JP4440132B2 - Failure diagnosis device for fuel level sensor - Google Patents

Description

  The present invention relates to a fuel level sensor failure diagnosis device that detects a remaining amount of fuel in a fuel tank that supplies fuel to a vehicle internal combustion engine.

  A fuel level sensor failure diagnosis apparatus is disclosed in Patent Document 1, for example. In this failure diagnosis device, an integrated value of the fuel injection amount in the internal combustion engine is calculated, and the change amount of the fuel level sensor output when the fuel injection amount integrated value reaches a predetermined integrated value, and the fuel injection integrated value When the difference is outside the predetermined normal range, it is determined that the fuel level sensor has failed.

Japanese Patent Laid-Open No. 10-184479

  In general, the rate at which the fuel in the fuel tank decreases is low, and the rate of decrease in the level of the fuel level detected by the fuel level sensor is very low. Therefore, in order to accurately perform the failure determination, the predetermined integrated value is set to a relatively large value, and when the fuel injection amount integrated value becomes a relatively large value, the change amount of the fuel level sensor output is predetermined. It is necessary to determine whether it is within the normal range. Therefore, there is a problem that the frequency of failure determination is low.

  The present invention has been made paying attention to this point, and it is an object of the present invention to provide a failure diagnosis apparatus that can increase the frequency of failure determination of a fuel level sensor and can quickly detect a failure.

In order to achieve the above object, a first aspect of the present invention provides a fuel residue in a fuel tank () that is mounted on a vehicle driven by an internal combustion engine (1) and stores fuel supplied to the engine (1). In a failure diagnosis device for a fuel level sensor (11) that detects the amount, a reference fuel that sets a reference fuel level (FLVLSTC0) based on an output value (FLFLM) of the fuel level sensor after a predetermined time has elapsed since the engine was started and level setting means, a vehicle fluctuation parameter indicating a traveling state change of the vehicle (| VP-VPFLSTZ |) at a value of greater than the variation determination value (DVPFLST) Itoki, the fuel level sensor output (FLFLM) is the reference fuel Less than a value obtained by adding a predetermined fuel level change amount (FLVLSTCWD) to the level (FLVLSTC0) and the reference fuel level Determination execution means for executing determination of the sticking fault condition that is larger than a value obtained by subtracting the predetermined fuel level change amount (FLVLSTCWD) from the level (FLVLSTC0), and the number of times that the sticking fault condition is not satisfied (COKFLST) ) Is greater than or equal to a predetermined determination ratio (FLSTJUD) when the normal ratio with respect to the determination execution count (CFLSTDV) is greater than the predetermined determination ratio (FLSTJUD) , When the fuel level sensor (11) is small, the fuel level sensor (11) includes a sticking failure determination unit that determines that a fixing failure has occurred. The reference fuel level setting unit outputs an output value of the fuel level sensor when the normality determination is made. Re-establishing the reference fuel level (FLVLSTC0) based on (FLFLM) And performing.

  As the vehicle fluctuation parameter (DVHLCH), the amount of change (| VP-VPFLSTZ |) of the vehicle speed (VP) of the vehicle, the amount of change (| DSA |) of the steering angle (SA) of the steering of the vehicle, or the vehicle It is desirable to use the amount of change (| DNE |) of the rotational speed (NE) of the internal combustion engine that drives the vehicle, or the absolute value (| α |) of the acceleration of the vehicle detected by the acceleration sensor. This is because when the values of these vehicle variation parameters are large, the fuel level in the fuel tank varies greatly. Further, when the amount of change (| DSA |) of the steering angle (SA) of the steering is used as the vehicle fluctuation parameter, it is desirable to set the fluctuation determination value (DVHLCHX) according to the vehicle speed VP.

  Further, the failure diagnosis apparatus sets a determination threshold (FLVLJUDFLM) according to a travel distance measuring means for measuring the travel distance (DISTFLMK) of the vehicle and a fuel level (FLFLM) detected by the fuel level sensor (11). And a change amount (FLFLMAX−FLFLMIN) of the fuel level (FLFLM) detected by the fuel level sensor (11) when the travel distance (DISTFLMK) changes by more than the determination distance (DISTJUDFLM). It is desirable that the apparatus further comprises failure determination means for determining that the fuel level sensor (11) has failed when smaller than the determination threshold (FLVLJUDFLM).

According to the invention described in claim 1, the reference fuel level is set based on the output value of the fuel level sensor after a lapse of the start after a predetermined time of the engine, the value of the vehicle fluctuation parameter is greater than the variation determination value Itoki The sticking failure condition that the fuel level sensor output is smaller than the value obtained by adding the predetermined fuel level change amount to the reference fuel level and greater than the value obtained by subtracting the predetermined fuel level change amount from the reference fuel level is determined every predetermined time. Is called. The fuel level sensor is determined to be normal when the normal ratio of the number of times that the sticking fault condition is not satisfied is equal to or greater than the predetermined determination ratio, and when the normal ratio is smaller than the predetermined determination ratio , It is determined that a fixing failure has occurred. In the fuel tank mounted on the vehicle, the level of the fuel liquid level varies as the vehicle running state changes due to acceleration, deceleration, or turning of the vehicle. When the value is larger than the fluctuation determination value, the fluctuation of the fuel liquid level also increases. Therefore, in a state the vehicle fluctuation parameter is greater than the variation determination value, when sticking failure condition that the fuel level sensor output stays within a predetermined range around the reference fuel level is larger ratio satisfied, fuel It can be determined that the movable part of the level sensor does not move in response to the change in the fuel liquid level, that is, it can be determined that a sticking failure has occurred. This determination is difficult to perform accurately when the fuel level is nearly full or close to zero, but can always be performed when the fuel level is in any other intermediate state. Therefore, it is possible to increase the execution frequency of failure determination and quickly detect a sticking failure.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a configuration of an internal combustion engine and a fuel supply system of the internal combustion engine according to an embodiment of the present invention. An internal combustion engine (hereinafter simply referred to as “engine”) 1 has an intake pipe 2, and a fuel injection valve 6 is provided for each cylinder slightly upstream of an intake valve (not shown) of the intake pipe 2. Each fuel injection valve 6 is connected to a fuel tank 9 via a fuel supply pipe 7, and a fuel pump 8 is provided in the middle of the fuel supply pipe 7. The fuel tank 9 is provided with a fuel level sensor 11 for detecting a fuel remaining amount (hereinafter referred to as “fuel level”) LEVEL in the fuel tank. The fuel level sensor 11 is connected to an electronic control unit (hereinafter referred to as “ECU”) 5, and its detection signal is supplied to the ECU 5.

The fuel injection valve 6 is electrically connected to the ECU 5, and the valve opening time is controlled by a signal from the ECU 5.
A vehicle speed sensor 12 for detecting the vehicle speed VP of the vehicle driven by the engine 1 and an ignition switch 13 are connected. Further, an engine speed sensor, a throttle valve opening sensor, an intake pressure sensor, an engine cooling water temperature sensor, etc., not shown. Is connected to the ECU 5. The detection signals of these sensors and the switching signal of the ignition switch 13 are supplied to the ECU 5.

  The ECU 5 shapes input signal waveforms from various sensors, corrects the voltage level to a predetermined level, and converts an analog signal value into a digital signal value, a central processing unit (hereinafter referred to as “CPU”). A storage circuit for storing a calculation program executed by the CPU, a calculation result, and the like, an output circuit for supplying a drive signal to the fuel injection valve 6, and the like.

  The CPU of the ECU 5 controls the opening time of the fuel injection valve 6, that is, the amount of fuel supplied to the engine 1 in accordance with output signals from various sensors such as an engine speed sensor, an intake pressure sensor, and an engine cooling water temperature sensor. At the same time, failure diagnosis of the fuel level sensor 11 is performed.

  In the fuel level sensor 11 of the present embodiment, the output characteristic of the fuel level sensor 11 is nonlinear (with respect to the change in the remaining amount of fuel in the fuel tank) in the range where the fuel level is greater than or equal to the predetermined upper limit value FLVLRTITYH and less than or equal to the predetermined lower limit value FLVLRTTYL. When the change in the fuel level sensor output is not linear and the rate of change of the fuel level sensor output with respect to the change in the remaining amount of fuel is relatively small), and the fuel level is within a predetermined upper and lower limit range, The output characteristics of the fuel level sensor are almost linear (changes in the fuel level sensor output are linear with respect to changes in the fuel level in the fuel tank, and the rate of change in the fuel level sensor output with respect to changes in the fuel level is relatively large) ). Therefore, in the present embodiment, an improved fault diagnosis is executed focusing on this point, and the execution frequency is increased while maintaining the accuracy of the fault diagnosis.

  Furthermore, in this embodiment, when the change amount of the vehicle fluctuation parameter, specifically, the vehicle speed VP is large, and the change amount of the fuel level sensor output is smaller than the sticking determination threshold, it is determined that the fuel level sensor 11 is stuck. . When the change amount of the vehicle speed VP is large, the level of the fuel level in the fuel tank 9 fluctuates. Therefore, if the change amount of the fuel level sensor output is small at this time, it can be determined that the fuel level sensor 11 has failed. . By using this fixed failure determination together, the frequency of failure diagnosis can be further increased, and rapid failure detection becomes possible.

  FIG. 2 is a flowchart of processing for setting a determination parameter used for failure diagnosis of the fuel level sensor 11. This process is executed by the CPU of the ECU 5 every predetermined time (for example, 200 milliseconds). Specifically, the determination parameters are the vehicle travel distance (hereinafter referred to as “determination distance”) DISTJUDFLM required for executing the determination, and the change amount of the fuel level sensor output when traveling the determination distance DISTJUDFLM is within the normal range. This is a determination threshold value FLVLJUDFLM for determining whether or not there is.

  In step S11, it is determined whether the diagnosis end flag FDONEF 121B is “1” and the failure diagnosis has ended. Since the answer to step S13 is negative (NO) at first, the process proceeds to step S13 to determine whether or not the diagnosis permission flag FFLVLCND is “1”. Immediately after the engine 1 is started, since FFLVLCND = 0, this processing is immediately terminated. When a predetermined time (for example, 10 seconds) elapses after the engine is started, the diagnosis permission flag FFLVLCND is set to “1”. Thereafter, the process proceeds from step S13 to step S14, and it is determined whether or not the initialization completion flag FF121BINI is “1”.

  Initially, since FF121BINI = 0, the process proceeds to step S15, and both the initial fuel level FLFLM0 and its previous value FLFLM0Z are set to the fuel level FLFLM at that time. The fuel level FLFLM is calculated by subjecting the output LEVEL of the fuel level sensor 11 to a smoothing process that excludes short cycle fluctuations. In the subsequent step S16, both the reset request flag FRESET121 and the initialization completion flag FF121BINI are set to “1”, and this process ends. When the reset request flag FRESET121 is set to “1”, the travel distance DISTFLMK and the maximum value FLFLMAX and the minimum value FLFLMIN of the fuel level FLFLM are reset in the process of FIG. 3 (see steps S44, S56, and S57). .

  After step S16 is executed, the answer to step S14 is affirmative (YES), and the process proceeds to step S17. In step S17, it is determined whether or not the setting completion flag FF121BSET is “1”. The setting completion flag FF121BSET is set to “1” in step S30 when the determination parameter setting is completed. Therefore, first, FF121BSET = 0, and the process proceeds to step S18.

  In step S18, the previous value FLFLM0Z of the initial fuel level is set to the current value FLFLM0, and in step S19, the initial fuel level FLFLM0 is set to the current fuel level FLFLM. In step S20, it is determined whether or not the initial fuel level FLFLM0 is equal to or higher than a predetermined lower limit value FLVLRTYL (for example, a value corresponding to 15% of the fuel tank capacity). If the answer is affirmative (YES), it is further determined whether or not the initial fuel level FLFLM0 is equal to or lower than a predetermined upper limit value FLVLRTYH (for example, a value corresponding to 85% of the fuel tank capacity) (step S21).

  When the answer to steps S20 and S21 is both affirmative (YES), that is, when the initial fuel level FLFLM0 is within the range of the predetermined upper and lower limit values, the previous value FLFLM0Z of the initial fuel level is less than or equal to the predetermined upper limit value FLVLRTYH. Whether or not (step S22). If the answer is affirmative (YES), it is further determined whether or not the previous value FLFLM0Z of the initial fuel level is equal to or greater than a predetermined lower limit value FLVLTYL (step S23).

  If the answer to step S22 or S23 is negative (NO), and the initial fuel level at the start of the previous engine operation is higher than the predetermined upper limit value FLVLRTYH, or lower than the predetermined lower limit value FLVLRTIL, that is, the initial fuel level is When shifting from outside the predetermined upper and lower limit values to within the range, the reset request flag FRESET121 is set to “1” (step S24), and then the process proceeds to step S25. On the other hand, if the answer to steps S22 and S23 is both affirmative (YES) and the initial fuel level is within the predetermined upper and lower limits at the start of the previous engine operation and the start of the current engine operation, immediately Proceed to step S25.

  In step S25, the determination threshold value FLVLJUDFLM is set to the first predetermined value FLVLJUDFLMR. In step S26, the determination distance DISTJUDFLM is set to a first predetermined distance value DISTJUDFLMR (for example, 30 km). Next, the setting completion flag FF121BSET is set to “1” (step S30), and this process ends.

  If the answer to step S20 or S21 is negative (NO) and the current initial fuel level FLFLM0 is not within the range of the predetermined upper and lower limit values, the determination threshold value FLVLJUDFLM is set to a second value greater than the first predetermined value FLVLJUDFLMR. The predetermined value FLVLJUDFLMN is set (step S28), and the determination distance DISTJUDFLM is set to a second predetermined distance value DISTJUDFLMN (for example, 200 km) larger than the first predetermined distance DISTJUDFLMR (step S29). Thereafter, the process proceeds to step S30.

  After the setting completion flag FF121BSET is set to “1”, the answer to step S17 becomes affirmative (YES), and the process proceeds to step S27. In step S27, it is determined whether or not the fuel level FLFLM is lower than a predetermined lower limit value FLVLRTYL. If the answer is affirmative (YES), the process proceeds to step S28, and if FLFLM ≧ FLVLRTYL, the process is immediately terminated. That is, after the determination parameter is set, when the fuel level FLFLM decreases and becomes lower than the predetermined lower limit value FLVLRTTYL, the determination threshold value FLVLJUDFLM is changed to the second predetermined value FLVLJUDFLMN, and the determination distance DISTJUDFLM is changed to the second value. Change to the predetermined distance value DISTJUFDLMN.

  When it is determined in FIG. 3 described later that the fuel level sensor 11 has failed and the diagnosis end flag FDONEF 121B is set to “1” (step S54), the process proceeds from step S11 to step S12, and the initialization completion flag FF121BINI and Both setting completion flags FF121BSET are set to “0”.

FIG. 3 is a flowchart of a process for determining a failure of the fuel level sensor 11. This process is executed by the CPU of the ECU 5 every predetermined time (for example, 200 milliseconds).
In step S41, it is determined whether or not the diagnosis end flag FDONEF 121B is “1”. Since this answer is negative (NO) at first, it is determined whether or not the setting completion flag FF121BSET is “1” (step S42). While this answer is negative (NO), this process is immediately terminated. When the setting completion flag FF121BSET is set to “1”, the process proceeds to step S43, and it is determined whether or not the reset completion flag FRESET121DN is “1”. Initially, the answer to step S44 is negative (NO), so the process proceeds to step S44 to determine whether or not the reset request flag FRESET121 is “1”.

  When FRESET121 = 0 and no reset request is made, it is determined whether or not the travel distance DISTFLMK of the vehicle is greater than or equal to the determination distance DISTJUDFLM (step S45). If this answer is negative (NO), it is determined whether or not the fuel cut flag FFC is "1" (step S46). The fuel cut flag FFC is set to “1” when the fuel supply to the engine 1 is cut off.

When FFC = 0 and fuel is supplied in step S46, the distance traveled during the execution cycle DT is calculated by multiplying the vehicle speed VP by the execution cycle DT of this processing according to the following equation (1). DISTDT is calculated (step S47).
DISTDT = VP × DT (1)
In step S48, the travel distance DISTFLMK is calculated by integrating the distance DISTDT by the following equation (2).
DISTFLMK = DISTFLMK + DISDT (2)

On the other hand, if FFC = 1 and fuel cut operation is being performed in step S46, the process immediately proceeds to step S49.
In step S49, the larger one of the fuel level FLFLM and the maximum value FLFLMAX is selected by the following equation (3), and the maximum value FLFLMAX of the fuel level FLFLM is updated. In step S50, the smaller one of the fuel level FLFLM and the minimum value FLFLMIN is selected by the following equation (4), and the minimum value FLFLMIN of the fuel level FLFLM is updated. Thereafter, this process is terminated.
FLFLMAX = MAX (FLFLMAX, FLFLM) (3)
FLFLMIN = MIN (FLFLMIN, FLFLM) (4)

  When the travel distance DISTFLMK increases and reaches the determination distance DISTJUDFLM, the process proceeds from step S45 to step S52, and it is determined whether or not the value obtained by subtracting the minimum value FLFLMIN from the maximum value FLFLMAX is equal to or greater than the determination threshold FLVLJUDFLM. If this answer is negative (NO) and the change amount of the fuel level sensor output is smaller than the determination threshold value FLVLJUDFLM, it is determined that the fuel level sensor 11 has failed, and the normal flag FOKF 121B is set to “0”. At the same time, the failure flag FFSDF121B is set to “1” (step S53). Next, the diagnosis end flag FDONEF 121B is set to “1” (step S54), and this process ends. After the diagnosis end flag FDONEF 121B is set to “1”, the answer to step S41 becomes affirmative (YES), and this process is immediately ended.

  If (FLFLMAX−FLFLMIN) is greater than or equal to the determination threshold FLVLJUDFLM in step S52, the fuel level sensor 11 determines that it is normal and sets the normal flag FOKF 121B to “1” (step S55). Further, the travel distance DISTFLMK is reset to “0” (step S56), and the maximum value FLFLMAX and the minimum value FLFLMIN are both set to the fuel level FLFLM at that time (step S57). Thereafter, this process is terminated. When the normal determination is made in this way, the diagnosis end flag FDONEF 121B is not set to “1”, the travel distance DISTFLMK, the maximum value FLFLMAX, and the minimum value FLFLMIN are reset, and the travel distance DISTFLMK reaches the determination distance DISTJUDFLM. A failure determination is performed.

  If the reset request flag FRESET121 is set to “1” in step S16 or S24 of FIG. 2, the answer to step S44 is affirmative (YES), the process proceeds to step S51, and the reset completion flag FRESET121DN is set to “1”. The process proceeds to step S56. That is, the travel distance DISTFLMK, the maximum fuel level FLFLMAX, and the minimum FLFLMIN are reset in response to the reset request. After the reset completion flag FRESET121DN is set to “1”, the answer to step S43 is affirmative (YES), and the process immediately proceeds from step S43 to step S45.

  As described above, according to the processing shown in FIG. 2 and FIG. 3, the determination threshold FLVLJUDFLM is the first when the fuel level is within the predetermined upper and lower limit values according to the parameters (FLFLM0, FLFLM0Z, FLFLM) indicating the fuel level. And the determination distance DISTJUDFLM is set to the first predetermined distance value DISTJUDFMLMR. On the other hand, when the fuel level is outside the range of the predetermined upper and lower limit values, the determination threshold value FLVLJUDFLM is set to a second predetermined value FLVLJUDFLMN that is greater than the first predetermined value FLVLJUDFLMR, and the determination distance DISTJUDFLM is the first predetermined distance value DISTJUDFLMR A larger second predetermined distance value DISTJUFDLMN is set. Then, depending on whether or not the amount of change in the detected fuel level when the vehicle travels the determination distance DISTJUDFLM, specifically, the difference between the maximum value FLFLMAX and the minimum value FLFLMIN (FLFLMAX−FLFLMIN) is greater than or equal to the determination threshold value FLVLJUDFLM. A failure of the fuel level sensor is determined. This is because, when the fuel level is within the range of the predetermined upper and lower limit values, the characteristics of the fuel level sensor 11 are substantially linear, and the change amount of the sensor output with respect to the change in the remaining amount of fuel is relatively large, so the determination distance DISTJUDFLM It is noted that accurate determination is possible even if is short. Therefore, according to the processing shown in FIG. 2 and FIG. 3, the frequency of fault diagnosis can be increased without reducing the accuracy of fault diagnosis.

FIG. 4 and FIG. 5 are flowcharts of processing for determining the sticking failure of the fuel level sensor 11. This process is executed by the CPU of the ECU 5 every predetermined time (for example, 200 milliseconds).
In step S61, it is determined whether or not the diagnosis end flag FDONEF 121B is “1”. If the answer to step S61 is affirmative (YES), the process immediately ends. When FDONEF121B = 0, it is determined whether or not the diagnosis permission flag FFLVLCND is “1” (step S62). While FFLVLCND = 0, the process immediately proceeds to step S81. When the diagnosis permission flag is set to “1”, the process proceeds to step S63 to determine whether or not the reference value storage flag FFLVLSTC0 is “1”. Initially, this answer is negative (NO), so the current fuel level FLFLM is set to the reference fuel level FLVLSTC0 (step S64), and then the reference value storage flag FFLVLSTC0 is set to “1” (step S65). . After the reference value storage flag FFLVLSTC0 is set to “1”, the process immediately proceeds from step S63 to step S66 (FIG. 5).

  In step S66 (FIG. 5), it is determined whether or not the reference fuel level FLVLSTC0 is equal to or higher than a predetermined lower limit value FLVLSTCL (for example, a value corresponding to 15% of the fuel tank capacity). If the answer is affirmative (YES), it is further determined whether or not the reference fuel level FLVLSTC0 is equal to or less than a predetermined upper limit value FLVLSTCH (for example, a value corresponding to 85% of the fuel tank capacity) (step S67). In the present embodiment, the predetermined upper and lower limit values FLVLSTCH and FLVLSTCL are set to the same values as the predetermined upper and lower limit values FLVLRTYH and FLVLRTLL used in the processing of FIG.

If the answer to step S66 or S67 is negative (NO), that is, if the reference fuel level FLVLSTC0 is outside the range of the predetermined upper and lower limits FLVLSTCH, FLVLSTCL, the process immediately proceeds to step S81.
When the answer to steps S66 and S67 is both affirmative (YES), that is, when the reference fuel level FLVLSTC0 is within the predetermined upper and lower limits FLVLSTCH and FLVLSTCL, the value of the determination number counter COKFLSTDV is equal to the predetermined determination number CTFLSTDV ( For example, it is determined whether it is 500) or more (step S68). Initially, the answer to step S69 is negative (NO), and the process proceeds to step S69 to determine whether or not the value of the thinning counter COFLVLSTC is “0” (step S68). Initially, the answer is affirmative (YES), and the process proceeds to step S71.

  In step S71, the absolute value of the difference between the vehicle speed VP and the previous vehicle speed VPFLSTZ (the vehicle speed VP detected during the previous execution of this process) (hereinafter referred to as “vehicle speed change amount”) is the vehicle speed fluctuation determination value DVPFLST (eg, 0. 0). It is determined whether it is 5 km / h) or more. If the answer is no (NO), the process immediately proceeds to step S80.

  When the absolute value of the vehicle speed change amount | VP−VPFLSTZ | is equal to or greater than the vehicle speed fluctuation determination value DVPFLST, the value of the determination number counter COKFLSTDV is incremented by “1” (step S72), and the fuel level FLFLM is the reference fuel level. It is determined whether or not the value is equal to or greater than a value obtained by adding a predetermined fuel level change amount FLVLSTCWD to FLVLSTC0 (step S73). If this answer is negative (NO), it is further determined whether or not the fuel level FLFLM is equal to or less than a value obtained by subtracting the predetermined fuel level change amount FLVLSTCWD from the reference fuel level FLVLSTC0 (step S74).

  If the answer to step S73 or S74 is affirmative (YES) and the fuel level FLFLM changes by a predetermined fuel level change amount FLVLSTCWD or more, the value of the OK counter COKFLST is incremented by “1” (step S75), and step S80. Proceed to That is, when the vehicle speed VP changes greatly and the fuel level FLFLM changes by a predetermined fuel level change amount FLVLSTCWD, it is determined that the fuel level sensor 11 is likely to be normal, and the value of the OK counter COKFLST is incremented.

On the other hand, if the answer to steps S73 and S74 is negative (NO) and the absolute value of the fuel level change amount | FLFLM−FLVLSTCWD | is smaller than the predetermined fuel level change amount FLVLSTCWD, the value of the OK counter COKFLST is incremented. If not, the process immediately proceeds to step S80.
In step S80, the thinning counter COFLVLSTC is set to a predetermined number of times CTOFLVLSTC (for example, 4). Thereafter, the process proceeds to step S81, the previous vehicle speed VPFLSTZ is set to the vehicle speed VP at that time, and this process is terminated.

  After executing step S80, the answer to step S69 is negative (NO), and the value of the thinning counter COFLVLSTC is decremented by “1” (step S70). Thereafter, this process is terminated. Step S70 is repeatedly executed, and when the value of the thinning counter COFLVLSTC becomes “0”, the process proceeds from step S69 to step S71. Accordingly, steps S71 to S75 are executed at a rate of once every time this process is executed (CTOFLVLSTC + 1) times by steps S69, S70, and S80.

  When the value of the determination counter COKFLSTDV (the number of executions of steps S72 to S74) reaches the predetermined determination number CTFLSTDV, the process proceeds from step S68 to step S76, and the ratio COKFLST / CFLSTDV of the value of the OK counter COKFLST to the predetermined determination number CTFLSTDV is It is determined whether or not the determination ratio is FLSTJUD (for example, 0.4) or more. If this answer is negative (NO), it is determined that the fuel level sensor 11 has a sticking fault, and the sticking fault flag FFLSTNG is set to "1" (step S79). Thereafter, the process proceeds to step S80.

  If COKFLST / CFLSTDV ≧ FLSTJUD in step S76, it is determined that the fuel level sensor 11 is normal, the non-sticking flag FFLSTOK is set to “1”, and the reference value storage flag FFLVLSTC0 is set to “0” (step S76). S77). Next, both the values of the determination number counter COKFLSTDV and the OK counter COKFLST are set to “0” (step S78), and the process proceeds to step S80.

  As described above, according to the processing of FIGS. 4 and 5, when the absolute value | VP−VPFLSTZ | of the vehicle speed change amount is equal to or larger than the vehicle speed fluctuation determination value DVPFLST, the absolute value of the fuel level change amount | FLFLM−FLVLSTCWD | Is equal to or greater than the predetermined fuel level change amount FLVLSTCWD, the OK counter COKFLST is incremented, and when the ratio COKFLST / CFLSTDV of the value of the OK counter COKFLST to the determination execution count CTFLSTDV is smaller than the determination ratio FLSTJUDCOKFLST, the fuel level sensor 11 is fixed. It is determined that a failure has occurred. However, this determination is not performed when the fuel level FLFLM is outside the range of the predetermined upper and lower limits FLVLSTCH and FLVLSTCL (in the non-linear region). This is because in the non-linear region, the amount of change in the fuel level sensor output with respect to the change in the fuel liquid level is small, so that accurate determination cannot be made. That is, the accurate determination can be performed by executing the sticking determination only when the fuel level FLFLM is within the range of the predetermined upper and lower limits FLVLSTCH and FLVLSTCL.

In the present embodiment, the ECU 5 constitutes a reference fuel level setting unit, a determination execution unit, a normality determination unit, and a sticking failure determination unit. Specifically, Steps S62 to S65 in FIG. 4 and Step S77 in FIG. 5 correspond to reference fuel level setting means, Steps S71 to S74 in FIG. 5 correspond to determination execution means, and Steps S75 to S77 are normal determinations. Steps S76 and S79 correspond to fixing failure determination means. Further, the vehicle speed sensor 12 and the ECU 5 constitute a travel distance measuring means. The ECU 5 constitutes a travel distance calculating means, a determination threshold setting means, and a failure determination means. Specifically, steps S47 and S48 in FIG. 3 correspond to travel distance calculation means, the processing in FIG. 2 corresponds to determination threshold setting means, and steps S45 and S52 to S55 in FIG. 3 correspond to failure determination means. To do.

(Modification)
FIG. 6 is a flowchart of processing in which step S71 in FIG. 5 is changed to step S71a and step S80 is deleted. The flowchart shown in FIG. 6 is connected to the flowchart of FIG. 4 similarly to the flowchart of FIG. In step S71a, it is determined whether or not the vehicle variation parameter DVHLCH is greater than or equal to the variation determination value DVHLCHX. When the vehicle fluctuation parameter DVHLCH is equal to or greater than the fluctuation determination value DVHLCHX, the process proceeds to step S72, and when the answer to step S71a is negative (NO), the process proceeds to step S80.

  In the above-described embodiment, the absolute value of the vehicle speed change amount is used as the vehicle fluctuation parameter DVHLCH. Instead, a steering angle sensor for detecting the steering angle SA of the steering of the vehicle is provided, and the absolute value of the change amount DSA (= SA (k) −SA (k−1)) of the steering angle SA is determined based on vehicle fluctuations. The parameter DVHLCH may be used. Here, “k” is a control time discretized in the execution cycle of the process of FIG. In that case, the variation determination value DVHLCHX is set to a smaller value as the vehicle speed VP increases. For example, when VP = 50 km / h, the variation determination value DVHLCHX is set to a value corresponding to 45 degrees / second, and when VP = 100 km / h, it is set to a value corresponding to 10 degrees / second. . As a result, it is possible to accurately determine the occurrence of fluctuations in the fuel level due to the change in the steering angle SA, and to accurately determine the sticking failure of the fuel level sensor 11.

  Further, an engine speed sensor for detecting the rotation speed (rotation speed) of the engine 1 is provided, and a change amount DNE (=) corresponding to a one-time differential value of the engine speed NE is set as the vehicle speed fluctuation parameter DVHLCH in step S71a of FIG. NE (k) −NE (k−1)) or the absolute value of the parameter DDNE (= DNE (k) −DNE (k−1)) corresponding to the twice differential value may be used. However, in this case, it is a precondition that the gear ratio of the transmission does not change.

  Further, an acceleration sensor is provided in the vehicle, and the absolute value of acceleration α detected by the acceleration sensor or the absolute value of Dα (= α (k) −α (k−1)) corresponding to the differential value of acceleration is calculated by It may be used as the fluctuation parameter DVHLCH.

  In the above-described embodiment, the OK counter COKFLST is used to determine that the fixing failure has occurred when the ratio of the value of the OK counter COKFLST to the number of determination executions is smaller than the determination ratio FLSTJUD. Instead, the ratio of the number of times that the fuel level sensor output change amount (| FLFLM−FLVLSTC0 |) is determined to be smaller than the predetermined fuel level change amount FLVLSTCWD to the determination execution number CTFLSTDV is calculated, and this ratio is the predetermined failure determination ratio. When larger than (1-FLSTJUD), it may be determined that a fixing failure has occurred.

  In addition, when both the answers of steps S73 and S74 in FIG. 5 are negative (NO), it may be determined that a fixing failure has occurred immediately. However, when such a method is adopted, erroneous determination is likely to occur. Therefore, it is desirable to use the ratio of the number of normal determinations or the ratio of the number of failure determinations as in the above-described embodiment.

  In the above-described embodiment, the fuel level FLFLM is within the predetermined upper and lower limit values FLVLRTHH and FLVLRTTYL according to the fuel level FLFLM detected by the fuel level sensor 11, and the fuel level FLFLM is the predetermined upper / lower limit value FLVLRTYH. The determination threshold value FLVLJUDFLM and the determination distance DISTJUDFLM are set in correspondence with when the value is outside the range of FLVLTYL. However, the present invention is not limited to this, and the range corresponding to the fuel level is set to 3 according to the characteristics of the fuel level sensor. Two or more may be set, and the determination threshold FLVLJUDFLM and the determination distance DISTJUDFLM may be set corresponding to each range.

An odometer (odometer) may be used as the mileage measuring means.
The present invention can also be applied to failure diagnosis of a fuel level sensor attached to a fuel tank that supplies fuel to an engine for a marine propulsion device such as an outboard motor having a vertical crankshaft.

1 is a diagram illustrating a configuration of an internal combustion engine according to an embodiment of the present invention and a fuel supply system of the internal combustion engine. It is a flowchart of the process which sets the parameter used for the failure determination of the fuel level sensor shown in FIG. It is a flowchart of the process which performs failure determination of the fuel level sensor shown in FIG. It is a flowchart of the process which performs sticking determination of the level sensor shown in FIG. It is a flowchart of the process which performs sticking determination of the level sensor shown in FIG. It is a flowchart of the modification of the process shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 5 Electronic control unit (sticking failure determination means, travel distance measurement means, travel distance calculation means, determination threshold setting means, failure determination means)
9 Fuel tank 11 Fuel level sensor 12 Vehicle speed sensor (travel distance measuring means)

Claims (1)

In a failure diagnosis device for a fuel level sensor that is mounted on a vehicle driven by an internal combustion engine and detects the remaining amount of fuel in a fuel tank that stores fuel to be supplied to the engine,
A reference fuel level setting means for setting a reference fuel level based on an output value of the fuel level sensor after a predetermined time has elapsed after starting of the engine;
In the value of the vehicle fluctuation parameter indicating a variation in the traveling state of the vehicle is greater than the variation determination value Itoki, less than the value the fuel level sensor output is obtained by adding a predetermined fuel level change amount to the reference fuel level, and the reference Determination execution means for executing a determination of the sticking failure condition that is larger than a value obtained by subtracting the predetermined fuel level change amount from the fuel level at predetermined time intervals;
Normal determination means for determining that the fuel level sensor is normal when a normal ratio of the number of times that the sticking failure condition is not satisfied to a determination execution number is equal to or greater than a predetermined determination ratio;
When the normal ratio is smaller than the predetermined determination ratio, it is provided with a fixing failure determination means for determining that a fixing failure of the fuel level sensor has occurred ,
The fuel level sensor failure diagnosis apparatus, wherein the reference fuel level setting means resets the reference fuel level based on an output value of the fuel level sensor when the normality determination is made .

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