JP4467783B2 - Failure diagnosis device for fuel temperature sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel temperature sensor failure diagnosis device that diagnoses abnormality of a fuel temperature sensor that detects the temperature of fuel in a fuel tank.
[0002]
[Prior art]
In general, a vehicle such as an automobile using an engine as a driving power source employs various technologies for engine control in order to prevent air pollution and save resources, and one of them is fuel generated in a fuel tank. In order to prevent the evaporated gas (evaporative gas) from being discharged into the atmosphere, the evaporated fuel gas is adsorbed by activated carbon in the canister and temporarily stored, and the evaporated gas in the canister is sucked into the engine combustion chamber from the intake passage under the set operating conditions. There is a so-called evaporation purge device.
[0003]
Conventionally, failure diagnosis of the evaporation purge device has been performed by detecting changes in the fuel pressure, but in recent years, accurate diagnosis has been made by measuring the temperature of the fuel in the fuel tank and estimating the amount of evaporation gas generated. Technology to do is being adopted. For this reason, if an abnormality occurs in the sensor for detecting the fuel temperature itself, the reliability of the failure diagnosis of the evaporation purge device is lowered, so that a failure diagnosis of the fuel temperature sensor is required.
[0004]
Conventionally, as temperature sensor failure diagnosis, there is an engine temperature sensor failure diagnosis technique disclosed in Japanese Patent Application Laid-Open No. 11-351976. In this prior art, when the degree of change in temperature sensor output is within a predetermined level, It is determined that the temperature sensor is abnormal.
[0005]
[Problems to be solved by the invention]
However, since the temperature change of the fuel temperature is usually smaller than that of the engine temperature disclosed in the prior art, an erroneous determination is generated simply by monitoring the output change of the fuel temperature sensor and diagnosing the abnormality.
[0006]
The present invention has been made in view of the above circumstances, and when diagnosing an abnormality of a fuel temperature sensor that detects the temperature of the fuel in the fuel tank, it reliably captures the state in which the fuel temperature changes, and prevents erroneous determination. An object of the present invention is to provide a fuel temperature sensor failure diagnosis device capable of improving the reliability of diagnosis.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, an invention according to claim 1 is a fuel temperature sensor failure diagnosis device for diagnosing abnormality of a fuel temperature sensor for detecting the temperature of fuel in the fuel tank, wherein the fuel in the fuel tank is detected. A fuel level sensor for detecting the fuel level, and a change amount of the fuel level detected by the fuel level sensor is not less than a set value and a change amount of the fuel temperature detected by the fuel temperature sensor is not more than a diagnosis judgment value And an abnormality determining means for determining that the fuel temperature sensor is abnormal.
[0008]
According to a second aspect of the present invention, in the first aspect of the invention, the abnormality determining means detects the amount of change in the fuel level detected by the fuel level sensor not less than the set value and detected by the fuel temperature sensor. The number of times the amount of change in the fuel temperature is equal to or less than the diagnosis determination value is counted, and when the counted value exceeds the set number of times, it is determined that the fuel temperature sensor is abnormal.
[0009]
According to a third aspect of the invention, in the first or second aspect of the invention, the set value is a value capable of determining that the change in the fuel level in the fuel tank is due to refueling the fuel tank. It is characterized by doing.
[0010]
According to a fourth aspect of the present invention, there is provided a fuel temperature sensor failure diagnosis device for diagnosing abnormality of a fuel temperature sensor for detecting the temperature of fuel in the fuel tank, wherein the fuel level sensor detects the level of fuel in the fuel tank. An intake air amount detection means for detecting the intake air amount of the engine directly or by estimation, and a change amount of the fuel temperature detected by the fuel temperature sensor is less than or equal to a diagnostic judgment value, and the intake air amount detection means And an abnormality determining means for determining that the fuel temperature sensor is abnormal when the integrated value of the intake air amount detected by the step is equal to or greater than a set value.
[0011]
According to a fifth aspect of the invention, in the fourth aspect of the invention, the set value is a value equal to or greater than an integrated value of the intake air amount proportional to the capacity of the fuel tank.
[0012]
That is, the invention according to claim 1 detects the level of fuel in the fuel tank, and the detected change amount of the fuel level is equal to or greater than a set value, and the change amount of the fuel temperature detected by the fuel temperature sensor is diagnosed. If it is equal to or less than the determination value, it is determined that the fuel temperature sensor is abnormal, so that a state in which the fuel temperature changes can be surely captured to prevent erroneous determination and improve diagnosis reliability. In this case, the invention according to claim 2 counts the number of times that the change amount of the fuel level is not less than the set value and the detected change amount of the fuel temperature is not more than the diagnosis judgment value, and the count value indicates the set number of times. If the fuel temperature sensor is exceeded, it is determined that the fuel temperature sensor is abnormal, thereby further improving the reliability of diagnosis. According to a third aspect of the present invention, the set value is set to a value by which it can be determined that the change in the fuel level in the fuel tank is due to fuel supply to the fuel tank. Diagnosis is possible.
[0013]
According to a fourth aspect of the present invention, the amount of change in the fuel temperature detected by the fuel temperature sensor is less than or equal to the diagnostic determination value, and the integrated value of the intake air amount detected by the intake air amount detection means is greater than or equal to the set value. In this case, by determining that the fuel temperature sensor is abnormal, it is possible to reliably capture a state in which the fuel temperature changes, prevent erroneous determination, and improve diagnosis reliability. In this case, the invention according to claim 5 enables diagnosis at the time of refueling with a large fuel temperature change by setting the set value to a value equal to or greater than the integrated value of the intake air amount proportional to the capacity of the fuel tank.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. 1 to 5 relate to a first embodiment of the present invention, FIG. 1 is an explanatory view showing a fuel system of an engine, FIG. 2 is a flowchart of a fuel temperature sensor diagnosis routine, FIG. 3 is a time chart of diagnosis at the time of refueling, FIG. 4 is a time chart for diagnosis during travel (OK determination), and FIG. 5 is a time chart for diagnosis during travel (NG determination).
[0015]
In FIG. 1, reference numeral 1 denotes an engine. A throttle valve 3 is interposed in an intake pipe 2 of the engine 1. An air flow sensor (intake air amount sensor) such as a hot wire type or a hot film type is provided upstream of the throttle valve 3. ) 4 is provided. An injector 5 is disposed downstream of the throttle valve 3. The injector 5 is pumped from a fuel pump 7 disposed in the fuel tank 6 and adjusted to a predetermined set pressure by a pressure regulator 8. Pressurized fuel is supplied.
[0016]
The fuel tank 6 is provided with a float type fuel level sensor 9 for detecting the fuel level in the tank, and in the vicinity of the fuel suction port of the fuel pump 7, the fuel in the fuel tank 6 is detected. A fuel temperature sensor 10 is attached to detect the temperature. The air flow sensor 4, the fuel level sensor 9, and the fuel temperature sensor 10 are connected to an electronic control unit (ECU) 20 including a microcomputer or the like, and an abnormality of the fuel temperature sensor 10 is diagnosed by a diagnostic function of the ECU 20. If an abnormality occurs, an alarm signal is output from the ECU 20 to the alarm device 21 to issue an alarm.
[0017]
Hereinafter, the diagnosis process of the fuel temperature sensor 10 by the ECU 20 will be described with reference to the flowchart of FIG. The fuel temperature sensor 10 is initially diagnosed when the ignition switch is turned on. In this initial diagnosis, an abnormality determination counter (NG counter) CNG described below is once set, and when the output of the fuel temperature sensor 10 exceeds a predetermined value, it is determined to be normal and the NG counter CNG is cleared. Then, after the system is operated, the fuel temperature sensor diagnostic routine of FIG. 2 is executed every predetermined time.
[0018]
In the fuel temperature sensor diagnostic routine, first, in step S1, it is checked whether or not a condition that the amount of change in the fuel level in the fuel tank 6 is equal to or greater than a set value is satisfied based on a signal from the fuel level sensor 9. This condition is a condition for making a diagnosis of the fuel temperature sensor 10 by surely capturing a state in which the fuel temperature changes. The fuel in the fuel tank 6 is reduced against a decrease in the fuel level due to fuel consumption while the vehicle is running. The temperature rises due to agitation (circulation) by the fuel pump 7, heat reception around the engine, etc., and the temperature drops when new fuel is replenished by refueling. Therefore, by detecting the change in the fuel level in the fuel tank 6 and making a diagnosis, the abnormality of the fuel temperature sensor 10 can be reliably detected.
[0019]
In this case, the set value for checking the diagnosis condition may be a value corresponding to one of traveling and refueling, but prior to execution of this routine so that diagnosis can be performed both during traveling and refueling. It is desirable to determine in advance when traveling and when refueling, and select a value corresponding to when traveling and a value corresponding to when refueling, and set it to a set value. For example, the rate of change of the fuel level per hour is obtained to determine when the vehicle is traveling and when the fuel is supplied, and a value that can determine that the change in the fuel level in the fuel tank 6 is due to the fuel supply to the fuel tank 6 A value that can be determined to be due to fuel consumption during travel is selected and set in advance. The set value for determining refueling is set to a value corresponding to, for example, 5 liters or 10 liters in consideration of the capacity of the fuel tank 6 or the fuel consumption of the vehicle. It is set in consideration of engine displacement and type, fuel consumption, engine load, vehicle speed, shift position, and the like.
[0020]
In step S1, if the change amount of the fuel level has not reached the set value, the routine is exited, and if the change amount of the fuel level is not less than the set value, the process proceeds to step S2 and the fuel temperature sensor 10 It is checked whether or not the amount of change in fuel temperature based on the output is greater than or equal to the diagnostic judgment value. That is, a temperature change width of the fuel corresponding to a decrease in fuel during driving or an increase in fuel due to refueling is obtained in advance, and a slight margin is added to this temperature change width to obtain a diagnosis determination value. Then, by comparing this diagnosis determination value with the amount of change in the fuel temperature actually measured by the fuel temperature sensor 10, it is diagnosed whether or not the fuel temperature sensor 10 is normal.
[0021]
As a result, if the amount of change in the fuel temperature measured by the fuel temperature sensor 10 is greater than or equal to the diagnosis determination value, the process proceeds from step S2 to step S3 to clear the NG counter CNG (CNG ← 0). The temperature sensor 10 is determined to be normal (OK determination), and the routine is exited. Further, when the change amount of the fuel temperature measured by the fuel temperature sensor 10 does not reach the diagnosis determination value, the fuel temperature sensor 10 may be abnormal, so the process proceeds from step S2 to step S5 and the NG counter is reached. CNG is incremented (CNG ← CNG + 1), and it is checked in step S6 whether or not the NG counter CNG has exceeded the set number of times.
[0022]
If the NG counter CNG has not reached the set number of times, the process returns to step S1 to continue the above processing. If the NG counter CNG exceeds the set number of times, the fuel temperature sensor 10 has failed in step S7. If it is determined that there is an NG, the routine is exited by issuing an alarm via the alarm device 21 or the like. That is, when the change in the fuel temperature is small with respect to the decrease in the fuel level due to the fuel consumption during traveling, or the fuel temperature in the fuel supply and the temperature of the fuel in the fuel tank 6 are substantially equal, Since the temperature of the fuel does not change so much, it is determined that the fuel temperature sensor 10 is faulty only when the NG determination is made a plurality of times, thereby ensuring diagnosis reliability and avoiding erroneous determination.
[0023]
FIG. 3 is a time chart in the case of diagnosing the fuel temperature sensor 10 by capturing the fuel level change due to refueling. When the fuel level rises in response to a decrease in the fuel level and new fuel is replenished by refueling, the fuel The fuel temperature in the tank 6 decreases. Accordingly, if the fuel temperature measured by the fuel temperature sensor 10 changes corresponding to the change in the fuel level, the fuel temperature sensor 10 is determined to be normal and an OK determination is made. When normal, the NG counter CNG is repeatedly set and cleared. On the other hand, when the fuel temperature measured by the fuel temperature sensor 10 does not change in response to the change in the fuel level, the NG counter CNG is incremented, and when the set number of times is reached, it is assumed that the fuel temperature sensor 10 has failed. An NG determination is made.
[0024]
4 and 5 are time charts when the fuel temperature sensor 10 is diagnosed by capturing changes in the fuel level during traveling. As shown in FIG. 4, the fuel level gradually increases as the fuel is consumed during traveling. If the fuel temperature measured by the fuel temperature sensor 10 gradually rises correspondingly, the fuel temperature sensor 10 determines that the fuel temperature sensor 10 is normal, and clears the NG counter CNG. On the other hand, as shown in FIG. 5, if the measured value of the fuel temperature does not change because the output of the fuel temperature sensor 10 is stuck (fixed) even if the decrease in the fuel level reaches the set value, the NG counter When CNG is incremented and reaches the set number of times, an NG determination is made that the fuel temperature sensor 10 is out of order.
[0025]
That is, instead of simply monitoring the output change of the fuel temperature sensor 10 and diagnosing the abnormality, the abnormality of the fuel temperature sensor 10 is diagnosed based on whether or not there is a change in the fuel temperature corresponding to the change in the fuel level. Abnormalities can be reliably detected without causing erroneous determination, and the quality of diagnosis can be improved.
[0026]
6 and 7 relate to the second embodiment of the present invention, FIG. 6 is a flowchart of a fuel temperature sensor diagnosis routine, and FIG. 7 is a time chart of diagnosis.
[0027]
The second form uses an integrated value of the intake air amount of the engine 1 as a parameter corresponding to the amount of change in the fuel level, compared to the first form described above. That is, a decrease in the fuel level in the fuel tank 6 due to fuel consumption during travel (a decrease in fuel) can be grasped by the intake air amount that is proportional to the fuel consumption amount. Therefore, together with the ignition switch ON, the intake air amount is integrated based on the signal from the air flow sensor 4, and when the integrated value of the intake air amount exceeds the set value, the fuel temperature does not rise to the diagnosis determination value. In this case, it is determined that the fuel temperature sensor 10 is abnormal.
[0028]
For this reason, in the fuel temperature sensor diagnosis routine of the second embodiment shown in FIG. 6, first, it is checked in step S10 whether or not the change amount of the fuel temperature measured by the fuel temperature sensor 10 is greater than or equal to the diagnosis determination value. The diagnosis determination value here is a value obtained by previously obtaining a change range of the fuel temperature corresponding to the change in the fuel amount corresponding to the set value in step S11 below, and adding a slight margin to this temperature change range.
[0029]
If the change amount of the fuel temperature does not reach the diagnosis determination value, the process proceeds from step S10 to step S12, and it is checked whether or not the integrated value of the intake air amount measured by the air flow sensor 4 is equal to or greater than the set value. . This set value is an integrated value of the intake air amount corresponding to the fuel change amount that can reliably capture the temperature change of the fuel. In this case, by setting the set value to a value equal to or greater than the integrated value proportional to the capacity of the fuel tank 6, it is possible to capture the change in fuel temperature due to fueling.
[0030]
As a result, when the integrated value of the intake air amount has not reached the set value, the process returns to step S10 and the process is continued. Thereafter, when the change amount of the fuel temperature becomes equal to or greater than the diagnosis determination value, the process proceeds from step S10 to step S12, where it is determined that the fuel temperature sensor 10 is normal (OK determination) (see FIG. 7A), and the intake air amount Clear accumulated value and exit routine. On the other hand, if the integrated value of the intake air amount becomes greater than or equal to the set value in step S11 without the change amount of the fuel temperature reaching the diagnosis determination value in step S1, the fuel temperature sensor 10 is determined to be abnormal and step S13. NG determination is made (see FIG. 7B), and the routine exits by issuing an alarm via the alarm device 21 or the like.
[0031]
In the second mode, as in the first mode, it is possible not only to diagnose the abnormality of the fuel temperature sensor 10 without causing erroneous determination, but also to be influenced by the load and the operating state that change from time to time. Stable diagnosis can be performed.
[0032]
In the second embodiment, the intake air amount is directly detected by the air flow sensor 4, but the present invention is not limited to this. For example, based on the engine speed and the throttle opening, and the fuel injection width of the injector The intake air amount may be estimated based on (amount) and the throttle opening.
[0033]
【The invention's effect】
As described above, according to the present invention, when diagnosing an abnormality in the fuel temperature sensor that detects the temperature of the fuel in the fuel tank, it is possible to reliably detect the state in which the fuel temperature changes and prevent erroneous determination, Reliability can be improved.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a fuel system of an engine according to a first embodiment of the present invention. FIG. 2 is a flowchart of a fuel temperature sensor diagnostic routine. FIG. 3 is a time chart of a diagnosis at the time of refueling. 4) Same as above, time chart of running diagnosis (OK judgment) [FIG. 5] Same as above, Time chart of running time diagnosis (NG judgment) [FIG. 6] A fuel temperature sensor diagnostic routine according to the second embodiment of the present invention. Flow chart [Fig. 7] Same as above, diagnosis time chart [Explanation of symbols]
6 Fuel tank 9 Fuel level sensor 10 Fuel temperature sensor 20 ECU

Claims (5)

A fuel temperature sensor failure diagnosis device for diagnosing abnormality of a fuel temperature sensor for detecting the temperature of fuel in a fuel tank,
A fuel level sensor for detecting the level of fuel in the fuel tank;
The fuel temperature sensor is abnormal when the amount of change in the fuel level detected by the fuel level sensor is greater than or equal to a set value and the amount of change in the fuel temperature detected by the fuel temperature sensor is less than or equal to a diagnostic determination value. A fuel temperature sensor failure diagnosis device comprising: an abnormality determination means for determining The abnormality determination means is
Count the number of times the amount of change in the fuel level detected by the fuel level sensor is greater than or equal to the set value and the amount of change in the fuel temperature detected by the fuel temperature sensor is less than or equal to the diagnostic determination value. 2. The fuel temperature sensor failure diagnosis apparatus according to claim 1, wherein the fuel temperature sensor determines that the fuel temperature sensor is abnormal when the number of times exceeds a predetermined number. The failure of the fuel temperature sensor according to claim 1 or 2, wherein the set value is a value by which it can be determined that the change in fuel level in the fuel tank is due to refueling to the fuel tank. Diagnostic device. A fuel temperature sensor failure diagnosis device for diagnosing abnormality of a fuel temperature sensor for detecting the temperature of fuel in a fuel tank,
A fuel level sensor for detecting the level of fuel in the fuel tank;
Intake air amount detection means for detecting the intake air amount of the engine directly or by estimation; and
When the amount of change in fuel temperature detected by the fuel temperature sensor is less than or equal to a diagnostic determination value and the integrated value of intake air amount detected by the intake air amount detection means is greater than or equal to a set value, the fuel temperature sensor An apparatus for diagnosing a failure of a fuel temperature sensor, comprising: an abnormality determination unit that determines that the fuel is abnormal. 5. The fuel temperature sensor failure diagnosis apparatus according to claim 4, wherein the set value is set to a value equal to or greater than an integrated value of the intake air amount proportional to the capacity of the fuel tank.

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