JP2015021452A - Diagnosis device of fuel level sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a diagnostic device of a fuel level sensor capable of preventing misdiagnosis. SOLUTION: In a diagnostic device of a fuel level sensor for diagnosing an abnormality in a fuel level sensor when the output value of the fuel level sensor and the integrated value of the fuel consumption from an injector do not match, the inside of the fuel tank. If it is estimated that the fuel tank is refueled after the fuel is consumed within the range where the fuel level exceeds the point F, the integrated value of the fuel consumption is cleared. This avoids a situation in which only the integrated value of the fuel injection amount increases in a state where the output of the fuel level sensor does not change due to refueling, thereby preventing misdiagnosis. Further, when the integrated value of the fuel injection amount reaches a predetermined value in a state where the output of the fuel level sensor is stuck to the point F, it is diagnosed that the fuel level sensor has an abnormality. [Selection diagram] FIG. 5

Description

  The present invention relates to an apparatus for diagnosing a fuel level sensor provided in a fuel tank. In particular, the present invention relates to measures for preventing misdiagnosis.

  2. Description of the Related Art Conventionally, in a fuel tank mounted on a vehicle, a fuel level sensor for detecting a fuel level (fuel level) is provided in order to detect the remaining amount of fuel in the tank.

  Moreover, what is disclosed by patent document 1 and patent document 2 is known as a diagnostic apparatus for diagnosing the presence or absence of abnormality of this fuel level sensor. In view of the fact that the techniques disclosed in these patent documents have a correlation between the fuel injection amount from the injector and the fuel level decrease amount in the tank, the integrated value of the fuel injection amount and the output of the fuel level sensor (fuel level) If there is a deviation in the correlation with the output), the fuel level sensor is diagnosed as having an abnormality. For example, when the integrated value of the fuel injection amount has reached a predetermined amount, but the output of the fuel level sensor has not reached the amount of change corresponding thereto, it is diagnosed that an abnormality has occurred in the fuel level sensor. .

JP 2007-10574 A JP 2006-214390 A

  However, the conventional fuel level sensor diagnostic method may lead to a false diagnosis in the situation described below.

  In general, the output characteristics of the fuel level sensor have a stationary region in which the sensor output value hardly changes even if the fuel level changes within the range when the fuel level in the fuel tank exceeds a predetermined amount. Yes. For example, the range from the maximum fuel level in the fuel tank (so-called full tank) to the fuel level that is about 20 L lower in fuel amount is the immobile region. The lowest point of this immovable region (the range in which the sensor output value does not change) is generally called “point F”. That is, at the fuel level higher than the point F, even if the amount of fuel in the fuel tank changes, the output value of the fuel level sensor hardly changes.

  For this reason, for example, when the operation of the engine (consumption of fuel by fuel injection from the injector) and refueling into the fuel tank are repeated within a range where the fuel level exceeds the point F, The change in the fuel amount in the fuel tank does not appear in the output of the fuel level sensor.

  However, with the conventional fuel level sensor diagnostic method, even in such a situation, the integrated value of the fuel injection amount increases as the engine operates. That is, although the integrated value of the fuel injection amount is increased, a situation occurs in which no change appears in the output of the fuel level sensor due to the refueling. In such a situation, the fuel injection amount is integrated even though no abnormality has occurred in the fuel level sensor (when the fuel level drops below the F point, the corresponding output is made). Since there is a deviation in the correlation between the value and the output of the fuel level sensor, it is erroneously diagnosed that an abnormality has occurred in the fuel level sensor.

  FIG. 6 shows an example of temporal changes in the fuel level in the tank, the fuel injection amount integrated value, and the sensor output in this case. In the one shown in FIG. 6, refueling is performed at timing t1 in the drawing. That is, refueling is performed before the fuel level in the tank drops to the F point.

  As shown in FIG. 6, when the engine is operated from the state (timing t0) in which the fuel amount in the fuel tank is maximum (full tank), the fuel injection amount integrated value reaches A (timing). At t1), the tank fuel level lowering position corresponding to this fuel injection amount integrated value A has not reached point F, and the output of the fuel level sensor does not change.

  In this state, when the fuel tank is filled, the fuel tank is full, the engine is operated again, and the fuel injection amount integrated value is added by B (timing t2), the fuel injection amount integrated value is “A + B”. Become. Although this integrated value “A + B” is a value that lowers the fuel level in the tank below the F point (corresponding to a value exceeding the fuel injection amount integrated value f in the figure), it is actually in the fuel tank. Since the fuel level has only decreased to a level corresponding to the integrated value B from the state where the fuel tank is full, the output of the fuel level sensor does not change even in this case. That is, although the fuel injection amount integrated value is “A + B”, which is the value at which the output of the fuel level sensor should change, the actual fuel level decrease amount only decreases to a level corresponding to the integrated value B. Therefore, the output of the fuel level sensor does not change, and as a result, it is erroneously diagnosed that an abnormality has occurred even though the fuel level sensor is normal.

  As described above, in the conventional fuel level sensor diagnosis method, there is a possibility that the reliability of diagnosis cannot be obtained depending on the situation.

  The present invention has been made in view of this point, and an object of the present invention is to provide a fuel level sensor diagnostic device capable of preventing erroneous diagnosis.

-Solution principle of the invention-
The solution principle of the present invention taken to achieve the above object is to reset (clear) the integrated value of the fuel consumption in the non-moving region of the output of the fuel level sensor as the refueling is performed. Thus, it is possible to prevent misdiagnosis caused by the accumulation of fuel consumption.

-Solution-
Specifically, according to the present invention, when the output value of the fuel level sensor for detecting the liquid level of the fuel in the fuel tank does not match the fuel consumption integrated value, an abnormality has occurred in the fuel level sensor. A diagnosis device for a fuel level sensor to be diagnosed is assumed. With respect to the fuel level sensor diagnostic device, the fuel level in the fuel tank is within a range where the output value of the fuel level sensor does not change, and the fuel is consumed within this range. When it is estimated that the fuel has been supplied into the tank, the diagnosis that the abnormality has occurred in the fuel level sensor is not performed, or the diagnosis of the fuel level sensor is not performed.

  In the prior art, when the fuel level in the fuel tank is in a range where the output value of the fuel level sensor does not change, the fuel consumption increases with the fuel consumption regardless of the presence or absence of refueling. The amount integrated value was added. For this reason, when fueling is performed within the above range, there is a possibility that the output value of the fuel level sensor and the integrated value of fuel consumption do not match even though the fuel level sensor is normal. . As a result, there is a case where the fuel level sensor is erroneously diagnosed as having an abnormality.

  In the present solution, the fuel level in the fuel tank is in a range where the output value of the fuel level sensor does not change, and the fuel is supplied to the fuel tank while the fuel is consumed within this range. When it is estimated that the fuel level sensor has been performed, the diagnosis that the fuel level sensor is abnormal is not performed, or the diagnosis of the fuel level sensor is not performed. For this reason, it is possible to prevent a misdiagnosis caused by refueling in the fuel tank in a situation where the change in the fuel level in the fuel tank does not appear in the output value of the fuel level sensor. , The reliability of diagnosis can be improved.

  Specifically, the fuel level in the fuel tank is within a range where the output value of the fuel level sensor does not change, and the fuel is consumed within this range. When it is estimated that refueling has been performed, the fuel consumption integrated value is reset, thereby eliminating the state where the output value of the fuel level sensor does not match the fuel consumption integrated value, The diagnosis that an abnormality has occurred in the fuel level sensor is not performed.

  That is, by resetting the fuel consumption integrated value, the situation in which the fuel consumption integrated value increases despite the fact that the output of the fuel level sensor hardly changes is solved. As a result, although the fuel level sensor is normal, the fuel level sensor output value and the fuel consumption integrated value are not matched due to the fact that refueling has been performed, resulting in erroneous diagnosis. Can be prevented.

  An example of the range in which the output value of the fuel level sensor does not change is that the fuel level in the fuel tank is within a predetermined level or more.

  In this case, it is presumed that the fuel tank is refueled when the output value of the fuel level sensor does not change with a value corresponding to the range in which the output value of the fuel level sensor does not change. If the fuel consumption integrated value reaches a predetermined value, it is diagnosed that an abnormality has occurred in the fuel level sensor.

  This is because when the fuel consumption integrated value becomes a relatively large value that deviates from the range where the output value of the fuel level sensor does not change, the output value of the fuel level sensor still does not change with a value corresponding to the range. Since it can be determined that the fuel level sensor is stuck (fixed) within this range, in this case, it is diagnosed that an abnormality has occurred in the fuel level sensor. That is, when it is determined that an abnormality has occurred in the fuel level sensor, the reliability of the diagnostic apparatus can be ensured by performing the abnormality determination.

  Further, when the output value of the fuel level sensor does not change with a value corresponding to a range other than the range where the output value of the fuel level sensor does not change, and the fuel consumption integrated value reaches a predetermined value Makes a diagnosis that an abnormality has occurred in the fuel level sensor.

  This is a diagnostic operation when the fuel level sensor is stuck (fixed) in a range other than the above range. In this case, the fuel consumption integrated value regardless of whether or not fuel is supplied to the fuel tank. When the value reaches the predetermined value, it is diagnosed that an abnormality has occurred in the fuel level sensor. In other words, if the fuel level sensor is stuck in a range other than the above range, the above-described misdiagnosis caused by the fuel supply into the fuel tank will not be caused. When the value reaches the predetermined value, it is diagnosed that an abnormality has occurred in the fuel level sensor.

  The range in which the output value of the fuel level sensor does not change may be that the fuel level in the fuel tank is within a predetermined level or less.

  In this case, it is possible to prevent the remaining amount of fuel from being determined to be “0” even though the fuel still remains in the fuel tank due to the refueling within the above range.

  In the present invention, the fuel level in the fuel tank is in a range where the output value of the fuel level sensor does not change, and the fuel is supplied into the fuel tank while the fuel is consumed within this range. If it is estimated that the fuel level sensor is abnormal, the diagnosis that the fuel level sensor is abnormal is not performed, or the diagnosis of the fuel level sensor is not performed. Accordingly, it is possible to prevent a misdiagnosis due to the fact that the fuel is supplied into the fuel tank in a situation where the change in the liquid level of the fuel in the fuel tank does not appear in the output value of the fuel level sensor. .

It is a figure which shows schematic structure of the engine and intake / exhaust system which concern on embodiment. It is a block diagram which shows the control system of an engine. It is a flowchart figure which shows the first half of the diagnostic process of a fuel level sensor. It is a flowchart figure which shows the second half of the diagnostic process of a fuel level sensor. It is a figure which shows an example of the time change of each of the fuel level in a tank, fuel injection amount integrated value, and sensor output in embodiment. It is a figure which shows an example of the time change of each of the fuel level in a tank in the prior art, fuel injection amount integrated value, and a sensor output.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present embodiment, a case where the present invention is applied to a multi-cylinder (for example, four-cylinder) gasoline engine (internal combustion engine) will be described.

-Engine-
FIG. 1 is a diagram showing a schematic configuration of an engine 1 and its intake / exhaust system according to the present embodiment. In FIG. 1, only the configuration of one cylinder of the engine 1 is shown.

  The engine 1 according to the present embodiment includes a cylinder block 12 in which four cylinders 11 are formed, and a cylinder head 13 attached to the top of the cylinder block 12. A piston 14 is inserted into each cylinder 11 so as to be capable of reciprocating. Each piston 14 is connected to a crankshaft 16 via a connecting rod 15.

  An air cleaner 21, an air flow meter 93, an intake air temperature sensor 94, and a throttle valve 22 are provided in the intake passage 2 of the engine 1. The throttle valve 22 is driven by a throttle motor 23. The intake passage 2 includes an intake manifold 24 that distributes intake air to each cylinder 11, and an intake port 25 that is provided for each cylinder 11 and connected to the intake manifold 24.

On the other hand, an O ₂ sensor 96 and a catalytic converter 31 are provided in the exhaust passage 3. The exhaust passage 3 includes an exhaust port 32 provided for each cylinder 11 and an exhaust manifold 33 that collects the exhaust ports 32.

  The cylinder head 13 is provided with an intake valve 26 for opening and closing the intake port 25 and an exhaust valve 36 for opening and closing the exhaust port 32. These valves 26 and 36 are driven to open and close in synchronism with the crankshaft 16 by a valve mechanism 17 including a cam or the like.

  Each cylinder 11 is provided with an injector (fuel injection valve) 4 and a spark plug 5.

  The fuel supply system for supplying fuel to the injector 4 is provided with a fuel tank T, a fuel supply pipe 41 and a fuel pump P. In this fuel supply system, the fuel pump P pumps up the fuel in the fuel tank T and pumps the fuel toward the injector 4 through the fuel supply pipe 41. As the fuel pump P, an electric fuel pump using an electric motor is used. The fuel pump P may be either an out-tank type disposed outside the fuel tank T or an in-tank type disposed inside the fuel tank T.

  A fuel level sensor 99 is provided inside the fuel tank T. The fuel level sensor 99 is for detecting the remaining amount of fuel in the fuel tank T, and for example, an electric type is used. In the electric fuel level sensor 99, a float 99a disposed in the fuel tank T is connected via a lever 99b. Then, the lever 99b moves as the float 99a moves up and down due to fluctuations in the fuel level (fuel level height) in the fuel tank T, and the moving position of the lever 99b is converted into a resistance value of a variable resistor. An output signal corresponding to the resistance value is output to the engine ECU 8. Thus, the fuel level in the fuel tank T can be detected based on this output signal. The configuration of the fuel level sensor 99 is not limited to this.

  Further, the fuel tank T is provided with a fuel cap sensor 9C for detecting opening and closing of the fuel cap 42 provided at the fuel filler port. As this fuel cap sensor 9C, various sensors such as a switch type, an optical type and a capacitance type can be applied.

  In the engine 1 configured as described above, when fuel is injected from the injector 4 into the cylinder 11 in the intake stroke, an air-fuel mixture is formed in the cylinder 11, and after the compression stroke, the air-fuel mixture is ignited. It is ignited by the spark of the plug 5 and burns. The piston 14 reciprocates due to the combustion pressure generated by the combustion, and this reciprocating motion is transmitted to the crankshaft 16 via the connecting rod 15 and taken out as the output of the engine 1.

  Further, the exhaust gas after combustion is guided to the exhaust passage 3 and purified by the catalytic converter 31, and then released to the atmosphere through a muffler (not shown).

-Description of control block-
The operating state of the engine 1 configured as described above is controlled by the engine ECU 8. As shown in FIG. 2, the engine ECU 8 includes a CPU (Central Processing Unit) 81, a ROM (Read Only Memory) 82, a RAM (Random Access Memory) 83, a backup RAM 84, and the like.

The CPU 81, ROM 82, RAM 83, and backup RAM 84 are connected to each other via a bus 87, and are connected to an external input circuit 85 and an external output circuit 86. The external input circuit 85 includes a crank position sensor 91, a water temperature sensor 92, the air flow meter 93, an intake air temperature sensor 94, a throttle opening sensor 95, an O ₂ sensor 96, an accelerator opening sensor 97, a cam angle sensor 98, and the fuel. A level sensor 99, a shift position sensor 9A for detecting an operation position of a shift lever 71 provided in the shift operation device 7, an IG (ignition) switch 9B, the fuel cap sensor 9C, and the like are connected. Since the configuration and function of each sensor and switch are well known, a description thereof is omitted here.

  On the other hand, the external output circuit 86 is connected to the throttle motor 23 that drives the throttle valve 22, the injector 4, the igniter 51, and the like.

  The engine ECU 8 executes various controls of the engine 1 based on detection signals from the various sensors. For example, known ignition timing control of the spark plug 5, drive control of the throttle motor 23, and the like are executed.

Further, the engine ECU 8 executes air-fuel ratio control (correction control of the fuel injection amount from the injector 4 based on the output of the O ₂ sensor 96). That is, the engine ECU 8 corrects the fuel injection amount of the injector 4 so that the air-fuel ratio of the air-fuel mixture introduced to each cylinder 11 is maintained at the target air-fuel ratio (for example, the theoretical air-fuel ratio). Specifically, the engine ECU 8 calculates a basic fuel injection amount that is a basis of the fuel injection amount to be injected into the cylinder 11 based on the output signals of the crank position sensor 91 and the air flow meter 93, and the basic fuel injection amount. On the other hand, the final fuel injection amount is determined by performing air-fuel ratio feedback control using a known air-fuel ratio feedback correction coefficient or air-fuel ratio learning control using an air-fuel ratio learning value. Then, the engine ECU 8 outputs a control signal for the fuel injection period corresponding to the fuel injection pressure to the injector 4 so that this final fuel injection amount is obtained.

  Further, the engine ECU 8 stores the integrated value of the fuel injection amount from the injector 4 in the RAM 83. Specifically, the fuel injection amount calculated based on the fuel injection pressure and the fuel injection period is integrated. The fuel injection amount integration start timing and the usage form of the fuel injection amount integration value will be described later.

-Characteristics and issues of fuel level sensor-
The output characteristic of the fuel level sensor 99 has a non-moving region in which the sensor output value hardly changes even if the fuel level changes within the range when the fuel level in the fuel tank T exceeds a predetermined amount. ing. In the range where the fuel level in the fuel tank T exceeds a predetermined amount, the float 99a of the fuel level sensor 99 comes into contact with the upper surface (ceiling surface) in the fuel tank T, and the float 99a cannot float further. Because. That is, in this immovable region, even if the fuel level changes, the float 99a remains in contact with the upper surface in the fuel tank T, and the sensor output value hardly changes. For example, the range from the maximum fuel level in the fuel tank T (so-called full tank) to the fuel level about 20 L lower in fuel amount is the immobile region. The amount of fuel that becomes the immovable region is not limited to the above value, and varies depending on the size and shape of the fuel tank T.

  As described above, the lowest point of the immovable region (the range in which the sensor output value does not change) is generally called “F point”. That is, at the fuel level higher than the point F, even if the amount of fuel in the fuel tank T changes, the output value of the fuel level sensor 99 hardly changes.

  Therefore, for example, within the range where the fuel level exceeds the point F (the range in which the output value of the fuel level sensor in the present invention does not change), the operation of the engine 1 (consumption of fuel by fuel injection from the injector 4) and In the case where the refueling into the fuel tank T is repeated, the change in the fuel amount in the fuel tank T does not appear in the output of the fuel level sensor 99.

  In the fuel level sensor diagnosis method in the prior art, when the correlation between the integrated value of the fuel injection amount and the output of the fuel level sensor (output corresponding to the fuel level) is shifted, an abnormality occurs in the fuel level sensor. I was diagnosed. Therefore, as described above, when the engine operation and the fuel supply into the fuel tank are repeated within the range where the fuel level exceeds the F point, the change in the fuel amount in the fuel tank is caused by the change in the fuel level sensor. Although the output does not appear, the integrated value of the fuel injection amount increases with the operation of the engine. That is, although the integrated value of the fuel injection amount is increased, a situation occurs in which no change appears in the output of the fuel level sensor due to the refueling. In such a situation, the fuel injection amount is integrated even though no abnormality has occurred in the fuel level sensor (when the fuel level drops below the F point, the corresponding output is made). Since there is a deviation in the correlation between the value and the output of the fuel level sensor, it is erroneously diagnosed that an abnormality has occurred in the fuel level sensor.

-Fuel level sensor diagnostic process-
A feature of the present embodiment is that a diagnosis process of the fuel level sensor 99 that does not cause the erroneous diagnosis is performed. First, the outline of the diagnosis process of the fuel level sensor 99 will be described.

  The stationary region where the sensor output value hardly changes even when the fuel level changes includes a range where the fuel level in the fuel tank T exceeds a predetermined amount (a range exceeding the F point) and a fuel as described later. There is a range in which the fuel level in the tank T falls below a predetermined amount (the uppermost point of this range is generally called “point E”), but here the fuel level in the fuel tank T exceeds the point F. The diagnosis processing in the case of being in the range will be described as an example.

  In the diagnosis process of the fuel level sensor 99 in the present embodiment, it is estimated that the fuel level is in the range exceeding the point F, and the fuel is supplied into the fuel tank T in a state where the fuel is consumed within this range. In this case, the diagnosis that an abnormality has occurred in the fuel level sensor 99 is not performed. Specifically, the integrated value of the fuel injection amount (fuel consumption integrated value) used for the diagnosis process of the fuel level sensor 99 is cleared, that is, the integrated value of the fuel injection amount is reset to “0”. Therefore, the diagnosis that an abnormality has occurred is not performed. This avoids a situation in which only the integrated value of the fuel injection amount increases in a state where there is no change in the output of the fuel level sensor 99 due to the fact that refueling has been performed. Try to prevent.

  When the fuel level falls below the point F, normal diagnosis processing is performed. That is, a diagnosis process is performed based on whether or not the output value of the fuel level sensor 99 is consistent with the fuel consumption integrated value.

  Next, the diagnosis process of the fuel level sensor 99 will be specifically described.

  3 and 4 are flowcharts showing the procedure of the diagnostic process of the fuel level sensor 99. FIG. The diagnosis process shown in this flowchart is repeatedly executed by the engine ECU 8 with a predetermined period.

  First, in step ST1, is the current value of the output from the fuel level sensor 99 (the value of the output signal representing the current fuel level) smaller than the minimum output value (stored minimum value) stored in the RAM 83? Determine whether or not. That is, the output value from the fuel level sensor 99 is monitored for each routine of this flowchart, and the stored value (stored every time the output value becomes smaller (every smaller than the stored minimum output value)). When updating (minimum value), it is determined whether or not the current output value from the fuel level sensor 99 is smaller than the minimum output value stored in the RAM 83.

  If the current output value from the fuel level sensor 99 is smaller than the stored output minimum value and YES is determined in step ST1, the process proceeds to step ST2, and this current value (EFLSRM) is converted to the output minimum value (EFLSRMN). ), The process proceeds to step ST3.

  On the other hand, if the current value of the output from the fuel level sensor 99 is equal to or greater than the stored minimum output value and a NO determination is made in step ST1, the minimum output value (EFLSRMN) is not updated and the process returns to step ST3. Move.

  In step ST3, it is determined whether or not the current value of the output from the fuel level sensor 99 is larger than the maximum output value (stored maximum value) stored in the RAM 83. That is, the output value from the fuel level sensor 99 is monitored for each routine of this flowchart, and each time this output value increases (every time the stored output maximum value becomes larger), the stored value (stored) When the maximum value is updated, it is determined whether or not the current output value from the fuel level sensor 99 is greater than the maximum output value stored in the RAM 83.

  If the current output value from the fuel level sensor 99 is larger than the stored maximum output value and YES is determined in step ST3, the process proceeds to step ST4, where the current value (EFLSRRM) is converted to the maximum output value (EFLSRMX). ), The process proceeds to step ST5.

  On the other hand, if the current value of the output from the fuel level sensor 99 is equal to or less than the stored maximum output value and a NO determination is made in step ST3, the output maximum value (EFLSRMX) is not updated and the process returns to step ST5. Move.

  In the operations of these steps ST1 to ST4, the situation in which the fluctuation of the liquid level in the fuel tank T caused by the vibration of the vehicle body or the fuel consumption during the traveling of the vehicle is reflected in the output of the fuel level sensor 99. In this case, the minimum output value (EFLSRMN) and the maximum output value (EFLSRMX) are updated, and the difference between the minimum output value (EFLSRMN) and the maximum output value (EFLSRMX) increases. To go. That is, when the output of the fuel level sensor 99 changes normally according to the fluctuation of the liquid level in the fuel tank T, this divergence increases.

  In step ST5, a value obtained by subtracting the minimum output value (EFLSRMN) from the maximum output value (EFLSRMX), that is, whether or not the difference between the maximum output value (EFLSRMX) and the minimum output value (EFLSRMN) is less than a predetermined amount α. Determine. That is, it is determined whether or not the change in the output value from the fuel level sensor 99 is the same as the change in the output value when there is almost no fluctuation in the liquid level in the fuel tank T. Specific examples of the predetermined amount α include a value corresponding to 30 mm in fuel level. This value is not limited to this, and is set as appropriate, but is set to a value smaller than the fluctuation range of the liquid level in the fuel tank T due to the influence of vehicle body vibration in the normal vehicle running state. .

  When the value obtained by subtracting the minimum output value (EFLSRMN) from the maximum output value (EFLSRMX) is equal to or greater than the predetermined amount α, and when NO is determined in step ST5, the process proceeds to step ST6 and the fuel tank caused by the vehicle body vibration or the like. Since the fluctuation of the liquid level in T is reflected in the output of the fuel level sensor 99, it is determined that the fuel level sensor 99 is normal. In addition, a fuel consumption integrated value (EVISTKSUM; fuel consumption integrated value), an output maximum value (EFLSRMX), and a minimum output value (EFLSRMN), which will be described later, are initialized and returned.

  On the other hand, if the value obtained by subtracting the minimum output value (EFLSRMN) from the maximum output value (EFLSRMX) is less than the predetermined amount α, and if YES is determined in step ST5, the process proceeds to step ST7 to integrate the fuel consumption in the stack. I do. That is, when the value obtained by subtracting the minimum output value (EFLSRMN) from the maximum output value (EFLSRMX) is less than the predetermined amount α, the float 99a of the fuel level sensor 99 is stuck at any position within the movable range. Assuming that there is a possibility of being stuck (fixed), a temporary determination is made that the fuel cell is in a stack, and the fuel consumption (fuel injection amount from the injector 4) in the stack is integrated. This accumulation of the fuel consumption in the stack is performed until an accumulated value clearing process described later is performed (until the clearing process is performed in step ST13 or when the fuel level sensor 99 is determined to be abnormal in step ST15). Until the clear process is performed).

  In a state where the fuel consumption in the stack is integrated, in step ST8 (FIG. 4), the output value of the fuel level sensor 99 is a value when the fuel level is within the range exceeding the F point. It is determined whether or not. That is, it is determined whether or not the output of the fuel level sensor 99 is stuck to the point F.

  If the output of the fuel level sensor 99 is stuck to the point F, YES is determined in step ST8 and the process proceeds to step ST9. In this step ST9, the amount of fuel consumption with F sticking is integrated. That is, the fuel consumption amount (the fuel injection amount from the injector 4) during the period in which the output of the fuel level sensor 99 is stuck to the point F is integrated.

  On the other hand, if the output of the fuel level sensor 99 is not stuck to the point F, NO is determined in step ST8 and the process proceeds to step ST10. In this step ST10, the integrated value of the fuel consumption amount with the F-point sticking is cleared. In other words, the determination that the stack is in progress is not based on the F-point stuck stack, but is based on the stack in the other range, and the integrated value of the fuel consumption during the F-point stuck is cleared (reset).

  In this way, after clearing the integrated value of the fuel consumption during sticking F, the process proceeds to step ST14, where it is determined whether or not the integrated fuel consumption value in the stack exceeds a predetermined amount γ. That is, although the integrated value of the fuel injection amount of the injector 4 after the determination that it is in the stack exceeds the predetermined amount γ, the minimum output value (EFLSRMN) and the maximum output value are still present. It is determined whether or not the deviation from (EFLSRMX) is less than the predetermined amount α and it is determined that the stack is being stacked.

  Immediately after it is determined that the fuel cell is in the stack, the fuel consumption integrated value in the stack is still small and does not exceed the predetermined amount γ. Therefore, NO is determined in step ST14 and the process returns. That is, the process returns without determining that the fuel level sensor 99 is abnormal.

  On the other hand, when the output of the fuel level sensor 99 is not in a state of sticking to the point F (when NO is determined in step ST8), it is determined that the stack is being stacked (step ST8). If the elapsed time after the YES determination in ST5 becomes relatively long and the accumulated fuel consumption value in the stack exceeds the predetermined amount γ, a YES determination is made in step ST14, and the process proceeds to step ST15. In this step ST15, it is determined that an abnormality has occurred in the fuel level sensor 99. That is, although the integrated value of the injection amount from the injector 4 exceeds the predetermined amount γ (YES is determined in step ST14), the minimum output value (EFLSRMN) and the maximum output value (EFLSRMX) still remain. If the deviation is less than the predetermined amount α (YES is determined in step ST5), the fuel level sensor 99 has a stack (a range other than the F point, for example, a stack at the center position in the fuel tank T). As a result, it is determined that an abnormality has occurred in the fuel level sensor 99.

  In this way, when it is determined that an abnormality has occurred in the fuel level sensor 99, the MIL (warning light) on the meter panel in the passenger compartment is lit to urge the driver to warn and the engine ECU 8 is provided. Abnormal information is written in the diagnosis.

  On the other hand, if the determination in step ST8 is YES, and in step ST9, the integration of the fuel consumption with F point sticking is performed, the integration value of the fuel consumption in F sticking is less than the predetermined amount β in step ST11. It is determined whether or not. This predetermined amount β is a value corresponding to the integrated injection amount when the fuel level is lowered from the full tank state in the fuel tank T to the F point, and is set to a value smaller than the γ by a predetermined amount. ing. That is, in this step ST11, it is determined whether or not the integrated value of the injection amount from the injector 4 has yet reached the value for reducing the fuel level to the F point.

  If the fuel consumption integrated value with F point sticking is equal to or greater than the predetermined amount β and NO is determined in step ST11, the process proceeds to step ST14, and as described above, the fuel consumption integrated value in the stack is the predetermined amount γ. It shifts to determination of the presence or absence of abnormality of the fuel level sensor 99 by determining whether it is over. That is, in the situation where the output from the fuel level sensor 99 hardly changes even though the fuel consumption integrated value with the F point sticking is a value that lowers the fuel level to the F point or less. Depending on whether or not the intermediate fuel consumption integrated value exceeds the predetermined amount γ, the process proceeds to the determination of whether or not the fuel level sensor 99 is abnormal.

  On the other hand, if the fuel consumption integrated value with point F is less than the predetermined amount β and the determination in step ST11 is YES, the process proceeds to step ST12 to determine whether or not refueling into the fuel tank T has been performed. To do. That is, it is determined whether or not the fuel tank T has been refueled before the fuel level drops to the F point.

  This fueling determination is a determination of whether or not it is estimated that fueling has been performed (whether or not there is a possibility of fueling), and the shift lever detected by the shift position sensor 9A. Whether the position of 71 is N (neutral position) or P (parking position) continues for a predetermined time or more, whether the IG switch 9B is turned off, whether the fuel cap 42 is closed by the fuel cap sensor 9C. This is performed depending on whether or not opening / closing is detected. For example, when the state where the position of the shift lever 71 is N or P continues for 60 seconds or more, when the IG switch 9B is turned off, or when the opening / closing of the fuel cap 42 is detected, the situation occurs. It is determined (estimated) that the fuel tank T has been refueled. You may make it determine the presence or absence of oil supply combining several among these oil supply determination.

  If refueling into the fuel tank T is not performed (it is estimated that refueling is not performed), and if NO is determined in step ST12, the process proceeds to step ST14, and as described above, the fuel consumption in the stack The process proceeds to determination of whether or not the fuel level sensor 99 is abnormal by determining whether or not the integrated value exceeds the predetermined amount γ.

  On the other hand, if fuel is being supplied into the fuel tank T (it is estimated that fuel has been supplied), and if YES is determined in step ST12, the process proceeds to step ST13, where the accumulated fuel consumption value in the stack is cleared. (Reset. That is, when the fuel level is in the range exceeding the F point and the fuel in the fuel tank T is consumed while the fuel is consumed within this range (when it is estimated that the fuel has been supplied). ) Clear the accumulated fuel consumption value in the stack.

  As a result of clearing the fuel consumption integrated value in the stack in this way, in step ST14, the fuel consumption integrated value in the stack does not exceed the predetermined amount γ (in the present invention, “reset fuel consumption integrated value”). In this step ST14, NO is determined and the process is returned. This corresponds to “the state in which the output value of the fuel level sensor and the fuel consumption integrated value do not match” is eliminated. That is, the process returns without determining that the fuel level sensor 99 is abnormal. Thereby, the diagnosis that an abnormality has occurred in the fuel level sensor 99 is not performed. As a result, in a state where there is no change in the output of the fuel level sensor 99 due to refueling, the situation where only the integrated value of the fuel injection amount increases is avoided, thereby preventing misdiagnosis. It becomes possible.

  FIG. 5 shows an example of temporal changes in the tank fuel level, the fuel injection amount integrated value, and the sensor output in this embodiment. In the one shown in FIG. 5, refueling is performed at timing T1 in the drawing. That is, refueling is performed before the fuel level in the tank drops to the F point.

  As shown in FIG. 5, when the engine 1 is operated from the state (timing T0) in which the fuel amount in the fuel tank T is maximum (full tank), the fuel injection amount integrated value reaches A. At (timing T1), the tank fuel level lowering position corresponding to this fuel injection amount integrated value A has not reached point F, and the output of the fuel level sensor 99 does not change. In this embodiment, refueling is performed at this point (the state in which YES is determined in step ST11 and YES in step ST12 in the flowchart), and accordingly, the fuel consumption integrated value (in the stack) The fuel consumption integrated value) is cleared (operation of step ST13 in the flowchart).

  With this refueling, the fuel tank T becomes full, the engine 1 is operated again, and the fuel injection amount integrated value increases. Since the fuel consumption integrated value is cleared, the fuel injection amount integrated value is f (fuel injection amount integrated value at which the change of the output value starts when the fuel level sensor 99 is normal) in the figure. Until the fuel level in the tank reaches the point F, the fuel injection amount integrated value reaches f in the figure when the fuel level in the tank reaches the point F and the output value of the fuel level sensor 99 changes. Will do. In FIG. 5, the fuel level in the tank reaches the point F at timing T2, and the change in the output value of the fuel level sensor 99 is started (in the case shown in FIG. 5, the fuel level in the tank decreases). The output value of the fuel level sensor 99 is assumed to increase, but conversely, the output value may decrease). In this way, the output value of the fuel level sensor 99 and the fuel injection amount integrated value are matched, and it is diagnosed that there is no abnormality in the fuel level sensor 99. In other words, in a state where there is no change in the output of the fuel level sensor 99 due to refueling, a situation in which only the integrated value of the fuel injection amount increases is avoided, thereby preventing misdiagnosis. Is possible.

(Modification)
In the above-described embodiment, the diagnosis process when the fuel level in the fuel tank T is in the range exceeding the F point has been described.

  The present invention is not limited to this, and in a range where the fuel level in the fuel tank T is less than a predetermined amount, even in a stationary region where the sensor output value hardly changes even if the fuel level changes within that range. Applicable. As described above, the uppermost point of this immovable region (the range where the sensor output value does not change) is generally called “E point”.

  Specifically, in a range where the fuel level in the fuel tank T is lower than the point E, the float 99a of the fuel level sensor 99 has reached the lowest position in the movable range, and even if the fuel level falls, the float 99a cannot move any further (move downward). In other words, in this immovable region, even if the fuel level changes, the float 99a remains at the lowest position in the movable range, and the sensor output value hardly changes. For example, the range from the level of the remaining amount of fuel “0” in which no fuel exists in the fuel tank T to the fuel level that is about 10 L higher in fuel amount is the immobile region. The amount of fuel that becomes the immovable region is not limited to the above value, and varies depending on the size and shape of the fuel tank T.

  Thus, at the fuel level lower than the point E, even if the amount of fuel in the fuel tank T changes, the output value of the fuel level sensor 99 hardly changes.

  For this reason, for example, the operation of the engine 1 (consumption of fuel by fuel injection from the injector 4) and fuel supply into the fuel tank T (small amount of fuel supply) are repeated within a range where the fuel level is lower than the point E. In that case, the change in the fuel amount in the fuel tank T does not appear in the output of the fuel level sensor 99.

  Even in such a situation, as in the case of the above-described embodiment, the fuel level is in the range below the point E, and the fuel is supplied into the fuel tank T with the fuel being consumed within this range. In the case (when it is estimated that refueling has been performed), the integrated value of the fuel injection amount is reset to “0”. Specifically, the integrated value of the fuel injection amount used for the diagnosis process of the fuel level sensor 99 (the integrated value of the fuel injection amount from the time when the fuel level has decreased to point E) is cleared, that is, this fuel injection amount. Is reset to “0”. According to this, when the integrated value of the fuel injection amount is integrated without being reset, it is possible to prevent erroneous diagnosis that the remaining amount of fuel becomes “0”. In other words, the remaining amount of fuel has become “0” because the fuel has been supplied, but the fuel is still in the fuel tank T (the fuel remains in the range below the point E). It can prevent judging.

-Other embodiments-
In the embodiments and modifications described above, the case where the present invention is applied to an in-line four-cylinder gasoline engine has been described. In the present invention, the number of cylinders and the type of engine (V type, horizontally opposed type, etc.) are not particularly limited. The present invention can also be applied to a diesel engine. The present invention can also be applied to an engine that uses ethanol alone or a multi-fuel engine that can use a mixed fuel of ethanol and gasoline.

  In the embodiment and the modification, the fuel consumption integrated value is the integrated value of the fuel injection amount from the injector 4. The present invention is not limited to this, and when an evaporative fuel processing device for supplying evaporative fuel generated in the fuel tank T to the intake passage 2 is mounted, the amount of fuel supplied to the intake passage 2 by the evaporative fuel processing device is reduced. The integrated value may be added to the integrated value of the fuel injection amount from the injector 4, and this value may be handled as the integrated fuel consumption value.

  Further, in the embodiment and the modified example, when fuel is supplied into the fuel tank T in a state where the fuel level is in the immovable region (when it is estimated that fuel is supplied), the fuel consumption integrated value Is reset so that the diagnosis that an abnormality has occurred in the fuel level sensor 99 is not performed. The present invention is not limited to this, and when fuel is supplied into the fuel tank T in a state where the fuel level is in the immovable region (when it is estimated that fuel has been supplied), the fuel level sensor 99 The diagnosis may not be executed. For example, in the flowchart of FIG. 4, if YES is determined in step ST <b> 12 (when it is determined that there is refueling), the diagnosis of the fuel level sensor 99 is not executed by returning as it is.

  In the embodiment and the modification, the case where the present invention is applied to a conventional vehicle (a vehicle equipped with only the engine 1 as a driving force source) has been described. However, a hybrid vehicle (an engine and an electric motor are mounted as a driving force source) The present invention can also be applied to a vehicle.

  The present invention can be applied to a fuel level sensor diagnostic device that detects a fuel level in a fuel tank mounted on a vehicle.

1 engine (internal combustion engine)
4 Injector 42 Fuel cap 8 Engine ECU
99 Fuel level sensor 9A Shift position sensor 9B IG switch 9C Fuel cap sensor T Fuel tank

Claims (6)

A fuel level sensor diagnostic device that diagnoses that an abnormality has occurred in the fuel level sensor when the output value of the fuel level sensor that detects the liquid level of the fuel in the fuel tank does not match the fuel consumption integrated value In
The fuel level in the fuel tank is in a range where the output value of the fuel level sensor does not change, and it is estimated that fuel has been supplied into the fuel tank while the fuel is consumed within this range. In such a case, the fuel level sensor diagnosis apparatus is configured not to diagnose that the fuel level sensor is abnormal or not to perform diagnosis of the fuel level sensor. The fuel level sensor diagnostic apparatus according to claim 1, wherein:
The fuel level in the fuel tank is in a range where the output value of the fuel level sensor does not change, and it is estimated that fuel has been supplied into the fuel tank while the fuel is consumed within this range. If this is the case, the fuel consumption integrated value is reset, thereby eliminating the state where the output value of the fuel level sensor and the fuel consumption integrated value do not match, thereby causing an abnormality in the fuel level sensor. An apparatus for diagnosing fuel level sensor, characterized in that the diagnosis is not performed. The fuel level sensor diagnostic device according to claim 1 or 2,
The range in which the output value of the fuel level sensor does not change is a range in which the fuel level in the fuel tank is equal to or higher than a predetermined level. The fuel level sensor diagnostic device according to claim 3, wherein
The fuel level sensor output value does not change with a value corresponding to a range in which the fuel level sensor output value does not change, and it is not estimated that the fuel tank has been refueled. An apparatus for diagnosing a fuel level sensor configured to diagnose that an abnormality has occurred in the fuel level sensor when the integrated quantity value reaches a predetermined value. The fuel level sensor diagnostic device according to claim 3 or 4,
When the output value of the fuel level sensor does not change with a value corresponding to a range other than the range where the output value of the fuel level sensor does not change, and the fuel consumption integrated value reaches a predetermined value, A fuel level sensor diagnostic device, wherein the fuel level sensor is configured to diagnose that an abnormality has occurred in the fuel level sensor. The fuel level sensor diagnostic device according to claim 1 or 2,
The range in which the output value of the fuel level sensor does not change is a range in which the fuel level in the fuel tank is not more than a predetermined level.

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