FR3072778B1 - METHOD FOR DIAGNOSING A WATER PRESENCE SENSOR IN A VEHICLE FUEL CIRCUIT - Google Patents

Abstract

A method of diagnosing a water presence sensor in a vehicle fuel circuit, said sensor being configured to transmit a diagnostic signal after it has been powered up, said method comprising the following steps: • power-up of the sensor , • measuring a stopping time (t0-t1) of the power supply of the sensor before said powering up, and, only if said measured stopping time (t0-t1) is greater than a time threshold predetermined: • measurement during a time window (t2-t5) of the transmission duration (t3-t4) of the diagnostic signal, and • generation of a sensor malfunction alert if the emission duration (t3-t4 ) of the measured diagnostic signal is less than a minimum duration during the time window (t2-t5).

Description

METHOD FOR DIAGNOSING A WATER PRESENCE SENSOR IN A VEHICLE FUEL CIRCUIT

The present invention relates generally to a method of diagnosing a water presence sensor in a fuel circuit mounted on a motor vehicle. In addition, the present invention relates to an engine operating method including a diagnostic method and a device for detecting water in a fuel system implementing these methods.

[0002] Certain vehicles, in particular those intended for markets in which the quality of the fuel may be low, and in particular diesel fuel also known as diesel fuel, are provided with a sensor for the presence of water in the fuel, in order to identify fuels unsuitable for use because of a too high water content and thus prevent engine failures and malfunctions by preventing the consumption of such fuels.

It is known to the applicant a diagnostic method of a water presence sensor in a vehicle fuel system. In such a method, the sensor is configured to transmit a diagnostic signal after it is powered up and the duration of this signal is measured during a time window or diagnostic window. If the duration of this diagnostic signal is less than a minimum duration, an alert is then generated to inform a user of the vehicle that the sensor of presence of water in the fuel is defective.

However, depending on the type of sensor, it is possible that false alarms are generated, that is to say that an alert can be generated while the sensor of presence of water in the fuel n ' is not defective.

An object of the present invention is to address this drawback and in particular to provide a method of diagnosing a water presence sensor in a vehicle fuel system reducing the risk of emitting a false alarm .

For this, a first aspect of the invention relates to a method for diagnosing a water presence sensor in a vehicle fuel circuit, for example diesel fuel, said sensor being configured to emit a diagnostic signal. after it is powered up, said method comprising the following steps: • energizing the sensor, • measuring a power-off time of the sensor before said power-on, and, only if said time of measured stop is greater than a predetermined time threshold: • measurement during a time window of the duration of transmission of the diagnostic signal, and • generation of a sensor malfunction alert if the duration of transmission of the diagnostic signal measured is less than a minimum duration during the time window.

In other words, the diagnostic process executes the diagnostic steps only in the case where the power supply of the sensor has been stopped or cut off long enough. This makes it possible to avoid any phenomenon of supply or of residual polarization, or of absence of complete discharge of the sensor which can lead to an erroneous diagnosis, that is to say, to remission of a false alarm of malfunction of the sensor. presence of water even though this sensor is functional.

[0008] Advantageously, said diagnostic signal is a signal obtained by grounding an output of the sensor. In addition, the signal normally emitted by the sensor, corresponding for example to a suitable fuel without water may be a voltage, such as a voltage of 12 V, which simplifies the design of the water detection device according to the present invention. invention.

In other words, the sensor has an output that is energized when the sensor is operating and the diagnostic signal can be a zero of this voltage, that is to say a grounding.

Advantageously, the duration of transmission of the diagnostic signal is calculated as being a difference between the duration of the time window and a duration during which the sensor emits a signal different from a signal obtained by grounding the signal. an output of the sensor, for example a voltage of 12 V. This makes it possible to further simplify the diagnostic process as well as the design of the device for detecting water in the fuel while avoiding most false alarms, that is, ie most inappropriate alarms of water presence sensor malfunction.

For example, the predetermined time threshold is 1 to 5 seconds (s).

In addition, the theoretical or expected transmission time of the diagnostic signal is for example 500 milliseconds (msec) to 1.5 seconds (s) and the minimum duration is for example 300 milliseconds (msec).

A second aspect of the invention is an engine operating method comprising: a method for diagnosing a water presence sensor in a fuel circuit according to the first aspect of the invention; a verification method; presence of water in a fuel circuit of a vehicle, wherein said water presence sensor is configured to emit a water presence signal.

Advantageously, said water presence signal is a grounding and the normal signal emitted by the sensor, for example corresponding to a suitable fuel without water may be a voltage, for example a voltage of 12 V .

A third aspect of the present invention is a device for detecting water in a fuel circuit for a vehicle, said device comprising: a sensor configured to emit a determined signal in the event of presence of water in the circuit and to transmit said signal upon power-up; a computer configured to perform the method according to any of the preceding aspects of the present invention.

A final aspect of the invention is a vehicle comprising at least one device according to the third aspect of the invention or implementing at least one method according to any one of the first and second aspects of the invention.

Other features and advantages of the present invention will appear more clearly on reading the following detailed description of an embodiment of the invention given by way of non-limiting example and illustrated by the accompanying drawings, in which: Figure 1 shows a flowchart of a diagnostic method according to the present invention. FIG. 2 represents a sequential diagram of the diagnostic method according to FIG. 1; FIG. 3 represents an example of the electrical connection of a water presence sensor and an engine management computer implementing the diagnostic method according to FIG. figure 1.

The diagnostic method according to the present invention is used for any type of vehicle using fuel, including private vehicles, commercial or commercial, construction equipment, collective vehicles, military vehicles or boats.

In addition, this diagnostic method is performed by a vehicle computer, for example an engine management computer, which is connected to at least one sensor of presence of water in the fuel. This sensor is for example located in the vehicle fuel system, for example at the fuel tank of the vehicle or the fuel filter. It is a sensor according to the state of the art, for example measuring a conduction of electricity in the fuel and thus returning a voltage, for example 12 V, in the absence of water and a lack of voltage or 0 V in the case of electrical conduction achieved by the presence of water in the fuel. Alternatively, it may be a sensor placed in the fuel tank and having a float floated only by water and not by fuel; a signal is then generated if the float exceeds a certain level. In all cases, the sensor is programmed or configured to issue a diagnostic signal after a certain period of time after it is turned on.

FIG. 1 represents a flowchart of a diagnostic method according to the present invention and FIG. 2 represents a time diagram of this diagnostic method. Time diagram 2-1 shows the variation over time of the supply voltage of the water presence sensor. Time diagram 2-2 represents the variation over time of a signal emitted by the water presence sensor and serving at least a diagnostic signal and possibly a signal of presence of water in the fuel. Finally, the timing diagram 2-3 represents a time window or diagnostic window during which the engine management computer records the variations of the signal emitted by the water presence sensor.

With reference to these two figures and particularly to Figure 2, a driver or a user cuts the vehicle contact, which leads to a power failure of the computer to tO and ceases any power supply of the presence sensor of water. In a first step (step A -figure 1), t1 a driver or a user of the vehicle puts the vehicle in contact in order to start his engine. The engine management computer is then powered again, a power relay is triggered and provides a power supply to the water sensor in the fuel at time t1. A voltage of 12 V is therefore detected by the engine management computer.

In a second step or step B, the engine management calculator calculates the stopping time since the last power on of the sensor, the duration (tO-t1) in FIG. 2. Thus, if the sensor is fed directly by the engine management computer, it is the time during which the engine management computer has remained unpowered, that is to say between the moment when the power supply of the computer has been cut (as a result the driver's contact break) and the moment when a driver switched on the vehicle. However, a time shift can exist between the moment when the engine management computer is electrically powered and the moment when the water presence sensor is electrically powered, because of the tripping time of a power relay supplying the power supply. water presence sensor.

The stopping time (tO-t1) can be measured by means of a dedicated counter within the engine management computer or be measured by another computer of the vehicle. Thus, a clock can be triggered at the time of stopping the power of the computer and stopped at the time of handing the vehicle contact, or, alternatively, the time data including the dates and times of stopping the power supply. the computer and the delivery of the contact can be stored in a memory of a computer.

In a third step or step C, the stopping time (t0-t1) measured in the previous step is compared with a predetermined time threshold (t-threshold). If the stopping time (tO-t1) is greater than the predetermined time threshold (t-threshold), that is (tO-t1)> (t-threshold), then the diagnostic process is continued as described below in reference to steps D to F. In the opposite case, that is to say if the stopping time (tO-t1) is less than the predetermined threshold time (t-threshold), ie (tO-t1) < (t-threshold), then the diagnostic process is not executed and / or the diagnostic signal of the sensor is ignored. The predetermined time threshold (t-threshold) can be obtained by calibration of the sensor and can be from 1 to 5 seconds, for example.

In the case where the diagnostic method is executed, that is to say in the case where it has been determined that the stopping time (tO-t1) is greater than the predetermined threshold time (t- threshold), the engine management computer is placed in reception mode and opens a time window (t2-t5) to receive a diagnostic signal from the sensor. This time window can be opened for example after a duration (t1-t2) of 200 ms. The engine management computer then measures, in a step D, the transmission duration of this diagnostic signal, ie the duration (t3-t4) in FIG. 2. In the present embodiment, the diagnostic signal is similar to a water signal in the fuel and materialized by a passage of current or a ground, resulting in a voltage of 0 V at the terminals of the engine management computer. However, different signals may be used for the diagnostic signal and the water presence signal.

In a fifth step or step E, the transmission duration of the diagnostic signal (t3-t4) measured in step D is compared with a minimum duration (d-minimum). This comparison step E can be performed by the engine management computer, but can also be performed by another computer. If the transmission time (t3-t4) of the diagnostic signal is greater than the minimum duration, ie (t3-t4)> (d-minimum), then the sensor is functional and the engine management computer switches to checking for the presence of water. In the opposite case, that is, if the transmission duration (t3-t4) is less than the minimum duration (d-minimum), that is (t3-t4) <(d-minimal), then the The sensor is considered to be defective and a sensor malfunction alert is issued by the engine management computer to a user or driver of the vehicle.

For example, an indicator can light on the dashboard of the vehicle and / or an error message can be displayed on a vehicle screen. In addition, depending on the country and the setting made by the manufacturer or the importer of the vehicle, the engine management computer generating the sensor malfunction alert can prevent a starting of the engine of the vehicle, so as to prevent any risk of malfunction or engine damage associated with the use of a fuel containing water.

For example, the minimum duration is predetermined according to a calibration and / or according to the specifications of the water presence sensor, for example to a value of 300 ms. In addition, the duration of transmission of the diagnostic signal can be expected (that is to say, theoretical value) from 500 msec to 1500 msec, or 1 s +/- 0.5s.

Moreover, in the case where the comparison made in step C shows that the stopping time (tO-t1) is less than the predetermined threshold time (t-threshold), ie (tO-t1) <(t-threshold), the sensor can be further polarized, current recirculation may exist or the sensor may not be fully discharged electrically so there is a significant risk of misdiagnosis during the present diagnostic process of the water presence sensor. In other words, there is a risk of incorrectly determining that the water sensor in the fuel is defective on the basis of a too short transmission of a diagnostic signal by the sensor, resulting in a comparison (t3-t4 ) <(d-minimum) in step E of the present diagnostic method, even though the sensor of presence of water in the fuel is fully functional.

In this case, the present method ignores steps D to F described above and / or ignores any diagnostic signal issued by the water presence sensor. The computer then goes into water presence checking mode, for example at the end of a predetermined time. In other words, if the stop time of the supply of the water presence sensor is too short, the diagnostic process does not perform the diagnostic steps D to F, or at least not the step F, but only executes the process of checking the presence of water.

In the water presence verification mode, the engine management computer executes a method for checking the presence of water in the fuel according to the state of the art, consisting for example of triggering an alert when the signal corresponding to the presence of water in the fuel is emitted for a significant time by the sensor of presence of water in the fuel. This water presence signal is preferably the same as the diagnostic signal but may be different depending on the type of water presence sensor.

Finally, Figure 3 shows a schematic view of the electrical assembly of the water presence sensor 10 to the engine management computer 20. Thus, the water presence sensor 10 comprises an output terminal 11, a mass 12 and a power supply 13, for example 12 V. The engine management computer 20 comprises an input terminal 21 electrically connected to the output terminal 11 of the sensor, a ground 22, a bias voltage of the sensor signal (for example 12V or 5V) 23 and a bias resistor 24 of the input terminal 21 or "pull-up". The computer thus measures a signal between the input terminal 21 and the ground 22. The sensor 10 is immersed in the fuel and, in the absence of water, a voltage of 12V is measured at the input terminal 21 of the computer. On the other hand, when water is present, the sensor 10 switches the output terminal 11 on the ground 10, thus setting the input terminal 21 to ground, which corresponds to a zero voltage and to a diagnostic signal and / or water presence.

It will be understood that various modifications and / or improvements obvious to those skilled in the art can be made to the various embodiments of the invention described in the present description without departing from the scope of the invention. In particular, reference is made to the type of water presence sensor and the type of calculator, which are not limited to the above examples. In addition, the duration of transmission of the diagnostic signal (t3-t4) can be measured directly or by subtraction of the time window (t2-t5) with the durations (t2-t3) and (t4-t5) during which the signal emitted by the water presence sensor is at a voltage of 12 V.

Claims (9)

A method of diagnosing a sensor (10) for the presence of water in a vehicle fuel circuit, said sensor (10) being configured to transmit a diagnostic signal after it has been powered up, said method comprising the following steps : • energizing the sensor (step A), • measuring a dwell time (tO-t1) of the sensor power supply (10) before said power-on (step B), and only if said measured stopping time (t0-t1) is greater than a predetermined time threshold (t-threshold) (step C): • measuring during a time window (t2-t5) of the transmission duration (t3- t4) of the diagnostic signal (step D), and • generation of a sensor malfunction alert (step F) if the transmission duration (t3-t4) of the measured diagnostic signal is less than a minimum duration (d). -minimal) during the time window (t2-t5) (step E). 2. Diagnostic method according to the preceding claim, wherein said diagnostic signal is a signal obtained by grounding an output (11) of the sensor (10). Diagnostic method according to any one of the preceding claims, wherein the transmission duration (t3-t4) of the diagnostic signal is calculated as being a difference between the duration of the time window (t2-t5) and a duration during which the sensor emits a signal different from a signal obtained by grounding a sensor output (t2-t3; t4-t5). 4. Diagnostic method according to one of the preceding claims, wherein the predetermined time threshold (t-threshold) is from 1 to 5 seconds (s). 5. Diagnostic method according to one of the preceding claims, wherein the minimum duration (d-minimum) is 300 milliseconds (msec). An engine operating method comprising: a method of diagnosing a sensor (10) for the presence of water in a fuel system according to any one of the preceding claims; a method for checking the presence of water in a fuel system of a vehicle, wherein said water presence sensor (10) is configured to emit a water presence signal. 7. Engine operating method according to the preceding claim wherein said water presence signal is a grounding. 8. Device for detecting water in a fuel circuit for a vehicle, said device comprising: a sensor (10) configured to emit a determined signal in the event of presence of water in the fuel circuit and to emit said signal upon power-up • a computer (20) configured to implement the method of any one of the preceding claims. 9. Vehicle comprising at least one device according to the preceding claim.