JP2006214390A - Failure diagnosing device for fuel level sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a failure diagnosing device capable of accurately diagnosing failure of a fuel level sensor at high frequency. <P>SOLUTION: In the case wherein a difference between the maximum value FLFLMAX and the minimum value FLFLMIN of detected fuel level FLFLM within a determination period is smaller than a determination threshold value FLVLJUDFLM when travelling distance DISTFLMK of a vehicle reaches the determination distance DISTJUDFLM, failure of the fuel level sensor is determined (S45, S52 and S53). The determination threshold value FLVLJUDFLM is set in response to the fuel level FLFLM. <P>COPYRIGHT: (C)2006,JPO&NCIPI

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

  The output characteristics of the fuel level sensor are set to non-linear characteristics with respect to changes in the remaining fuel amount when the fuel tank is nearly full and the remaining fuel amount is small. That is, the change amount of the fuel level sensor output corresponding to the change of the remaining fuel amount is set to be smaller than, for example, a state where the remaining fuel amount is about half. Therefore, in order to make an accurate determination, it is necessary to set the predetermined integrated value to a large value, and there is a problem that the frequency of performing fault diagnosis is reduced.

  This invention is made paying attention to this point, and it aims at providing the failure diagnosis apparatus which can perform the failure diagnosis of a fuel level sensor correctly and frequently.

  In order to achieve the above object, an invention according to claim 1 is provided in a fuel tank (9) which is mounted on a vehicle driven by an internal combustion engine (1) and stores fuel supplied to the engine (1). In accordance with a fuel distance sensor that detects the travel distance (DISTFLMK) of the vehicle and a fuel level (FLFLM) detected by the fuel level sensor (11). A determination threshold value setting means for setting a determination threshold value (FLVLJUDFLM) and a fuel level (FLFLM) detected by the fuel level sensor (11) when the travel distance (DISTFLMK) changes by more than the determination distance (DISTJUDFLM). The change amount (FLFLMAX−FLFLMIN) is smaller than the determination threshold (FLVLJUDFLM) Itoki, characterized by comprising a a determination means the fuel level sensor (11) is faulty.

According to a second aspect of the present invention, in the failure diagnosis apparatus for a fuel level sensor according to the first aspect, the determination threshold value setting means sets at least the determination threshold value (FLVLJUDFLM) in accordance with the detected fuel level (FLFLM). Two predetermined values (FLVLJUDFLMR, FLVLJUDFLMN) are set, and the first predetermined value (FLVLJUDFLMR) is applied in a region where the output characteristic of the fuel level sensor (11) is substantially linear, and the second predetermined value (FLVLJUDFLMN) ) Is applied in a region where the output characteristic of the fuel level sensor (11) is nonlinear.
The second predetermined value (FLVLJUDFLMN) is set to a value larger than the first predetermined value (FLVLJUDFLMR).

  Further, it is desirable to further include determination distance setting means for setting the determination distance (DISTJUDFLM) in accordance with the fuel level (FLFLM) detected by the fuel level sensor (11). The determination distance setting means sets the determination distance (DISTJUDFLM) to at least two predetermined distance values (DISTJUDFMLMR, DISTJUDFLMN) according to the detected fuel level (FLFLM), and the first predetermined distance value (DISTJUDFLMR) is And the second predetermined distance value (DISTJUDFLMN) is applied in a region where the output characteristic of the fuel level sensor (11) is non-linear. It is desirable. Here, the second predetermined distance value (DISTJUDFLMN) is set to a value larger than the first predetermined distance value (DISTJUDFLMR).

  The travel distance measuring means includes a vehicle speed sensor (12) for detecting the travel speed (VP) of the vehicle, and a travel distance calculating means for calculating the travel distance (DISTFLMK) by integrating the detected vehicle speed (VP). The travel distance calculating means preferably interrupts the calculation of the travel distance (DISTFLMK) during the fuel supply stop operation period in which the fuel supply to the engine is stopped.

  The determination threshold value setting means sets the determination threshold value (FLVLJUDFLM) to the first predetermined value (FLVLJUDFLMR) when the fuel level is within a range of predetermined upper and lower limit values (FLVLRTTYH, FLVLRTTYL). When the fuel level is outside the predetermined upper and lower limit values (FLVLRTTYH, FLVLRTTYL), it is desirable to set the determination threshold value (FLVLJUDFLM) to the second predetermined value (FLVLJUDFLMN). The determination distance setting means sets the determination distance (DISTJUDFLM) to the first predetermined distance value (DISTJUDFLMR) when the fuel level is within a predetermined upper / lower limit value (FLVLRTTYH, FLVLRTTYL). When the fuel level is outside the predetermined upper and lower limit values (FLVLRTTYH, FLVLRTTYL), it is desirable to set the determination distance (DISTJUDFLM) to the second predetermined distance value (DISTJUDFLMN).

  Further, when the determination threshold value changing unit changes the determination threshold value (FLVLJUDFLM) to a smaller value (FLVLJUDFLMR), the determination threshold value setting unit executes the change when the vehicle is stopped, and sets the determination threshold value (FLVLJUDFLM) to a larger value (FLVLJUDFLMN). When changing to (), it is desirable to execute the change immediately. Further, when the determination distance setting means changes the determination distance (DISTJUDFLM) to a smaller value (DISTJUDFLMR), the determination distance setting means executes the change when the vehicle is stopped, and sets the determination distance (DISTJUDFLM) to a larger value (DISTJUDFLMN). When changing to, it is desirable to execute the change immediately.

  According to the first aspect of the present invention, the determination threshold is set according to the fuel level detected by the fuel level sensor, and the fuel level detected by the fuel level sensor when the vehicle travel distance changes by more than the determination distance. Is not changed more than the determination threshold, it is determined that the fuel level sensor has failed. Therefore, for example, the fuel remaining in the fuel tank is in a very low or very high area (hereinafter referred to as “non-linear area”), or the fuel remaining in a non-non-linear area (hereinafter referred to as “linear area”). By appropriately changing the determination threshold according to whether or not there is, accurate failure diagnosis can be performed, and the frequency of failure diagnosis can be increased.

  According to the second aspect of the present invention, the determination threshold is set to the first predetermined value or the second predetermined value according to the detected fuel level, and the first predetermined value is the output of the fuel level sensor. The second predetermined value is applied in a non-linear region where the output characteristic of the fuel level sensor is non-linear. In the linear region, by using a relatively small determination threshold, the determination distance can be shortened, and the execution frequency can be increased while maintaining the accuracy of failure diagnosis.

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.

  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 value 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 manner, 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 has traveled 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 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 fuel amount 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.

  4 to 10 are diagrams for explaining the timing when the determination parameters (the determination threshold FLVLJUDFLM and the determination distance DISTJUDFLM) are changed, and the timing when the travel distance DISTFLLMK, the maximum value FLFLMAX and the minimum value FLFLMIN of the fuel level are reset. It is a time chart. In these drawings, changes in the fuel level FLFLM, the travel distance DISTFLMK, and the vehicle speed VP are shown in order from the top. An operation example is shown in which the previous operation period is started at time t1 and the current operation period is started at time t2.

  FIG. 4 shows an example in which both the initial fuel level FLFLM0Z in the previous operation period and the initial fuel level FLFLM0 in the current operation period are higher than the predetermined upper limit value FLVLRTYH. In this example, the determination threshold value FLVLJUDFLM is set to the second predetermined value FLVLJUDFLMN, and the determination distance DISTJUDFLM is set to the second predetermined distance value DISTJUDFLMN.

  FIG. 5 shows an example in which the initial fuel level FLFLM0Z in the previous operation period is higher than the predetermined upper limit value FLVLRTYH, and the initial fuel level FLFLM0 in the current operation period is within the range of the predetermined upper and lower limit values. In this example, the fuel level FLFLM falls below the predetermined upper limit value FLVLRTTYH during the previous operation period, but the determination threshold value FLVLJUDFLM is maintained at the second predetermined value FLVLJUDFLMN, and the determination distance DISTJUDFLM is maintained at the second predetermined distance value DISTJUDFLMN. Is done. This is because the case where the fuel level FLFLM falls below the predetermined upper limit value FLVLRTYH due to the fluctuation of the fuel level during traveling of the vehicle is taken into consideration. That is, the determination distance DISTJUDFLM and the determination threshold value FLVLJUDFLM are changed in the decreasing direction at the start of the next operation.

  At the start t2 of the current operation period, since the initial fuel level FLFLM0 is lower than the predetermined upper limit value FLVLRTTYH, the reset request flag FRESET121 is set to “1” (step S24), the travel distance DISTFLMK, the maximum fuel level FLFLMAX In addition, the minimum value FLFLMIN is reset, the determination threshold value FLVLJUDFLM is changed to the first predetermined value FLVLJUDFLMR, and the determination distance DISTJUDFLM is changed to the first predetermined distance value DISTJUDFLMR.

  When the determination distance DISTJUDFLM is changed from the second predetermined distance value DISTJUDFLMN to the first predetermined distance value DISTJUDFLMR, that is, when the determination distance DISTJUDFLM is shortened, the travel distance DISTFLMK calculated so far is reset and newly set. It is necessary to calculate the travel distance DISTFLMK. This is because the travel distance DISTFLMK may exceed the determination distance DISTJUDFLM when the determination distance DISTJUDFLM is shortened unless the determination distance is reset.

  FIG. 6 shows an example in which the initial fuel level FLFLM0Z in the previous operation period and the initial fuel level FLFLM0 in the current operation period are both within the predetermined upper and lower limit values. In this example, the determination threshold value FLVLJUDFLM is set to the first predetermined value FLVLJUDFLMR, and the determination distance DISTJUDFLM is set to the first predetermined distance value DISTJUDFLMR.

  FIG. 7 shows that both the initial fuel level FLFLM0Z in the previous operation period and the initial fuel level FLFLM0 in the current operation period are within the predetermined upper and lower limits, and the fuel level reaches the predetermined lower limit FLVLTYL at time t3 during the current operation period. Below is an example. In this example, initially, the determination threshold value FLVLJUDFLM is set to the first predetermined value FLVLJUDFLMR, and the determination distance DISTJUDFLM is set to the first predetermined distance value DISTJUDFLMR, but the determination threshold value FLVLJUDFLM is set to the second predetermined value at time t3. The value FLVLJUDFLMN is changed, and the determination distance DISTJUDFLM is changed to the second predetermined distance value DISTJUDFLMN. As described above, the determination threshold FLVLJUDFLM and the determination distance DISTJUDFLM are changed in the increasing direction immediately when the fuel level FLFLM falls below the predetermined lower limit value FLVLRTTYL. Thereby, it is possible to prevent erroneous determination when the fuel level FLFLM shifts from the linear region of the fuel level sensor characteristic to the nonlinear region.

  FIG. 8 shows an example in which both the initial fuel level FLFLM0Z in the previous operation period and the initial fuel level FLFLM0 in the current operation period are lower than the predetermined lower limit value FLVLTYL. In this example, the determination threshold value FLVLJUDFLM is set to the second predetermined value FLVLJUDFLMN, and the determination distance DISTJUDFLM is set to the second predetermined distance value DISTJUDFLMN.

  FIG. 9 shows an example in which the initial fuel level FLFLM0Z in the previous operation period is lower than the predetermined lower limit value FLVLRTYL, and the initial fuel level FLFLLM0 in the current operation period is within the range of the predetermined upper and lower limit values due to refueling. At time t2, the reset request flag FRESET121 is set to “1”, so that the travel distance DISTFLMK, the maximum value FLFLMAX of the fuel level, and the minimum value FLFLMIN are reset, and the determination threshold value FLVLJUDFLM is changed to the first predetermined value FLVLJUDFLMR Then, the determination distance DISTJUDFLM is changed to the first predetermined distance value DISTJUDFLMR.

  FIG. 10 shows an example in which the initial fuel level FLFLM0Z in the previous operation period is lower than the predetermined lower limit value FLVLTYL, and the initial fuel level FLFLLM0 in the current operation period is higher than the predetermined upper limit value FLVLTYH due to refueling. In this example, since the reset request flag FRESET121 is not set to “1” at time t2, the mileage DISTFLMK, the maximum value FLFLMAX of the fuel level, and the minimum value FLFLMIN are not reset, and the determination threshold FLVLJUDFLM is the second predetermined value FLVLJUDFLMN And the determination distance DISTJUDFLM is maintained at the second predetermined distance value DISTJUDFLMN.

  In the present embodiment, the vehicle speed sensor 12 and the ECU 5 constitute travel distance measuring means. Further, the ECU 5 constitutes a travel distance calculation means, a determination threshold setting means, a determination means, and a determination distance setting means. Specifically, steps S47 and S48 in FIG. 3 correspond to travel distance calculation means, the processing in FIG. 2 corresponds to determination threshold value setting means and determination distance setting means, and steps S45 and S52 to S55 in FIG. It corresponds to the determination means.

The present invention is not limited to the embodiment described above, and various modifications can be made. For example, in the above-described embodiment, when the fuel level is within the predetermined upper / lower limit value range and when the fuel level is outside the predetermined upper / lower limit value range according to the fuel level FLFLM detected by the fuel level sensor. The determination threshold value FLVLJUDFLM and the determination distance DISTJUDFLM are set in correspondence with the above. However, the present invention is not limited to this, and three or more ranges corresponding to the fuel level are set according to the characteristics of the fuel level sensor. The determination threshold FLVLJUDFLM and the determination distance DISTJUDFLM may be set in correspondence with the above.
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 time chart for demonstrating the setting of the parameter used for a failure determination. It is a time chart for demonstrating the setting of the parameter used for a failure determination. It is a time chart for demonstrating the setting of the parameter used for a failure determination. It is a time chart for demonstrating the setting of the parameter used for a failure determination. It is a time chart for demonstrating the setting of the parameter used for a failure determination. It is a time chart for demonstrating the setting of the parameter used for a failure determination. It is a time chart for demonstrating the setting of the parameter used for a failure determination.

Explanation of symbols

1 Internal combustion engine 5 Electronic control unit (travel distance measuring means, travel distance calculating means, determination threshold setting means, determination means, determination distance setting means)
9 Fuel tank 11 Fuel level sensor 12 Vehicle speed sensor (travel distance measuring means)

Claims (2)

In a failure diagnosis device for a fuel level sensor that is mounted on a vehicle driven by an internal combustion engine and detects a remaining amount of fuel in a fuel tank that stores fuel supplied to the engine,
Mileage measuring means for measuring the mileage of the vehicle;
Determination threshold setting means for setting a determination threshold according to the fuel level detected by the fuel level sensor;
Determining means for determining that the fuel level sensor has failed when the fuel level detected by the fuel level sensor does not change by more than the determination threshold when the travel distance has changed by the determination distance or more. A fuel level sensor failure diagnosis device.   The determination threshold value setting means sets the determination threshold value to at least two predetermined values according to the detected fuel level, and the first predetermined value is applied in a region where the output characteristic of the fuel level sensor is substantially linear. 2. The fuel level sensor failure diagnosis apparatus according to claim 1, wherein the second predetermined value is applied in a region where an output characteristic of the fuel level sensor is nonlinear. 3.

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