JP2010071081A - Device for diagnosing abnormality of fuel level detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately execute abnormality diagnosis of a fuel level detector irrespective of alcohol concentration of fuel. <P>SOLUTION: An alcohol concentration sensor 37 detecting alcohol concentration of the fuel is mounted on a fuel tank 30, a fuel pipe 32 or a delivery pipe 33, and abnormality diagnosis of the fuel level detector 39 is executed based on a relation between output change quantity of the fuel level detector 39 and fuel consumption quantity estimated from suction air quantity integration value during abnormality diagnosis period. In the execution, diagnosis conditions (threshold or diagnosis index) are changed or corrected based the alcohol concentration of fuel detected by the alcohol concentration sensor 37. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an abnormality diagnosis device for a fuel level detector that performs abnormality diagnosis of a fuel level detector that detects a fuel level (remaining amount of fuel) in a fuel tank.

As a conventional abnormality diagnosis device for a fuel level detector, for example, as described in Patent Documents 1 to 3 below, based on the relationship between the fuel consumption for a predetermined period and the output change amount of the fuel level detector. There is a fuel level detector that performs abnormality diagnosis.
Japanese Patent Laid-Open No. 10-73468 Japanese Patent Laid-Open No. 10-184479 JP 2007-10574 A

  In all of the above Patent Documents 1 to 3, the fuel consumption amount is obtained by integrating the fuel injection amount from the fuel injection valve. However, in recent years, the intake air amount is integrated and the fuel consumption is calculated from the integrated value. A technique has been proposed in which the amount of fuel is estimated and abnormality of the fuel level detector is diagnosed based on the relationship between the estimated fuel consumption and the output change amount of the fuel level detector.

In recent years, demands for automobiles equipped with engines (internal combustion engines) that can use gasoline, alcohol, and mixed fuels of both as fuels have increased due to social demands such as reducing CO ₂ emissions and using alternative fuels for oil. is doing. In such an automobile, when fuel with a different alcohol concentration from the previous time is supplied to the fuel tank, the alcohol concentration of the fuel in the fuel tank changes. Since the stoichiometric air-fuel ratio differs between gasoline and alcohol, if the alcohol concentration of the fuel changes, the stoichiometric air-fuel ratio of the fuel also changes, so that the fuel injection amount (air-fuel ratio) is controlled according to the alcohol concentration of the fuel. It has become.

  Accordingly, the relationship between the integrated value of the intake air amount and the fuel consumption changes corresponding to the change in the air-fuel ratio according to the alcohol concentration of the fuel. The fuel consumption is estimated without considering the change in the fuel consumption, so when the alcohol-mixed fuel is supplied into the fuel tank, the estimation accuracy of the fuel consumption is based on the change in the air-fuel ratio due to the alcohol concentration of the fuel. As a result, there is a possibility of misdiagnosing the presence or absence of abnormality of the fuel level detector.

  The present invention has been made in consideration of such circumstances, and therefore the object of the present invention is to accurately perform abnormality diagnosis of the fuel level detector regardless of the alcohol concentration of the fuel. An object of the present invention is to provide an abnormality diagnosis device for a fuel level detector.

  In order to achieve the above object, the invention according to claim 1 is directed to a fuel level detector for detecting the fuel level in the fuel tank, and a fuel consumption for integrating the intake air amount and estimating the fuel consumption amount from the integrated value. An amount diagnosing unit; and an abnormality diagnosing unit for diagnosing an abnormality of the fuel level detector based on a relationship between the fuel consumption estimated by the fuel consumption amount estimating unit and an output change amount of the fuel level detector. In the abnormality diagnosis device of the fuel level detector, the alcohol concentration determination means for detecting or estimating the alcohol concentration of the fuel, and the diagnosis condition by the abnormality diagnosis means is changed based on the alcohol concentration detected or estimated by the alcohol concentration determination means or In this configuration, diagnostic condition changing means for correction is provided.

  In this configuration, since the diagnostic conditions can be changed or corrected according to the alcohol concentration detected or estimated by the alcohol concentration determination means, the actual alcohol concentration can be obtained regardless of the alcohol concentration of the fuel. The abnormality diagnosis of the fuel level detector can be performed with high accuracy using the appropriate diagnosis conditions.

  Specifically, as in claim 2, the fuel consumption amount estimation means estimates a fuel consumption amount during a period until the intake air amount integrated value reaches a predetermined value, and the abnormality diagnosis means determines the intake air amount. A threshold is set based on the output change amount of the fuel level detector detected during a period until the integrated amount reaches a predetermined value, and the fuel consumption estimated by the fuel consumption estimation means is used as a diagnostic index. This may be compared with the threshold value to perform abnormality diagnosis of the fuel level detector.

  Alternatively, as in claim 3, the fuel consumption estimation means integrates the intake air amount during a predetermined period and based on the integrated value and the air-fuel ratio, the fuel consumption during the abnormality diagnosis period (hereinafter referred to as the fuel consumption amount during the abnormality diagnosis period) (Referred to as “first fuel consumption estimation value”), and the fuel consumption amount during the abnormality diagnosis period (hereinafter referred to as “the first fuel consumption amount estimated value”) based on the output change amount of the fuel level detector during the predetermined period. (Referred to as “second fuel consumption estimated value”), the first fuel consumption value is compared with the second fuel consumption estimated value, and the comparison result is used as a diagnostic index. May be compared with a threshold value to perform abnormality diagnosis of the fuel level detector.

  When changing or correcting the diagnostic conditions, the threshold value may be changed or corrected based on the alcohol concentration detected or estimated by the alcohol concentration determination means, as in claim 4. As in item 5, the diagnostic index may be changed or corrected based on the alcohol concentration detected or estimated by the alcohol concentration determination means.

  According to another aspect of the present invention, there is provided a means for diagnosing abnormality of the alcohol concentration determination means and means for prohibiting abnormality diagnosis of the fuel level detector when an abnormality of the alcohol concentration determination means is detected. It is also good. In this way, it is possible to prevent erroneous diagnosis of normality / abnormality of the fuel level detector when an abnormality occurs in the alcohol concentration determination means, and the reliability of abnormality diagnosis of the fuel level detector can be improved.

  According to a seventh aspect of the present invention, there is provided means for diagnosing abnormality of the alcohol concentration determination means, and when the abnormality of the alcohol concentration determination means is detected, the diagnosis condition is changed or corrected so as to widen the normal determination range. Anyway. In this way, it is possible to prevent a normal fuel level detector from being erroneously diagnosed as abnormal when an abnormality occurs in the alcohol concentration determination means, thereby improving the reliability of abnormality diagnosis of the fuel level detector.

  Specifically, as in claim 8, when an abnormality in the alcohol concentration determination means is detected, the diagnosis condition may be changed or corrected assuming that the alcohol concentration is 100%. Even in this case, the normal determination range can be expanded when an abnormality occurs in the alcohol concentration determination means, and it is possible to prevent a normal fuel level detector from being erroneously diagnosed as abnormal.

  According to another aspect of the present invention, the alcohol concentration determination means includes an alcohol concentration sensor that detects the alcohol concentration of the fuel, and an engine control parameter that varies under the influence of the alcohol concentration of the fuel (for example, an air-fuel ratio feedback correction amount, An alcohol concentration estimation means for estimating the alcohol concentration of the fuel based on a learning value, an air-fuel ratio deviation, a fuel pressure increase rate at the start, combustion stability, engine rotation fluctuation, and the like, and a means for diagnosing abnormality of the alcohol concentration sensor When the abnormality of the alcohol concentration sensor is not detected, the diagnostic condition is changed or corrected based on the alcohol concentration detected by the alcohol concentration sensor, and when the abnormality of the alcohol concentration sensor is detected, Based on the alcohol concentration estimated by the alcohol concentration estimation means, It may be changed or corrected cross conditions. In this way, even when an abnormality occurs in the alcohol concentration sensor, the diagnostic conditions can be changed or corrected using the alcohol concentration estimated by the alcohol concentration estimation means. The abnormality diagnosis of the fuel level detector can be performed with relatively high accuracy using the considered diagnosis conditions.

  Further, as in claim 10, a cooling water temperature detecting means for detecting the cooling water temperature of the engine may be provided, and the diagnosis condition may be changed or corrected in consideration of the cooling water temperature detected by the cooling water temperature detecting means. Thus, if the diagnosis condition is changed or corrected in consideration of the cooling water temperature, the correction amount of the fuel injection amount according to the cooling water temperature can be reflected in the diagnosis condition, and the accuracy of the abnormality diagnosis can be further improved. it can.

  Further, in consideration of the possibility that the alcohol concentration detected or estimated by the alcohol concentration determination means may fluctuate during the abnormality diagnosis period, as in claim 11, the alcohol concentration determination means includes the alcohol concentration during a predetermined period. Is obtained as the final alcohol concentration, or the first half alcohol concentration and the second half alcohol concentration in the predetermined period are detected or estimated, respectively, as in claim 12, and these values are obtained. From this, the final alcohol concentration may be obtained. Alternatively, as in the thirteenth aspect, the maximum and / or minimum value of the alcohol concentration during a predetermined period may be detected or estimated, and the final alcohol concentration may be obtained based on that value. In either case, the accuracy and reliability of the alcohol concentration detected or estimated by the alcohol concentration determination means can be improved.

  Several embodiments embodying the best mode for carrying out the present invention will be described below.

A first embodiment of the present invention will be described with reference to FIGS.
First, a schematic configuration of the entire engine control system will be described with reference to FIG.
An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11 that is an internal combustion engine, and an air flow meter 14 that detects the intake air amount is provided downstream of the air cleaner 13. A throttle valve 16 whose opening is adjusted by a motor 15 and a throttle opening sensor 17 for detecting the opening (throttle opening) of the throttle valve 16 are provided on the downstream side of the air flow meter 14.

  Further, a surge tank 18 is provided on the downstream side of the throttle valve 16, and an intake manifold 20 for introducing air into each cylinder of the engine 11 is provided in the surge tank 18. A fuel injection valve 21 for injecting fuel is attached in the vicinity of the intake port of the intake manifold 20 of each cylinder. An ignition plug 22 is attached to the cylinder head of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by spark discharge of the ignition plug 22 of each cylinder.

  On the other hand, the exhaust pipe 23 of the engine 11 is provided with an air-fuel ratio sensor 24 that detects the air-fuel ratio of the exhaust gas, and a catalyst 25 such as a three-way catalyst that purifies the exhaust gas is disposed downstream of the air-fuel ratio sensor 24. Is provided.

  A cooling water temperature sensor 26 (cooling water temperature detecting means) for detecting the cooling water temperature and a knock sensor 29 for detecting knocking are attached to the cylinder block of the engine 11. A crank angle sensor 28 that outputs a pulse signal every time the crankshaft 27 rotates by a predetermined crank angle is attached to the outer peripheral side of the crankshaft 27. Based on the output signal of the crank angle sensor 28, the crank angle and engine The rotation speed is detected.

  The engine 11 can use any of gasoline, alcohol such as ethanol and methanol, and alcohol mixed fuel obtained by mixing alcohol with gasoline as fuel, and any of these gasoline, alcohol, and alcohol mixed fuel can be used in the fuel tank 30. To refuel. A fuel pump 31 that pumps up fuel is provided in the fuel tank 30. The fuel discharged from the fuel pump 31 is sent to the delivery pipe 33 through the fuel pipe 32 and is distributed from the delivery pipe 33 to the fuel injection valve 21 of each cylinder. A fuel filter 34 and a pressure regulator 35 are connected in the vicinity of the fuel pump 31 in the fuel pipe 32, and the discharge pressure of the fuel pump 31 is regulated to a predetermined pressure by the pressure regulator 35, and surplus fuel exceeding that pressure The minute amount is returned into the fuel tank 30 by the fuel return pipe 36.

  Further, an alcohol concentration sensor 37 that detects an alcohol concentration of fuel (fuel discharged from the fuel pump 31) stored in the fuel tank 30 is disposed at an appropriate location (for example, the fuel pump 31) in the fuel tank 30. (Alcohol concentration determination means) is attached. Thus, if the alcohol concentration sensor 37 is installed in the fuel tank 30, even if fuel leaks from the alcohol concentration sensor 37 when the alcohol concentration sensor 37 fails, the fuel can be collected in the fuel tank 30. There is an advantage that fuel leakage to the outside can be prevented.

  However, the place where the alcohol concentration sensor 37 is attached is not limited to the fuel tank 30, and the alcohol concentration sensor 37 may be attached to the fuel pipe 32 or the delivery pipe 33. The alcohol concentration sensor 37 may use any configuration of the alcohol concentration sensor. For example, the alcohol concentration sensor 37 detects the alcohol concentration by measuring the capacitance according to the dielectric constant of the fuel. A sensor or an optical (transmission type) alcohol concentration sensor that measures the amount of light transmitted through the fuel (transmittance) to detect the alcohol concentration may be used.

  The fuel tank 30 is provided with a fuel level detector 39 that detects the fuel level (remaining amount of fuel) in the fuel tank 30. The output of the fuel level detector 39 and the outputs of the various sensors are input to a control circuit (hereinafter referred to as “ECU”) 38. The ECU 38 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium), so that the fuel injection amount of the fuel injection valve 21 according to the engine operating state and the like. The ignition timing of the spark plug 22 is controlled.

  At that time, considering that there is a relationship that the higher the alcohol concentration of the fuel, the lower the theoretical air-fuel ratio of the fuel, and the more fuel injection amount is required to control the actual air-fuel ratio to the theoretical air-fuel ratio. The ECU 38 executes a fuel injection control program (not shown) so that the fuel injection amount increases as the alcohol concentration of the fuel detected by the alcohol concentration sensor 37 increases, according to the alcohol concentration of the fuel. Correct the injection amount to increase or change / correct the target air-fuel ratio.

  Further, the ECU 38 executes a fuel level detector abnormality diagnosis program shown in FIG. 2 to be described later, thereby changing or correcting the diagnosis condition based on the alcohol concentration of the fuel detected by the alcohol concentration sensor 37, and integrating the intake air amount. The abnormality diagnosis of the fuel level detector 39 is executed based on the relationship between the fuel consumption estimated from the value and the output change amount of the fuel level detector 39.

In the first embodiment, abnormality diagnosis of the fuel level detector 39 is performed as follows.
First, the amount of intake air is integrated, and the fuel consumption during the period until the integrated value reaches a predetermined value is calculated based on the intake air amount integrated value (= predetermined value) and the air-fuel ratio.
Fuel consumption amount = intake air amount integrated value / air-fuel ratio Here, for example, a target air-fuel ratio of air-fuel ratio feedback control or an air-fuel ratio detected by the air-fuel ratio sensor 24 may be used as the air-fuel ratio.

  Further, a threshold value is calculated based on the output change amount of the fuel level detector 39 detected during the period until the intake air amount integrated value reaches a predetermined value and the alcohol concentration of the fuel detected by the alcohol concentration sensor 37. At this time, the fuel consumption is calculated from the output change amount of the fuel level detector 39, and a value obtained by correcting the fuel consumption amount according to the alcohol concentration is used as a threshold value, or the output change amount of the fuel level detector 39 is set. Alternatively, the threshold value may be calculated using a two-dimensional map using the alcohol concentration as a parameter.

Then, the fuel consumption amount calculated from the integrated value of the intake air amount is used as a “diagnosis index”, and this is compared with the threshold value to perform an abnormality diagnosis of the fuel level detector 39.
The abnormality diagnosis of the fuel level detector 39 of the first embodiment described above is executed by the ECU 38 as follows according to the fuel level detector abnormality diagnosis program of FIG.

  The fuel level detector abnormality diagnosis program in FIG. 2 is repeatedly executed at predetermined time intervals during engine operation. When this program is started, first, in step 101, it is determined whether or not an abnormality diagnosis execution condition is satisfied, for example, based on whether or not a predetermined time has elapsed since startup. Here, the reason that the abnormality diagnosis execution condition is that a predetermined time has elapsed since the start is that it takes a while for the residual fuel in the fuel tank 30 and the newly supplied fuel to be evenly mixed, and Since the fuel remaining in the fuel pipe 32 and the delivery pipe 33 (that is, the fuel whose alcohol concentration is not detected by the alcohol concentration sensor 37) is injected immediately after the first start after refueling, the alcohol detected by the alcohol concentration sensor 37 is detected. This is because the concentration (the alcohol concentration of the fuel in the fuel tank 30) and the alcohol concentration of the fuel injected from the fuel injection valve 21 may be different.

  If it is determined in step 101 that the abnormality diagnosis execution condition is not satisfied, the program is terminated without performing the subsequent processing.

On the other hand, if it is determined in step 101 that the abnormality diagnosis execution condition is satisfied, the process proceeds to step 102 where the intake air amount detected by the air flow meter 14 is integrated and the intake air amount integrated value (air consumption (Quantity). Thereafter, the routine proceeds to step 103, where the fuel consumption during the period until the intake air amount integrated value (air consumption amount) reaches a predetermined value is calculated based on the intake air amount integrated value (= predetermined value) and the air-fuel ratio. This fuel consumption is used as a diagnostic index.
Diagnostic index = fuel consumption = integrated intake air amount ÷ air-fuel ratio

  Here, as the air-fuel ratio, for example, a target air-fuel ratio of air-fuel ratio feedback control or an air-fuel ratio detected by the air-fuel ratio sensor 24 may be used. The processing of step 102 serves as fuel consumption estimation means in the claims.

  Thereafter, the routine proceeds to step 104, where it is determined whether or not the alcohol concentration sensor 37 is normal based on a diagnosis result of a self-diagnosis function (not shown) mounted on the vehicle. If a failure such as a disconnection or short circuit of the alcohol concentration sensor 37 is detected by the self-diagnosis function, the process proceeds to step 109, where abnormality diagnosis of the fuel level detector 39 is prohibited to prevent normal / abnormal determination.

  On the other hand, if it is determined in step 104 that the alcohol concentration sensor 37 is normal, the process proceeds to step 105 where the output change of the fuel level detector 39 detected during the period until the intake air amount integrated value reaches a predetermined value. The threshold value is calculated based on the amount and the alcohol concentration detected by the alcohol concentration sensor 37. At this time, the fuel consumption is calculated from the output change amount of the fuel level detector 39, and a value obtained by correcting the fuel consumption amount according to the alcohol concentration is used as a threshold value, or the output change amount of the fuel level detector 39 is set. Alternatively, the threshold value may be calculated using a two-dimensional map using the alcohol concentration as a parameter. Further, as shown in FIG. 3, the threshold value may be changed or corrected according to the cooling water temperature detected by the cooling water temperature sensor 26. In this way, the correction amount of the fuel injection amount according to the coolant temperature can be reflected in the threshold value (diagnostic condition), and the accuracy of abnormality diagnosis of the fuel level detector 39 can be improved. The processing in step 105 serves as diagnostic condition changing means in the claims.

  In step 105, a value obtained by averaging the detected values of the alcohol concentration sensor 37 during the abnormality diagnosis period may be used, or the first half alcohol concentration and the second half alcohol concentration during the abnormality diagnosis period may be detected. Alternatively, the higher (or lower) alcohol concentration may be selected, or the average value of both may be used as the final alcohol concentration detection value. Alternatively, the maximum value and / or the minimum value of the alcohol concentration during the abnormality diagnosis period may be detected, and the final alcohol concentration may be obtained based on the detected value.

  Thereafter, the process proceeds to step 106, the diagnosis index (fuel consumption) calculated in step 103 is compared with a threshold value, and if it is determined that the diagnosis index is smaller than the threshold value, the process proceeds to step 107, where the fuel level detector 39 is determined to be normal.

  On the other hand, if it is determined in step 106 that the diagnostic index is equal to or greater than the threshold value, the process proceeds to step 108 and it is determined that the fuel level detector 39 is abnormal. If it is determined that there is an abnormality, for example, a warning lamp (not shown) provided on the instrument panel of the driver's seat is turned on, or a warning display part (not shown) of the instrument panel of the driver's seat A warning is displayed to warn the driver, and the abnormality information (abnormality code, etc.) is rewritten to a rewritable non-volatile memory such as a backup RAM (not shown) of the ECU 38 (a rewrite that retains stored data even when the ECU 38 is powered off). Memory). The processing of these steps 106 to 108 serves as an abnormality diagnosis means in the claims.

  According to the first embodiment described above, since the threshold value (diagnostic condition) can be changed or corrected according to the alcohol concentration detected by the alcohol concentration sensor 37, what kind of alcohol concentration the fuel alcohol concentration is. However, the abnormality diagnosis of the fuel level detector 39 can be accurately performed using a threshold value (diagnostic condition) that matches the actual alcohol concentration.

  Moreover, in the first embodiment, when abnormality of the alcohol concentration sensor 37 is detected, abnormality diagnosis of the fuel level detector 39 is prohibited. It is possible to prevent erroneous diagnosis of normality / abnormality, and improve the reliability of abnormality diagnosis of the fuel level detector 39.

  In the second embodiment of the present invention, by executing the fuel level detector abnormality diagnosis program of FIG. 4, the fuel during the abnormality diagnosis period is based on the output change amount of the fuel level detector 39 during the predetermined abnormality diagnosis period. In addition to estimating the consumption (hereinafter referred to as “fuel consumption estimated value A”), the intake air amount is integrated during the abnormality diagnosis period, and the fuel consumption during the abnormality diagnosis period is based on the integrated value and the air-fuel ratio. Amount (hereinafter referred to as “fuel consumption estimated value B”), the former fuel consumption estimated value A and the latter fuel consumption estimated value B are compared, and the comparison result is used as a diagnostic index. Is compared with a threshold value set according to the alcohol concentration detected by the alcohol concentration sensor 37, so that an abnormality diagnosis of the fuel level detector 39 is performed. Other system configurations are the same as those in the first embodiment.

  The fuel level detector abnormality diagnosis program in FIG. 4 is repeatedly executed at predetermined time intervals during engine operation. When this program is started, first, in step 201, it is determined whether or not an abnormality diagnosis execution condition is satisfied, for example, whether or not a predetermined time has elapsed since the start, and the abnormality diagnosis execution condition is not satisfied. If it is determined, the program is terminated without performing the subsequent processing.

On the other hand, if it is determined in step 201 that the abnormality diagnosis execution condition is satisfied, the process proceeds to step 202, where the abnormality is detected based on the output change amount of the fuel level detector 39 during a predetermined abnormality diagnosis period. An estimated fuel consumption value A during the diagnosis period is calculated. Thereafter, the routine proceeds to step 203, where the intake air amount detected by the air flow meter 14 during the abnormality diagnosis period is integrated, and a fuel consumption estimated value B during the abnormality diagnosis period is calculated based on the integrated value and the air-fuel ratio. To do.
Fuel consumption estimation value B = intake air amount integrated value / air-fuel ratio Here, for example, the target air-fuel ratio of air-fuel ratio feedback control or the air-fuel ratio detected by the air-fuel ratio sensor 24 may be used as the air-fuel ratio.

Thereafter, the routine proceeds to step 204 where the absolute value of the difference between the fuel consumption estimated value A calculated from the output change amount of the fuel level detector 39 and the fuel consumption estimated value B calculated from the intake air amount integrated value | A−B | is calculated and used as a diagnostic index.
Diagnostic index = | A−B |

  Thereafter, the routine proceeds to step 205, where the control parameter of the air-fuel ratio feedback control that changes due to the influence of the alcohol concentration of the fuel (for example, the air-fuel ratio feedback correction amount, its learning value, the air-fuel ratio deviation amount, the target air-fuel ratio and the actual air-fuel ratio Based on the ratio, the alcohol concentration estimate of the fuel is calculated. The method for estimating the alcohol concentration of the fuel is not limited to the control parameter of the air-fuel ratio feedback control, but based on any one of the fuel pressure increase rate at the start, combustion stability (engine rotation fluctuation), engine torque, etc. The concentration may be estimated. In short, the estimated value of the alcohol concentration of the fuel may be calculated based on the engine control parameter that changes due to the influence of the alcohol concentration of the fuel.

  Thereafter, the process proceeds to step 206, where the alcohol concentration sensor determines whether or not the absolute value of the difference between the alcohol concentration detected by the alcohol concentration sensor 37 and the estimated alcohol concentration value calculated in step 205 is smaller than a predetermined determination threshold value. It is determined whether or not 37 is normal. At this time, after confirming that a failure such as disconnection or short-circuit of the alcohol concentration sensor 37 is not detected by a self-diagnosis function (not shown) mounted on the vehicle, the difference between the detected value and the estimated value of the alcohol concentration The normality / abnormality of the alcohol concentration sensor 37 may be determined based on the absolute value.

  If it is determined in step 206 that the alcohol concentration sensor 37 is abnormal, the process proceeds to step 211, and abnormality diagnosis of the fuel level detector 39 is prohibited.

  On the other hand, if it is determined in step 206 that the alcohol concentration sensor 37 is normal, the process proceeds to step 207, where a threshold value is calculated based on the alcohol concentration of the fuel detected by the alcohol concentration sensor 37. At this time, the threshold value may be changed or corrected according to the coolant temperature detected by the coolant temperature sensor 26. Specifically, using a two-dimensional map (see FIG. 3) that calculates the threshold value with the alcohol concentration of the fuel and the cooling water temperature as parameters, the threshold value corresponding to the current alcohol concentration and cooling water temperature is calculated, or You may correct | amend the threshold set with the map etc. according to alcohol concentration according to cooling water temperature.

  Thereafter, the process proceeds to step 208, and the diagnosis index | AB | calculated in step 204 is compared with a threshold value. If it is determined that the diagnosis index | AB | is smaller than the threshold value, the process proceeds to step 209. Then, it is determined that the fuel level detector 39 is normal. On the other hand, if it is determined in step 208 that the diagnostic index | AB | is equal to or greater than the threshold value, the process proceeds to step 210 and it is determined that the fuel level detector 39 is abnormal.

  Also in the second embodiment described above, the same effect as in the first embodiment can be obtained.

In the first and second embodiments, the abnormality diagnosis of the fuel level detector 39 is prohibited when the abnormality of the alcohol concentration sensor 37 is detected. However, in the third embodiment of the present invention, the fuel level detection of FIG. When the abnormality of the alcohol concentration sensor 37 is detected by executing the engine abnormality diagnosis program, the threshold value is calculated according to the alcohol concentration estimated based on the engine control parameter that changes due to the influence of the alcohol concentration of the fuel. Yes.
The fuel level detector abnormality diagnosis program in FIG. 5 is merely a change of the process in step 211 of the fuel level detector abnormality diagnosis program in FIG.

  In the fuel level detector abnormality diagnosis program of FIG. 5, if an abnormality of the alcohol concentration sensor 37 is detected in step 206, the process proceeds to step 212, and based on the engine control parameter that changes due to the influence of the alcohol concentration of fuel in step 205. The threshold value corresponding to the estimated alcohol concentration value is calculated using a map or the like. At this time, the threshold value may be changed or corrected according to the coolant temperature detected by the coolant temperature sensor 26. The process of each step other than this is the same as the process of each step of FIG.

  In the third embodiment, when the abnormality of the alcohol concentration sensor 37 is detected, the threshold value corresponding to the estimated alcohol concentration value calculated based on the engine control parameter that changes due to the influence of the alcohol concentration of the fuel is calculated. Even when an abnormality occurs in the alcohol concentration sensor 37, the abnormality diagnosis of the fuel level detector 39 can be performed with relatively high accuracy using a threshold value corresponding to the estimated alcohol concentration value.

  In the third embodiment, when the abnormality of the alcohol concentration sensor 37 is detected, the threshold value is calculated according to the estimated alcohol concentration value. However, in the fourth embodiment of the present invention, the fuel level detector abnormality of FIG. By executing the diagnostic program, when an abnormality of the alcohol concentration sensor 37 is detected in step 206, the process proceeds to step 213, and the alcohol concentration detection value is set to a predetermined concentration so as to widen the normal determination range. Here, the predetermined concentration may be, for example, an alcohol concentration of 100% or a lower concentration, and in short, it may be set so as to widen the normal determination range. Thereafter, the process proceeds to step 207, where a threshold value is calculated based on the alcohol concentration detected by the alcohol concentration sensor 37 or the predetermined concentration set in step 213. The process of each step other than this is the same as the process of each step of FIG.

  In the fourth embodiment, when an abnormality of the alcohol concentration sensor 37 is detected, the alcohol concentration detection value is set to a predetermined concentration so as to widen the normal determination range. Therefore, it is possible to prevent the fuel level detector 39 from being erroneously diagnosed as abnormal, and to improve the reliability of the abnormality diagnosis of the fuel level detector 39.

  In any of the first to fourth embodiments, the threshold value is changed or corrected according to the alcohol concentration detected by the alcohol concentration sensor 37. However, in the fifth embodiment of the present invention, the fuel level detector abnormality of FIG. By executing the diagnostic program, when it is determined in step 206 that the alcohol concentration sensor 37 is normal, the process proceeds to step 207a, and the diagnosis index | AB | calculated in step 204 is used as the alcohol concentration sensor 37. Correction is made according to the alcohol concentration detected in. At this time, the diagnosis index | AB | may be corrected in consideration of the coolant temperature detected by the coolant temperature sensor 26.

  Thereafter, the process proceeds to step 208, and the diagnostic index | A-B | corrected in step 207a is compared with a preset threshold value. This threshold value may be set to a threshold value according to a predetermined reference alcohol concentration (for example, 0%, 50%, 100%, etc.).

  If it is determined in step 208 that the diagnostic index | A−B | is smaller than the threshold value, the process proceeds to step 209 to determine that the fuel level detector 39 is normal. On the other hand, if it is determined in step 208 that the diagnostic index | AB | is equal to or greater than the threshold value, the process proceeds to step 210 and it is determined that the fuel level detector 39 is abnormal. The process of each step other than this is the same as the process of each step of FIG.

  Also in the fifth embodiment described above, the same effect as in the second embodiment can be obtained. In the fifth embodiment, when an abnormality of the alcohol concentration sensor 37 is detected in step 206, the process proceeds to step 211 to prohibit abnormality diagnosis of the fuel level detector 39. However, the alcohol concentration sensor 37 When the abnormality is detected, the diagnostic index | A-B | is corrected according to the estimated alcohol concentration calculated in step 205, or when the abnormality of the alcohol concentration sensor 37 is detected, the alcohol concentration detection value is set to the normal determination range. A predetermined density (for example, 100%) may be set so as to increase, and the diagnostic index | AB | may be corrected according to the predetermined density.

[Other Examples]
In each of the first to fifth embodiments, the diagnosis condition (threshold value or diagnostic index) is changed or corrected according to the alcohol concentration detected by the alcohol concentration sensor 37. However, the vehicle is not equipped with the alcohol concentration sensor 37. When the present invention is applied, an engine control parameter (for example, an air-fuel ratio feedback correction amount, a learning value thereof, an air-fuel ratio deviation amount, a fuel pressure increase rate at start-up, combustion stability, It is also possible to estimate the alcohol concentration of the fuel based on the engine rotation fluctuation, etc., and to change or correct the diagnostic conditions (threshold value or diagnostic index) according to the estimated alcohol concentration.

  Further, in each of the second to fifth embodiments, the difference between the fuel consumption estimated value A calculated from the output change amount of the fuel level detector 39 and the fuel consumption estimated value B calculated from the intake air amount integrated value is calculated. The absolute value | A−B | is calculated and used as a diagnostic index. The ratio (A / B) of the former fuel consumption estimated value A and the latter fuel consumption estimated value B is used as a diagnostic index. May be compared with a threshold value to perform abnormality diagnosis of the fuel level detector 39.

  Alternatively, the output change amount of the fuel level detector 39 is estimated based on the estimated fuel consumption amount B calculated from the intake air amount integrated value during the abnormality diagnosis period (or the intake air amount integrated value during the abnormality diagnosis period). The amount of change in the output of the fuel level detector 39 is estimated from a map or a mathematical formula), and the difference value or ratio between the estimated amount of change in the output of the fuel level detector 39 and the actual amount of change in output is used as a diagnostic index. May be compared with a threshold value to perform abnormality diagnosis of the fuel level detector 39.

  Further, when the relationship between the output change amount of the fuel level detector 39 and the estimated fuel consumption amount changes depending on the fuel level in the fuel tank 30 (that is, when the peripheral side surface shape of the fuel tank 30 changes depending on the height position). Alternatively, the relationship (map or mathematical expression) between the output change amount of the fuel level detector 39 and the estimated fuel consumption amount may be corrected in accordance with the fuel level detected by the fuel level detector 39.

  In addition, the present invention is not limited to the intake port injection type engine as shown in FIG. 1, but includes an in-cylinder injection type engine, and both an intake port injection fuel injection valve and an in-cylinder injection fuel injection valve. It can also be applied to dual-injection engines.

It is a schematic block diagram of the whole engine control system common to Examples 1-5 of this invention. It is a flowchart which shows the flow of a process of the fuel level detector abnormality diagnosis program of Example 1. FIG. It is a figure explaining the relationship between the alcohol concentration of a fuel, cooling water temperature, and a threshold value. It is a flowchart which shows the flow of a process of the fuel level detector abnormality diagnosis program of Example 2. FIG. It is a flowchart which shows the flow of a process of the fuel level detector abnormality diagnosis program of Example 3. It is a flowchart which shows the flow of a process of the fuel level detector abnormality diagnosis program of Example 4. It is a flowchart which shows the flow of a process of the fuel level detector abnormality diagnosis program of Example 5.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 14 ... Air flow meter, 15 ... Motor, 16 ... Throttle valve, 17 ... Throttle opening sensor, 21 ... Fuel injection valve, 22 ... Spark plug, 23 ... Exhaust pipe, DESCRIPTION OF SYMBOLS 24 ... Air-fuel ratio sensor, 25 ... Catalyst, 26 ... Cooling water temperature sensor (cooling water temperature detection means), 28 ... Crank angle sensor, 30 ... Fuel tank, 31 ... Fuel pump, 32 ... Fuel piping, 33 ... Delivery pipe, 34 ... Fuel filter, 35 ... Pressure regulator, 37 ... Alcohol concentration sensor (alcohol concentration determination means), 38 ... ECU (abnormality diagnosis means, diagnostic condition changing means), 39 ... Fuel level detector

Claims (13)

A fuel level detector for detecting the fuel level in the fuel tank;
Fuel consumption estimation means for integrating the intake air amount and estimating the fuel consumption from the integrated value;
An abnormality diagnosing unit for diagnosing an abnormality of the fuel level detector based on a relationship between a fuel consumption estimated by the fuel consumption estimating unit and an output change amount of the fuel level detector; In the abnormality diagnosis device,
Alcohol concentration determination means for detecting or estimating the alcohol concentration of the fuel;
An abnormality diagnosis device for a fuel level detector, comprising: diagnosis condition changing means for changing or correcting a diagnosis condition by the abnormality diagnosis means based on the alcohol concentration detected or estimated by the alcohol concentration determination means. The fuel consumption estimation means estimates the fuel consumption during a period until the intake air amount integrated value reaches a predetermined value,
The abnormality diagnosis means sets a threshold based on an output change amount of the fuel level detector detected during a period until the intake air amount integrated value reaches a predetermined value, and the fuel estimated by the fuel consumption estimation means The abnormality diagnosis device for a fuel level detector according to claim 1, wherein the abnormality diagnosis of the fuel level detector is performed by using consumption as a diagnostic index and comparing it with the threshold value. The fuel consumption amount estimation means integrates the intake air amount during a predetermined period and based on the integrated value and the air-fuel ratio, the fuel consumption amount during the abnormality diagnosis period (hereinafter referred to as “first fuel consumption amount estimated value”). Estimated)
The abnormality diagnosis means estimates a fuel consumption amount during the abnormality diagnosis period (hereinafter referred to as “second fuel consumption estimated value”) based on an output change amount of the fuel level detector during the predetermined period; The first fuel consumption value is compared with the second fuel consumption estimated value, and the comparison result is used as a diagnostic index, which is compared with a threshold value to perform abnormality diagnosis of the fuel level detector. The abnormality diagnosis device for a fuel level detector according to claim 1.   The diagnostic condition changing means changes or corrects the diagnostic condition by changing or correcting the threshold based on the alcohol concentration detected or estimated by the alcohol concentration determination means. The abnormality diagnosis device for the fuel level detector as described.   The diagnostic condition changing means changes or corrects the diagnostic condition by changing or correcting the diagnostic index based on the alcohol concentration detected or estimated by the alcohol concentration determination means. An abnormality diagnosis device for a fuel level detector according to claim 1.   The apparatus includes: means for diagnosing abnormality of the alcohol concentration determination means; and means for prohibiting abnormality diagnosis of the fuel level detector when an abnormality of the alcohol concentration determination means is detected. The abnormality diagnosis device for a fuel level detector according to any one of 1 to 5. Means for performing an abnormality diagnosis of the alcohol concentration determination means;
6. The diagnostic condition changing unit according to claim 1, wherein the diagnostic condition is changed or corrected so as to widen the normal determination range when an abnormality of the alcohol concentration determination unit is detected. An abnormality diagnosis device for fuel level detectors.   8. The fuel level according to claim 7, wherein the diagnosis condition changing means changes or corrects the diagnosis condition on the assumption that the alcohol concentration is 100% when an abnormality of the alcohol concentration determination means is detected. Detector abnormality diagnosis device. The alcohol concentration determination means includes an alcohol concentration sensor that detects the alcohol concentration of the fuel, an alcohol concentration estimation means that estimates the alcohol concentration of the fuel based on an engine control parameter that varies under the influence of the alcohol concentration of the fuel, Means for diagnosing abnormality of the alcohol concentration sensor,
The diagnostic condition changing means changes or corrects the diagnostic condition based on the alcohol concentration detected by the alcohol concentration sensor when no abnormality of the alcohol concentration sensor is detected, and the abnormality of the alcohol concentration sensor is detected. 6. The abnormality diagnosis device for a fuel level detector according to claim 1, wherein the diagnosis condition is changed or corrected based on the alcohol concentration estimated by the alcohol concentration estimation means. Equipped with cooling water temperature detecting means for detecting the cooling water temperature of the engine,
10. The fuel level detector according to claim 1, wherein the diagnostic condition changing unit changes or corrects the diagnostic condition in consideration of a cooling water temperature detected by the cooling water temperature detecting unit. Abnormality diagnosis device.   11. The fuel level detector abnormality diagnosis according to claim 1, wherein the alcohol concentration determination means obtains a value obtained by averaging the alcohol concentrations during the predetermined period as a final alcohol concentration. apparatus.   11. The alcohol concentration determination means detects or estimates an alcohol concentration in the first half and an alcohol concentration in the latter half during a predetermined period, and obtains a final alcohol concentration from these values. An abnormality diagnosis device for a fuel level detector according to claim 1.   11. The alcohol concentration determination means detects or estimates a maximum value and / or a minimum value of an alcohol concentration during a predetermined period, and obtains a final alcohol concentration based on the detected value. The abnormality diagnosis device for a fuel level detector according to any one of the above.

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