JP2002188527A - Trouble diagnostic device for fuel temperature sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent erroneous decision by surely catching a condition changing a fuel temperature so as to improve reliability of diagnosis, in the case of diagnosing abnormality of a fuel temperature sensor detecting a temperature of fuel in a fuel tank. SOLUTION: A change amount of a fuel level in a fuel tank is checked for whether or not it is a preset value or more (S1) based on a signal from a fuel level sensor, in the case that the change amount of the fuel level is the preset value or more, a change amount of a fuel temperature based on an output of a fuel temperature sensor is checked for whether or not it is a diagnostic decision value or more (S2). As a result, in the case of the change amount of the fuel temperature not reaching the diagnostic decision value, an NG counter CNG is applied with an increment (S5), the NG counter CNG is checked for whether or not obtaining a preset number of times or more (S6). In the case of the NG counter CNG obtaining the preset number of times, the fuel temperature sensor is decided to be in trouble (S7). In this way, a condition changing the fuel temperature is surely caught to prevent the erroneous decision, reliability of diagnosis is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for diagnosing failure of a fuel temperature sensor for detecting the temperature of fuel in a fuel tank.

[0002]

2. Description of the Related Art In general, in a vehicle such as an automobile using an engine as a driving power source, various technologies for controlling an engine are employed to prevent air pollution and conserve resources. The evaporative fuel gas generated inside the canister is adsorbed on activated carbon or the like in the canister and temporarily stored so that the evaporative gas of the fuel generated in the canister is not discharged to the atmosphere. There is a so-called evaporative purge device for inhaling air into the combustion chamber of the engine.

Conventionally, the failure diagnosis of the evaporative purge device has been performed by detecting a change in fuel pressure. In recent years, however, the temperature of fuel in a fuel tank has been measured to estimate the amount of evaporative gas generated. Techniques for performing various diagnoses have been adopted. For this reason, if an abnormality occurs in the sensor itself that detects the fuel temperature, the reliability of the failure diagnosis of the evaporative purge device decreases, so that the failure diagnosis of the fuel temperature sensor is required.

Conventionally, as a failure diagnosis of a temperature sensor, there is a failure diagnosis technique of an engine temperature sensor disclosed in Japanese Patent Application Laid-Open No. H11-351976.
If the degree of change of the temperature sensor output is within a predetermined degree,
It is determined that the temperature sensor is abnormal.

[0005]

However, usually,
Since the temperature change of the fuel temperature is smaller than the engine temperature disclosed in the prior art, an erroneous determination occurs only by monitoring the output change of the fuel temperature sensor and diagnosing the abnormality.

The present invention has been made in view of the above circumstances, and when diagnosing an abnormality of a fuel temperature sensor for detecting the temperature of the fuel in a fuel tank, an erroneous determination is made by reliably detecting a state in which the fuel temperature changes. An object of the present invention is to provide a failure diagnosis device for a fuel temperature sensor that can prevent the failure and improve the reliability of diagnosis.

[0007]

In order to achieve the above object, the invention according to claim 1 is a fuel temperature sensor failure diagnostic apparatus for diagnosing abnormality of a fuel temperature sensor for detecting the temperature of fuel in a fuel tank. A fuel level sensor for detecting a level of fuel in the fuel tank; and a change in fuel level detected by the fuel level sensor being equal to or greater than a set value, and a fuel temperature detected by the fuel temperature sensor. An abnormality determining unit that determines that the fuel temperature sensor is abnormal when the amount of change is equal to or less than the diagnosis determination value.

According to a second aspect of the present invention, in the first aspect of the present invention, the abnormality determining means includes a fuel level change amount detected by the fuel level sensor that is equal to or greater than the set value and the fuel temperature sensor Count the number of times the amount of change in the fuel temperature detected by is less than or equal to the diagnostic determination value,
When the count value exceeds a set number, the fuel temperature sensor is determined to be abnormal.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the set value can be determined to be based on the fact that a change in the fuel level in the fuel tank is caused by refueling the fuel tank. Value.

According to a fourth aspect of the present invention, there is provided a failure diagnosis device for a fuel temperature sensor for diagnosing abnormality of a fuel temperature sensor for detecting a temperature of fuel in a fuel tank, wherein the level of the fuel in the fuel tank is detected. A fuel level sensor, an intake air amount detecting means for directly or estimating an intake air amount of the engine, and a fuel temperature change amount detected by the fuel temperature sensor being equal to or less than a diagnosis determination value, and An abnormality determining unit that determines that the fuel temperature sensor is abnormal when the integrated value of the intake air amount detected by the amount detecting unit is equal to or greater than a set value.

A fifth aspect of the present invention is characterized in that, in the fourth aspect of the invention, the set value is a value equal to or greater than the integrated value of the intake air amount proportional to the capacity of the fuel tank.

That is, according to the first aspect of the present invention, the fuel level in the fuel tank is detected, and the detected fuel level change is equal to or more than a set value, and the fuel temperature change detected by the fuel temperature sensor. When the amount is equal to or less than the diagnosis determination value, the fuel temperature sensor determines that the fuel temperature is abnormal, so that a state in which the fuel temperature changes is reliably detected to prevent erroneous determination and improve the reliability of diagnosis. At this time, the invention according to claim 2 counts the number of times that the amount of change in the fuel level is equal to or more than the set value and the amount of change in the detected fuel temperature is equal to or less than the diagnosis determination value, and the counted value indicates the set number of times. If it exceeds, the reliability of diagnosis is further improved by determining that the fuel temperature sensor is abnormal. Further, according to the third aspect of the present invention, by setting the set value to a value that can determine that the change in the fuel level in the fuel tank is due to the refueling of the fuel tank, the set value can be set when the fuel temperature changes greatly. Diagnosis.

According to a fourth aspect of the present invention, the amount of change in the fuel temperature detected by the fuel temperature sensor is equal to or less than the diagnostic determination value, and the integrated value of the intake air amount detected by the intake air amount detecting means is set. When the value is equal to or larger than the value, the fuel temperature sensor is determined to be abnormal, so that a state in which the fuel temperature changes is reliably detected, erroneous determination is prevented, and the reliability of diagnosis is improved. In this case, the invention according to claim 5 makes it possible to make a diagnosis at the time of refueling with a large change in fuel temperature 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]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 5 show 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,
3 is a time chart of a refueling diagnosis, FIG. 4 is a time chart of a traveling diagnosis (OK determination), and FIG. 5 is a traveling diagnosis (N
6 is a time chart of (G determination).

In FIG. 1, reference numeral 1 denotes an engine,
A throttle valve 3 is interposed in an intake pipe 2 of the engine 1, and an air flow sensor (intake air amount sensor) 4 of a hot wire type or a hot film type is disposed upstream of the throttle valve 3. An injector 5 is disposed downstream of the throttle valve 3. The injector 5 is pressure-fed from a fuel pump 7 disposed in a fuel tank 6 and adjusted to a predetermined pressure by a pressure regulator 8. Pressurized fuel is supplied.

The fuel tank 6 is provided with a float type fuel level sensor 9 for detecting the fuel level in the tank. In order to detect the temperature of the fuel, a fuel temperature sensor 10 is attached. Air flow sensor 4, fuel level sensor 9, and fuel temperature sensor 10
Is an electronic control unit (E
The ECU 20 is connected to the ECU 20 and diagnoses abnormality of the fuel temperature sensor 10 by a diagnostic function of the ECU 20. When an abnormality occurs, an alarm signal is output from the ECU 20 to the alarm device 21 to issue an alarm.

Hereinafter, the fuel temperature sensor 1 by the ECU 20 will be described.
The diagnostic processing of 0 will be described with reference to the flowchart of FIG. Note that an initial diagnosis is performed on the fuel temperature sensor 10 when the ignition switch is turned on. In the initial diagnosis, an abnormality determination counter (NG counter) CNG described below is set once, and when the output of the fuel temperature sensor 10 exceeds a predetermined value, it is determined that the fuel temperature sensor 10 is normal and the NG counter CNG is cleared. Then, after the operation of the system, the fuel temperature sensor diagnosis routine of FIG. 2 is executed at predetermined time intervals.

In the fuel temperature sensor diagnosis routine, first,
In step S1, it is checked based on a signal from the fuel level sensor 9 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. This condition is a condition for diagnosing the fuel temperature sensor 10 by reliably grasping a state in which the fuel temperature changes. When the vehicle is running, the fuel level in the fuel tank 6 is reduced in response to a decrease in the fuel level due to fuel consumption. The temperature rises due to agitation (circulation) by the fuel pump 7, heat reception around the engine, and the like, and decreases when new fuel is supplied by refueling. Therefore, the fuel tank 6
Diagnosis by detecting changes in the fuel level inside
An abnormality of the fuel temperature sensor 10 can be reliably detected.

In this case, the set value for examining the diagnostic conditions may be a value corresponding to one of the time of running and the time of refueling. Prior to execution, determine when to run and when to refuel,
It is desirable to select a value corresponding to the time of traveling and a value corresponding to the time of refueling and set the value to a set value. For example, a change rate per unit time of the fuel level is determined to determine whether the vehicle is running or refueling, and a value capable of determining that the change in the fuel level in the fuel tank 6 is due to refueling of the fuel tank 6. ,
A value that can be determined to be due to fuel consumption during traveling is selected and set in advance to a set value. 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, the fuel efficiency of the vehicle, and the like.
Engine displacement and type, fuel consumption, engine load, vehicle speed,
It is set in consideration of the shift position and the like.

If it is determined in step S1 that the amount of change in the fuel level has not reached the set value, the process directly exits the routine. If the amount of change in the fuel level is equal to or more than the set value, the process proceeds to step S2, It is checked whether or not the amount of change in the fuel temperature based on the output of the sensor 10 is equal to or greater than the diagnosis determination value. That is, a fuel temperature change width corresponding to a decrease in fuel during traveling or an increase in fuel due to refueling is determined in advance, and a margin is added to this temperature change width to make a diagnosis determination value. Then, the diagnosis determination value and the actual fuel temperature sensor 1
By comparing the amount of change in the fuel temperature measured by 0 with the fuel temperature sensor 10, it is determined whether the fuel temperature sensor 10 is normal.

As a result, if the amount of change in the fuel temperature measured by the fuel temperature sensor 10 is equal to or larger than the diagnosis determination value, the process proceeds from step S2 to step S3, where the NG counter CNG is cleared (CNG ← 0). In S4, it is determined that the fuel temperature sensor 10 is normal (OK determination), and the routine exits. If the amount of change in the fuel temperature measured by the fuel temperature sensor 10 has not reached the diagnosis determination value, the fuel temperature sensor 10 may be abnormal, and the process proceeds from step S2 to step S5 and proceeds to the NG counter. 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.

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 has exceeded the set number of times, the fuel temperature sensor 10 is determined in step S7. Is determined to be a failure, an NG determination is made, and an alarm is issued via the alarm 21 to exit the routine. That is, when the fuel temperature change is small with respect to the decrease in the fuel level due to the fuel consumption during traveling, or when the fuel temperature during refueling is substantially equal to the temperature of the fuel in the fuel tank 6, the fuel in the fuel tank 6 is refueled. In some cases, the temperature of the fuel temperature sensor 10 does not change so much. Therefore, when the NG determination is made a plurality of times, the fuel temperature sensor 10 is determined to be faulty for the first time, thereby ensuring the reliability of diagnosis and avoiding erroneous determination.

FIG. 3 is a time chart in the case of diagnosing the fuel temperature sensor 10 by catching a change in fuel level caused by refueling. The fuel temperature rises in response to a decrease in fuel level, and new fuel is supplied by refueling. Then, the fuel temperature in the fuel tank 6 decreases. Therefore, if the fuel temperature measured by the fuel temperature sensor 10 changes in accordance with the change in the fuel level, it is determined that the fuel temperature sensor 10 is normal and the OK determination is made. In the normal case, the set / clear of the NG counter CNG is repeated. On the other hand, the fuel temperature sensor 10
If the fuel temperature measured 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, the fuel temperature sensor 10 is determined to be faulty and an NG determination is made.

FIGS. 4 and 5 are time charts in a case where the fuel temperature sensor 10 is diagnosed by detecting a change in the fuel level during traveling. As shown in FIG. When the fuel temperature measured by the fuel temperature sensor 10 gradually increases in response to this, the fuel temperature sensor 10 determines that it is normal and makes an OK determination, and clears the NG counter CNG. On the other hand, as shown in FIG. 5, even if the decrease in the fuel level reaches the set value, the output of the fuel temperature sensor 10 is stuck (stuck).
If the measured value of the fuel temperature does not change, for example,
When the G counter CNG is incremented and reaches the set number of times, it is determined that the fuel temperature sensor 10 has failed and N
A G determination is made.

That is, instead of simply monitoring the output change of the fuel temperature sensor 10 to diagnose 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. Therefore, an abnormality can be reliably detected without causing an erroneous determination, and the quality of diagnosis can be improved.

6 and 7 relate to a 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.

The second embodiment is different from the first embodiment in that the engine 1 has a parameter corresponding to the amount of change in the fuel level.
Is used. That is,
A decrease in the fuel level in the fuel tank 6 (a decrease in fuel) due to fuel consumption during traveling can be grasped from the intake air amount proportional to the fuel consumption. Therefore, when the ignition switch is turned 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.

For this reason, in the fuel temperature sensor diagnosis routine of the second embodiment shown in FIG. 6, first, in step S10, it is checked whether or not the amount of change in the fuel temperature measured by the fuel temperature sensor 10 is equal to or larger than a diagnosis determination value. The diagnosis determination value here is a value in which a change width of the fuel temperature corresponding to a change in the fuel amount corresponding to the set value in the following step S11 is obtained in advance, and a slight margin is added to the temperature change width.

If the amount of change in the fuel temperature has not reached the diagnosis determination value, the flow proceeds from step S10 to step S10.
Proceeding to 12, it is checked whether or not the integrated value of the intake air amount measured by the air flow sensor 4 has become equal to or greater than a set value. This set value is an integrated value of the intake air amount corresponding to the fuel change amount at which the fuel temperature change can be reliably detected. 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, a change in fuel temperature due to refueling can be grasped.

As a result, if the integrated value of the intake air amount has not reached the set value, the process returns to step S10 to continue the process. Thereafter, when the amount of change in 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 is determined. Clear the integrated value and exit the routine. On the other hand, if the integrated value of the intake air amount becomes equal to or larger than the set value in step S11 while the amount of change in the fuel temperature does not reach the diagnosis determination value in step S1, it is determined that the fuel temperature sensor 10 is abnormal.
Proceeding to 13, the NG determination is made (see FIG. 7 (b)), and an alarm is issued via the alarm 21 to exit the routine.

In the second embodiment, similarly to the first embodiment, it is possible not only to diagnose the abnormality of the fuel temperature sensor 10 without causing an erroneous determination, but also to be affected by the constantly changing load and operating condition. Without this, stable diagnosis can be performed.

In the second embodiment, the amount of intake air is directly detected by the air flow sensor 4. However, the present invention is not limited to this. For example, based on the engine speed and the throttle opening, the amount of intake air may be reduced. The intake air amount may be estimated based on the fuel injection width (amount) and the throttle opening.

[0033]

As described above, according to the present invention, when diagnosing an abnormality of the fuel temperature sensor for detecting the temperature of the fuel in the fuel tank, a state in which the fuel temperature changes is surely grasped to make an erroneous determination. Prevention and the reliability of diagnosis can be improved.

[Brief description of the drawings]

FIG. 1 is an explanatory view 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 diagnosis routine according to the first embodiment;

FIG. 3 is a time chart of a refueling diagnosis.

FIG. 4 is a time chart of a traveling diagnosis (OK determination);

FIG. 5 is a time chart of a traveling diagnosis (NG determination);

FIG. 6 is a flowchart of a fuel temperature sensor diagnosis routine according to the second embodiment of the present invention;

FIG. 7 is a time chart of a diagnosis according to the first embodiment;

[Explanation of symbols]

 6 Fuel tank 9 Fuel level sensor 10 Fuel temperature sensor 20 ECU

Claims (5)

[Claims] 1. A failure diagnosis device for a fuel temperature sensor for diagnosing an abnormality of a fuel temperature sensor for detecting a temperature of fuel in a fuel tank, comprising: a fuel level sensor for detecting a level of fuel in the fuel tank; When the amount of change in the fuel level detected by the fuel level sensor is equal to or more than a set value, and the amount of change in the fuel temperature detected by the fuel temperature sensor is equal to or less than a diagnosis determination value,
An abnormality determining means for determining that the fuel temperature sensor is abnormal; a failure diagnostic device for the fuel temperature sensor. 2. The abnormality determination means according to claim 1, wherein a change amount of the fuel level detected by the fuel level sensor is equal to or more than the set value, and a change amount of the fuel temperature detected by the fuel temperature sensor is determined by the diagnosis determination value. 2. The failure diagnosis device for a fuel temperature sensor according to claim 1, wherein the following number is counted, and when the counted value exceeds a set number, the fuel temperature sensor is determined to be abnormal. 3. The fuel cell system according to claim 1, wherein the set value is a value capable of determining that a change in the fuel level in the fuel tank is due to refueling of the fuel tank.
Or a failure diagnosis device for a fuel temperature sensor according to 2. 4. A failure diagnosis device for a fuel temperature sensor for diagnosing an abnormality of a fuel temperature sensor for detecting a temperature of fuel in a fuel tank, comprising: a fuel level sensor for detecting a level of fuel in the fuel tank; An intake air amount detecting means for detecting the amount of intake air directly or by estimation; and a change amount of the fuel temperature detected by the fuel temperature sensor being equal to or less than a diagnosis determination value and being detected by the intake air amount detecting means. An abnormality determining means for determining that the fuel temperature sensor is abnormal when the integrated value of the intake air amount is equal to or greater than a set value. 5. The failure diagnosis device for a fuel temperature sensor according to claim 4, wherein said set value is a value equal to or greater than an integrated value of an intake air amount proportional to a capacity of said fuel tank.