DE102014218816B4 - Method and device for detecting a leak of a tank of a vehicle and computer program product - Google Patents

Abstract

Method for detecting a leak of a tank (3) of a vehicle (1), in which in a first step (S1) between a start (T2) and an end time (T4) of a predetermined time window (Tf) at least two measured values (M1, M2 ) of a tank temperature (T), on the basis of which a cumulative rise (D +) and a fall (D) of the tank temperature (T) are determined, in which case a predetermined first threshold (Dmax) is determined by the cumulative increase (D + ), and / or the decrease (D-) at the end time (T4) is less than a predetermined second threshold (Dmin), the beginning (T2) of the predetermined time window (Tf) is shifted in time, and the first step (S1 ) is performed repeatedly, and otherwise in a second step (S2) from a period of time (T3) in a predetermined period of time (Tc), a state of a characteristic (S) is determined, which is representative of the leak of the tank (3).

Description

The invention relates to a method for detecting a leak of a tank of a vehicle. Furthermore, the invention relates to a device for detecting a leak of a tank of a vehicle. Furthermore, the invention relates to a computer program product.

Usually, a fuel tank of a vehicle with an internal combustion engine is sealed in such a way that escape of fuel vapor is avoided. A drop in the temperature of the fuel tank leads to the formation of a vacuum in the case of an intact fuel tank, which can be detected. On the other hand, if there is a leak in the fuel tank, fuel vapor may escape into the atmosphere, which contributes to emission of the vehicle.

The publication US 6,321,727 B1 describes a method for detecting a leak in a tank of a vehicle in which a drain valve and a vent valve are closed after the engine is turned off and a fuel vapor temperature and a tank pressure are measured during a period in which the engine is turned off and the fuel vapor temperature decreases. The pressure and the temperature are recorded in the time span and the vent valve is then opened. An indication is provided for an undetectable system leak if the pressure drops below atmospheric pressure, or an indication of a system leak is taken if the pressure does not drop below atmospheric pressure during the time period.

The publication US 2001/0032626 A1 describes a method for detecting a leak in a tank of a vehicle in which an engine is turned off and a starting temperature and a starting pressure are determined. A rating temperature is provided and a temperature difference between the start temperature and the rating temperature is calculated. A time counter is incremented when the temperature difference is greater than a temperature control value. A pressure difference is detected between the start pressure and a judgment pressure, and the time counter is compared with a time control value when the pressure difference is not greater than a pressure control value.

The publication US 2011/0295482 A1 describes a method of operating a fuel vapor equalization system in which a first amount of fuel vapor is discharged from a canister into an engine intake during a bleed condition. After draining the first amount, a second amount of fuel vapor is drained from the canister into the engine intake, wherein the second amount is adjusted based on the first amount.

An object underlying the invention is to provide a method and a corresponding device that contributes to a reliable detection of a leak of a tank of a vehicle and at the same time can be implemented in a cost-effective and space-saving manner.

The object is solved by the features of the independent claims. Advantageous developments of the invention are characterized in the subclaims.

According to a first aspect, the invention is characterized by a method for detecting a leak of a tank of a vehicle, wherein in a first step between a start and an end time of a predetermined time window at least two measured values of a tank temperature are determined. Depending on the at least two measured values, a cumulative increase in the tank temperature and a fall in the tank temperature in the given time window are determined.

In particular, a plurality of measured values is determined in the predetermined time window for this purpose.

In the event that a predetermined first threshold is exceeded by a cumulative increase, a corresponding first time is determined, to which the beginning of the predetermined time window is shifted in time and the first step is performed repeatedly.

Alternatively and / or additionally, in the event that the decrease at the end time is less than a predetermined second threshold, the beginning of the predetermined time window is shifted in time to the end time and the first step is repeatedly performed.

In the event that the fall in the tank temperature exceeds the predetermined second threshold value, in a second step, starting from a time span at which the waste exceeds the predetermined second threshold, a state of a characteristic value representative of the leak is determined within a predetermined period of time of the tank.

In the event that the predetermined first threshold value is exceeded after the start of the period by the cumulative increase, the corresponding first time is determined, to which the beginning of the predetermined time window in time is moved and the first step is performed repeatedly.

Alternatively and / or additionally, in the event that the drop falls below the predetermined second threshold value after the beginning of the period of time, a corresponding second instant is determined, to which the beginning of the predetermined time window is shifted in time and the first step is carried out repeatedly.

Determining the at least two measured values only in the predetermined time window has the advantage that only a limited number of data has to be processed. Because of this results in a low power requirement of a device for performing the method, so that it can be produced inexpensively and compactly. A displacement of the predetermined time window also allows, while maintaining these advantages, a reliable detection of a leak of the tank even for a period of time which is longer than the predetermined time window.

Further, by determining the accumulated increase in the tank temperature, a temperature fluctuation within the predetermined time window is taken into account, so that it is possible to detect a leakage of the tank with high reliability.

For example, in this case, a signal of a vacuum pressure switch is evaluated to determine the characteristic value. In the event that due to the drop in the tank temperature, a vacuum would have to arise in a sealed system, but the signal of the vacuum pressure switch in the predetermined period of time remains unchanged, it can be assumed that there is a leak in the tank.

The drop in the tank temperature in the given time window is calculated, for example, as the amount of a difference of a first measured value of the at least two measured values at the beginning of the predefined time window and a second measured value of the at least two measured values at a current time.

The accumulated increase in the tank temperature corresponds, for example, to a summation of a respective difference of a preceding minute of the at least two measured values and a subsequent thereto subtrahend of the at least two measured values, which assumes a positive value between the beginning of the predetermined time window and the current time.

The first time corresponds to an exceeding of the predetermined first threshold value by the cumulative increase. The second time corresponds to an occurrence of falling below the predetermined second threshold by the waste. The start of the period corresponds to an occurrence of exceeding the predetermined second threshold by the waste.

In an advantageous embodiment according to the first aspect, an engine-off time is determined, to which an engine of the vehicle is set in an off state. The first step is then carried out after a predetermined waiting time after the engine-off time. The default waiting time is between 1 minute and 180 minutes. In particular, the predetermined waiting time is 90 minutes.

This contributes to avoiding a period of detection of a leak of the tank in which a variation of the tank temperature is subject to a possible fluctuation. For example, this makes it possible to detect a leak of the tank with high reliability. Advantageously, this contributes to a low power requirement for a device for carrying out the method. For example, the apparatus for performing the method for the predetermined waiting time can switch to a power saving mode.

In a further advantageous embodiment according to the first aspect, the predetermined first threshold is between 0.1 ° C and 5 ° C. In particular, the predetermined first threshold value is between 1 ° C and 2 ° C, in particular 1.5 ° C.

This has the advantage that, in particular, the size and / or the geometry and / or the arrangement of the tank is taken into account, so that a detection of a leak of the tank with high reliability is contributed.

In a further advantageous embodiment according to the first aspect, the predetermined second threshold is between 3 ° C and 10 ° C. In particular, the predetermined second threshold value is between 5 ° C and 8 ° C, in particular 6 ° C.

This has the advantage that, in particular, the size and / or the geometry and / or the arrangement of the tank is taken into account, so that a detection of a leak of the tank with high reliability is contributed.

In a further advantageous embodiment according to the first aspect, an indicator signal is provided, which is representative of a vacuum of the tank. The characteristic value is determined as a function of the indicator signal and the predetermined period of time.

A determination of the characteristic value as a function of the predetermined time span has the advantage, for example, that detection of a leak in the tank takes place reliably even if the temperature of the tank or an external influencing factor are inaccurate.

For example, due to the fall in the tank temperature in the given time window, a vacuum would form in a sealed tank. This is verified, for example, in the predetermined period by the indicator signal. However, if the indicator signal does not assume a value characteristic of a vacuum in the tank within the predetermined period of time, it can be assumed that there is a leak in the tank.

In a further advantageous embodiment according to the first aspect, the predetermined time period is between 30 minutes and 90 minutes. In particular, the predetermined period is 60 minutes.

This has the advantage that, in particular, the size and / or the geometry and / or the arrangement of the tank is taken into account, so that a detection of a leak of the tank with high reliability is contributed.

In a further advantageous embodiment according to the first aspect, the predetermined time window is between 5 hours and 10 hours. In particular, the predetermined time window is 7.5 hours.

This has the advantage that, in particular, the size and / or the geometry and / or the arrangement of the tank is taken into account, so that a detection of a leak of the tank with high reliability is contributed. Furthermore, only a limited amount of data is detected by such a length of the predetermined time window, so that due to a resulting low power requirement, a device for performing the method can be produced inexpensively and compactly.

In a further advantageous embodiment according to the first aspect, in each case a predetermined time interval is maintained between the determination of two successive measured values of the at least two measured values. The predetermined time interval is between 30 seconds and 15 minutes. In particular, the predetermined time interval is 10 minutes.

This has the advantage that only a limited number of data is detected, so that due to a resulting low power requirement, an apparatus for performing the method can be implemented inexpensively and compactly. At the same time, however, a sampling rate is small enough to reliably detect a change in the tank temperature.

In a further advantageous embodiment according to the first aspect, the at least two measured values and / or the cumulative rise and / or the fall in the predetermined time window are stored as respective entries in a memory. When the predefined time window is shifted in time with the current time as the start of the predefined time window, at least the entries from the memory whose corresponding time of the determination lies ahead of the current time are deleted from the memory.

This has the advantage that only a limited amount of data must be stored, so that the memory can be produced inexpensively and in a space-saving manner.

According to a second aspect, the invention is characterized by a device for detecting a leak of a tank of a vehicle, which is designed to carry out the method according to the first aspect or an advantageous embodiment of the method.

According to a third aspect, the invention is characterized by a computer program product comprising executable program code, wherein the program code executes the method according to the first aspect or an advantageous embodiment of the method when executed by a data processing device.

In particular, the computer program product comprises a medium which can be read by the data processing device and on which the program code is stored.

Embodiments of the invention are explained below with reference to the schematic drawings. Show it:

1 a system for detecting a leak of a tank of a vehicle,

2 a flowchart of a method for detecting a leak of the tank of the vehicle,

3 a first time course of a tank temperature, and

4 a second time course of the tank temperature.

Elements of the same construction or function are provided across the figures with the same reference numerals.

1 shows a system for detecting a leak of a tank 3 of a vehicle 1 , In the embodiment, the vehicle 1 an internal combustion engine, not shown, which, for example, via leads from the tank 3 is supplied with fuel. Basically, the vehicle 1 not limited to a specific vehicle type. The tank described in the embodiment 3 is a fuel tank. In other embodiments, the tank is 3 any fluid container.

The Tank 3 is sealed such that leakage of a fluid from an interior of the tank 3 , in particular escape of fuel vapor is avoided. To a tightness of the tank 3 check the tank points 3 For example, a so-called natural vacuum leak detection (NVLD) detection. This includes a switch 5 , a temperature sensor 7 and a control unit 9 , In the exemplary embodiment, these are formed in a structural unit which, for example, in addition to a ventilation and / or ventilation of the tank 3 is trained.

The desk 5 is for example designed as a vacuum pressure switch, which assumes a first state in the case of a vacuum in the tank 3 and otherwise assumes a second state. In this context, the term "vacuum" also refers to a condition of the tank 3 used to which only a greatly reduced pressure in the tank 3 relative to an atmospheric pressure prevails. For example, depending on the state, the switch 5 provides an indicator signal I representative of a vacuum in the tank 3 , For example, in the case of a vacuum, the indicator signal I assumes a Boolean value True and otherwise the Boolean value False.

By means of the temperature sensor 7 is a measured value M1, M2 can be determined, which is representative of a tank temperature T of the tank 3 at a current time t of detection.

A temperature change in a closed container basically leads to a pressure change. Depending on a change in the tank temperature T in the tank 3 For example, depending on the indicator signal I, it is possible to determine whether there is a leak in the tank 3 is present, since in a container without leakage from exceeding a limit of the temperature change, the indicator signal I assumes the value, true '.

The control unit 9 is for example signal-wise with the switch 5 and the temperature sensor 7 coupled. Furthermore, the control unit comprises 9 for example, a data and program memory. In this example, the measured value M1, M2 of the temperature sensor 7 stored. Further, in the data and program memory of the control unit 9 For example, steps of a method for detecting a leak of the tank 3 of the vehicle 1 stored as a program, as described below with reference to the flowchart of 2 explained in more detail.

The program is started in a step S0. For example, a start of the program is triggered by an engine of the vehicle 1 is set in an off state. Here, for example, as the reference time for a start of the program, an engine-off time T1 is determined, to which the engine of the vehicle 1 is switched to the off state. In particular, this is a time at which an ignition system of the vehicle 1 is set in an off state, so that it can be assumed that the engine remains at least for a limited period in the off state.

For example, the engine of the vehicle generates 1 in a switched-on state heat, which causes the tank temperature T increases. In addition, the tank temperature T is influenced, for example, by an ambient temperature and / or a solar radiation. From the engine-off point in time T1, it can be assumed that the tank temperature T stagnates, for example, initially and then decreases in the further course. The program is continued in a first step S1.

For example, a predetermined waiting time Tw is maintained between the engine off time T1 and the first step S1, for example, a stagnation phase of the tank temperature T or a temperature rise due to a delay of a temperature line from the engine to the tank 3 to consider.

For example, the temperature sensor 7 and / or the control unit 9 for the predetermined waiting time Tw in a power saving mode. The default waiting time is between 1 minute and 180 minutes. In the embodiment, the predetermined waiting time is 90 minutes.

In the first step S1, a plurality of measured values M1, M2 of the tank temperature T are determined in a predetermined time window Tf. A start T2 of the predetermined time window Tf, for example, initially coincides directly with a sequence of the predetermined waiting time Tw. For example, the measured values M1, M2 are determined at a distance from a predefined time interval T1 to an end time T4 of the predefined time window Tf.

The predetermined time window Tf is for example between 5 hours and 10 hours. In the embodiment, the predetermined time window Tf is 7.5 hours. The predetermined time interval T1 between two successive measured values M1, M2 is, for example, between 30 seconds and 15 minutes. In the embodiment, the predetermined time interval T1 is 10 minutes. In the exemplary embodiment, a maximum of 46 measured values M1, M2 are determined in the predefined time window Tf, which are stored in the data and program memory of the control unit 9 be filed.

Depending on the measured values M1, M2, a cumulative increase D + of the tank temperature T and a drop D- of the tank temperature T are determined. For this purpose, for example, a difference of the measured values M1, M2 is formed.

The cumulative increase D + at a current time t results, for example, from a sum of the differences between successive measured values M1, M2 from the beginning T2 of the predefined time window Tf up to the current time t, which represent a temperature increase, ie the respective difference, for example takes a positive value. Thus, only a temperature rise is determined, regardless of any other course of the tank temperature T within the predetermined time window Tf.

In the case that the cumulative increase D + of the tank temperature T exceeds a predetermined first threshold value Dmax, the predetermined time window Tf is shifted in time and the first step S1 is repeatedly performed.

For example, for this purpose, a first time T + is determined at which the cumulative increase D + exceeds the predetermined first threshold Dmax and the beginning T2 of the predefined time window Tf is shifted in time to the first time T +. The cumulative increase D +, for example, assumes a positive value when the vehicle is exposed to solar radiation, as a result of which the tank temperature T increases. If the predetermined first threshold value Dmax is exceeded, a point in time at which a vacuum is formed can only be predicted with little certainty, so that, in order to increase the reliability of the method, a further drop in temperature is postponed by shifting the predefined time window Tf.

The predetermined first threshold value Dmax is, for example, between 1 ° C and 2 ° C. In the embodiment, the predetermined first threshold Dmax is 1.5 ° C.

The drop D- at the current time t results, for example, as the amount of a difference between one of the measured values M1, M2 at the beginning T2 of the predefined time window Tf and one of the measured values M1, M2 at the current instant t. The waste D- thus represents a temperature difference in the predetermined time window Tf, regardless of the other course of the tank temperature T in the predetermined time window Tf.

In the event that the temperature drop D- at the end time T4 of the predetermined time window Tf is less than the predetermined second threshold Dmin, the beginning T2 of the predetermined time window Tf is shifted in time to the end time T4 and the first step S1 is performed repeatedly. For example, it is ensured that a time of formation of a vacuum with high certainty can be predicted. To increase the reliability of the method, a further temperature drop is thus awaited by shifting the predefined time window Tf.

The predetermined second threshold Dmin is, for example, between 5 ° C and 8 ° C. In the embodiment, the predetermined second threshold Dmin is 6 ° C.

In the event that the drop D- of the tank temperature T exceeds a predetermined second threshold value Dmin, the program is continued in a second step S2.

In the second step S2, a time span start T3 is determined at which the drop D- of the tank temperature T exceeds the predetermined second threshold value Dmin. At the beginning of the period T3, the tank temperature T has dropped such that with the formation of a vacuum in the tank 3 is to be expected.

In the event that within a predetermined period of time Tc from the time span beginning T3 of the switch 5 assumes the first state, the tank indicates 3 no leak on. A characteristic S, which is representative of the leak of the tank 3 In this case, for example, the Boolean value "False" is assigned and the program is terminated. Remains the switch 5 however, for a total duration of the predetermined period of time Tc unchanged in the second state, there is a leak of the tank 3 in front. The characteristic value S is then assigned, for example, the Boolean value, true 'and the program is terminated.

The predetermined period of time Tc is for example between 30 minutes and 90 minutes. In the embodiment, the predetermined time Tc is 60 minutes.

In the event that, within the predetermined time period Tc, a rise in temperature causes the accumulated increase D + to exceed the predetermined first threshold value Dmax, the corresponding first instant T + is determined. In this case, the beginning T2 of the predetermined time window Tf is shifted in time to the first time T +, and the first step S1 is repeatedly performed.

Alternatively and / or additionally, in the event that the drop D falls below the predetermined second threshold value Dmin within the predetermined time period Tc, a corresponding second time T- is determined. In this case, the beginning T2 of the predetermined time window Tf is shifted in time to the second time T- and the first step S1 is repeatedly performed.

When shifting the beginning T2 of the predetermined time window Tf, for example, the measured values M1, M2 from the data and program memory of the control unit 9 deleted, the corresponding current time t of the determination is temporally before the beginning of T2. Advantageously, such a data and program memory of the control unit 9 with extremely low storage capacity.

In the event that no characteristic value S has been determined even after several times of shifting the predetermined time window Tf, for example after the expiration of 24 hours since the engine-off time T1, the program is ended.

3 and 4 each show a time course of an exemplary tank temperature T over a period of 24 hours. At the engine off time T1, it is observed that the tank temperature T continues to increase. Therefore, first the waiting time Tw is waited for, in which the control unit, for example, enters a power-saving mode.

After expiration of the waiting time Tw, the tank temperature T continues to rise, the predetermined first threshold Dmax is exceeded at the first time T +. The beginning T2 of the predetermined time window Tf is therefore shifted in time until the tank temperature T drops.

Within the predetermined time window Tf, the tank temperature T finally drops so long that the predetermined second threshold value Dmin is exceeded. Corresponding thereto, the time span beginning T3 is determined, at which the predetermined time period Tc begins. Since the tank temperature T does not increase within the predetermined time period Tc, ie in particular neither the drop D- falls below the second threshold value Dmin, nor does the cumulative increase D + exceed the first threshold value Dmax, the state of the switch is 5 in the predetermined period Tc representative of a leak in the tank 3 of the vehicle 1 , In case of the switch 5 does not assume a state representative of a vacuum in the tank within the predetermined period of time 3 , despite the required temperature change could not form a vacuum and the tank 3 has a leak. The program will then be terminated.

For the sake of clarity, the end time T4 of the predefined time window Tf is plotted in each case for the further course of the tank temperature T after the predetermined time period Tc. At this time, if the drop D- of the tank temperature T is less than the predetermined second threshold Dmin, the beginning T2 of the predetermined time window Tf is shifted to the end time T4 of the previous predetermined time window Tf.

In 3 Furthermore, the second time T- is shown at which the drop D- of the tank temperature T falls below the predetermined second threshold value Dmin. Also in this case, the predetermined time window Tf is shifted.

LIST OF REFERENCE NUMBERS

1

vehicle

3

tank

5

switch

7

temperature sensor

9

control unit

S0 ... S2

program steps

T1

Engine shut-off time

T2

beginning

T3

Periods beginning

T4

end time

tf

Time window

tc

Period of time

tw

waiting period

Ti

time interval

T +

first time

T-

second time

T

tank temperature

M1, M2

readings

D +

cumulative increase

D-

waste

Dmax

first threshold

Dmin

second threshold

I

indicator signal

S

characteristic value

Claims (11)

Method for detecting a leak in a tank ( 3 ) of a vehicle ( 1 ), in which - in a first step (S1) between a start (T2) and an end time (T4) of a predetermined time window (Tf) at least two measured values (M1, M2) of a tank temperature (T) are determined, depending on which a cumulative Rise (D +) of the tank temperature (T) and a drop (D) of the tank temperature (T) in the predetermined time window (Tf) are determined, wherein - in the case that a predetermined first threshold (Dmax) by the cumulative increase (D + ) is exceeded, a corresponding first time (T +) is determined, to which the beginning (T2) of the predetermined time window (Tf) is shifted in time and the first step (S1) is repeatedly performed, and / or - in the case that Drop (D-) at the end time (T4) is less than a predetermined second threshold (Dmin), the beginning (T2) of the predetermined time window (Tf) is shifted in time to the end time (T4) and the first step (S1) is repeated carried out and in the case where the drop (D-) exceeds the predetermined second threshold value (Dmin), in a second step (S2), starting from a time span (T3) at which the drop (D-) reaches the predetermined second threshold value (T) ( Dmin), a state of a characteristic value (S), which is representative of the leak of the tank, is determined within a predetermined period of time (Tc) ( 3 ), wherein - in the event that the predetermined first threshold value (Dmax) is exceeded by the accumulated increase (D +) after the start of the period (T3), the corresponding first time (T +) is determined, to which the beginning (T2) of the predetermined Time window (Tf) is shifted in time and the first step (S1) is repeatedly performed, and / or - in the case that the drop (D-) after the time span start (T3) below the predetermined second threshold (Dmin), a corresponding second Time (T) is determined, to which the beginning (T2) of the predetermined time window (Tf) is shifted in time and the first step (S1) is performed repeatedly. Method according to Claim 1, in which - an engine-off point in time (T1) is determined, to which an engine of the vehicle ( 1 ), and the first step (S1) is executed after a predetermined waiting time (Tw) after the motor-off time (T1), wherein the predetermined waiting time (Tw) is between 1 minute and 180 minutes , Method according to one of the preceding claims 1 to 2, wherein the predetermined first threshold value (Dmax) is between 1 ° C and 2 ° C. Method according to one of the preceding claims 1 to 3, wherein the predetermined second threshold value (Dmin) is between 5 ° C and 8 ° C. Method according to one of the preceding claims 1 to 4, in which an indicator signal (I) is provided, which is representative of a vacuum of the tank ( 3 ), wherein the characteristic value (S) is determined depending on the indicator signal (I) and the predetermined period of time (Tc). Method according to one of the preceding claims 1 to 5, wherein the predetermined period of time (Tc) is between 30 minutes and 90 minutes. Method according to one of the preceding claims 1 to 6, wherein the predetermined time window (Tf) is between 5 hours and 10 hours. Method according to one of the preceding claims 1 to 7, in which a predetermined time interval (T1) is maintained between the determination of two successive measured values of the at least two measured values (M1, M2) which is between 30 seconds and 15 minutes. Method according to one of the preceding Claims 1 to 8, in which the at least two measured values (M1, M2) and / or the cumulative increase (D +) and / or the fall (D) in the predetermined time window (Tf) are recorded as respective entries in a memory are stored, wherein at a time shift of the predetermined time window (Tf) at least the entries are deleted from the memory whose corresponding time of the determination is temporally before the beginning (T2). Device for detecting a leak in a tank ( 3 ) of a vehicle ( 1 ) which is adapted to carry out the method according to one of claims 1 to 9. A computer program product comprising a readable by a data processing device medium, is stored on the executable program code, the program code when executed by the data processing device carries out the method according to one of claims 1 to 9.

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