CFLG and fuel level.
FIG. 9 is a system configuration diagram of the failure diagnosis apparatus.
FIG. 10 is a time chart showing a fuel swaying state during constant speed running and idling showing the prior art of the present invention.
[Explanation of symbols]
    2 Engine
  12 Air cleaner
  14 Intake pipe
  18 Throttle valve
  26 Front catalytic converter
  28 Exhaust pipe
  30 Rear catalytic converter
  32 Fuel tank
  34 Fuel level sensor
  36 Evaporative fuel control device
  42 Canister
  44 Tank pressure sensor
  48 Pressure control valve
  52 Negative pressure control valve
  54 Purge valve
  56 Air control valve
  58 EGR equipment
  68 Pressure sensor
  70 Crank angle sensor
  78 Control means (ECU)
  78a Abnormality diagnosis part
  80 Water temperature sensor
  82 Intake air temperature sensor
  84 Throttle opening sensor
  86 Ignition system
  88 Front oxygen concentration sensor
  90 Rear oxygen concentration sensor
  92 Atmospheric pressure sensor
  94 Acceleration (G)SESensor

Claims (1)

In a fuel level sensor failure diagnosis apparatus for detecting a fuel level in a fuel tank that stores fuel supplied to an engine mounted on a vehicle and diagnosing a failure of a fuel level sensor that outputs a voltage corresponding to the fuel level The fuel level average value is calculated based on the fuel level value detected by the fuel level sensor, and the abnormality diagnosis smoothing is set so that the fuel level average value becomes smaller as the fuel level average value becomes larger. An abnormality diagnosis determination fuel level is calculated for each detected fuel level by setting a gain, using the fuel level and the abnormality diagnosis smoothing gain to calculate a fuel level for abnormality diagnosis determination The fuel change amount is calculated from the difference between the maximum value and the minimum value of the level so that the value increases as the average fuel level of the fuel level increases. Calculating the set abnormality diagnosis determination fuel swing width, the fuel variation is, the abnormality diagnosis determination fuel swing width during larger, the fuel level, characterized in that the fuel level sensor is diagnosed to be abnormal Sensor failure diagnosis device.

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