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Title:
METHOD AND SYSTEM FOR DETECTING WAXING OF DIESEL FUEL IN A FUEL TANK IN A MOTOR VEHICLE
Document Type and Number:
WIPO Patent Application WO/2012/169957
Kind Code:
A1
Abstract:
Method and system for detecting waxing of diesel fuel in a fuel tank (4) in a motor vehicle (2). Measured values from temperature sensors (8a, 8b) are used to generate a first temperature value which represents the temperature of the fuel in a first region (4a) of the tank,and a second temperature value which represents the temperature of the fuel in a second region (4b) of the tank. A differential value which represents the prevailing difference between the first temperature value and the second temperature value is determined and is compared with a limit value for detection of waxing of the fuel in the tank.

Inventors:
ERIKSSON, Henrik (Laggkärlsvägen 11, Huddinge, S-149 59, SE)
ROOS, Stefan (Edåsdalen 720, Undersåker, S-830 10, SE)
Application Number:
SE2012/050600
Publication Date:
December 13, 2012
Filing Date:
June 05, 2012
Export Citation:
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Assignee:
SCANIA CV AB (S- Södertälje, 151 87, SE)
ERIKSSON, Henrik (Laggkärlsvägen 11, Huddinge, S-149 59, SE)
ROOS, Stefan (Edåsdalen 720, Undersåker, S-830 10, SE)
International Classes:
G01N25/04; B60K15/03; F02M37/22; G01N33/28
Domestic Patent References:
2009-01-15
Foreign References:
US20050053116A12005-03-10
GB1029165A1966-05-11
US20100012410A12010-01-21
US4770540A1988-09-13
EP1900915A12008-03-19
Other References:
See also references of EP 2718702A4
Attorney, Agent or Firm:
WESTMAN, Mimmi (Scania CV AB, Södertälje, S-151 87, SE)
Download PDF:
Claims:
A method for detecting waxing of diesel fuel in a fuel tank (4) in a motor vehicle (2) , characterised in that the method comprises the following steps:

- using measured values from temperature sensors (8a, 8b) to generate a first temperature value (VTi) which represents the temperature of the fuel in a first region (4a) of the fuel tank, and a second temperature value (VT2) which represents the temperature of the fuel in a second region (4b) of the tank,

- determining a differential value (Vdiff) which represents the prevailing difference between the first temperature value (VTi) and the second temperature value (VT2) , and

- comparing the differential value (Vd iff) with a limit value (VG) for detection of waxing of the fuel in the tan k (4).

A method according to claim 1 , characterised in that waxing of the fuel in the tank (4) is detected when it is found that the differential value (Vdiff) has an absolute value greater than or equal to the limit value (VG).

A method according to claim 1 or 2 , characterised in that a warning signal or a message which indicates waxing of the diesel fuel is generated when such waxing is detected .

A method according to any one of claims 1 -3, characterised in that one or more fuel heaters (9) are activated to warm the fuel when waxing of the fuel is detected .

A system for detecting waxing of diesel fuel in a fuel tank in a motor vehicle, characterised

- in that the system (10) comprises an electron ic data processing device (1 1 ) adapted to using measured values from temperature sensors to generate a first temperature value (VJI) which represents the temperature of the fuel in a first region of the tank, and a second temperature value (VT2) which represents the temperature of the fuel in a second region of the tank,

- that the data processing device (11) is adapted to determining a differential value (Vdiff) which represents the prevailing difference between the first temperature value (VTi) and the second temperature value (VT2), and to comparing this differential value (Vdiff) with a limit value (VG) for detection of waxing of the fuel in the tank. 6. A system according to claim 5, characterised in that the data processing device (11) is adapted to detecting waxing of the fuel in the tank when it finds that the differential value (Vdiff) has an absolute value greater than or equal to the limit value

(VG).

7. A system according to claim 5 or 6, characterised in that the data processing device (11) is adapted to generating a warning signal or a message which indicates waxing of the fuel when it detects such waxing.

8. A system according to any one of claims 5-7, characterised in that the data processing device (11) is adapted to activating one or more fuel heaters to warm the fuel when it detects waxing of the fuel.

9. A computer programme comprising computer programme code for causing a computer to implement a method according to any one of claims 1-4 when the computer programme is executed on the computer.

10. A computer programme product comprising a data storage medium which can be read by a computer and on which the programme code of a computer programme according to claim 9 is stored.

11. An electronic control unit of a motor vehicle comprising an execution means (21), a memory (22) connected to the execution means and a data storage medium (24) which is connected to the execution means and on which the computer programme code of a computer programme according to claim 9 is stored .

Description:
Method and system for detecting waxing of diesel fuel in a fuel tank in a motor vehicle

FI ELD OF TH E I NVENTI ON AND PRIOR ART

The present invention relates to a method and a system for detecting waxing of diesel fuel in a fuel tank in a motor vehicle. The invention relates also to a computer programme and a computer programme product comprising computer programme code for implementing a method accord ing to the invention, and to an electronic control unit. When its temperature drops to a certain level , diesel fuel becomes su bject to waxing , which means that wax crystals form in it. The temperature at which this waxing commences is referred to as the fuel's waxing point. In a diesel-powered vehicle the wax crystals which form in its fuel may be trapped in the fuel filter situated between the fuel tank and the eng ine. This leads to the filter being obstructed by the wax crystals and no longer being able to allow necessary amounts of fuel to reach the eng ine, making it difficult or completely impossible for the engine to run. A known way of preventing such obstruction of the fuel filter in a motor vehicle is to activate various kinds of electrically powered fuel heaters when the temperature of the fuel drops to a certain predetermined level, e.g . as described in US 2003/01 16490 A1 and EP 0 412 210 A1 . This warming of the fuel counteracts its waxing . As fuel heaters consume energy when switched on, and thereby cause increased fuel consumption of the vehicle, it is desirable not to have them switched on unnecessarily but only when there is real need .

The waxing point of diesel fuel depends inter alia on various kinds of add itives added to the fuel to g ive it a suitable waxing point. A problem with the abovementioned solution with fuel heaters activated when the fuel is at a certain temperature level is that not only is the waxing point not declared by fuel suppliers but it may also vary from one refuelling to another. The vehicle's driver therefore usually has no accurate knowledge of the prevailing waxing point of the fuel contained in its fuel tan k at the time. This means that the temperature level for activation of fuel heaters has to be chosen with a relatively large safety margin which may lead to their being activated more often than is really necessary. There is of course also a risk of the prevailing waxing point of the fuel in the tank being significantly h igher than expected , potentially leading to heaters not being activated in time to prevent waxing of the fuel and obstruction of the vehicle's fuel filter.

An alternative solution which makes it possible to prevent these latter problems is based on waxing of the diesel fuel being detected on board the vehicle by an optical method , e.g . as described in US 2005/00531 16 A1 . That solution does however involve relatively complex and expensive equ ipment. OBJECT OF TH E I NVENTI ON

The object of the present invention is to propose a novel and advantageous way of detecting waxing of diesel fuel in a fuel tank in a motor vehicle.

SUMMARY OF THE I NVENTION

According to the present invention, said object is achieved by a method with the features defined in claim 1 and a system with the features defined in claim 5.

According to the invention ,

- measured values from temperature sensors are used to generate a first temperature value wh ich represents the temperature of the diesel fuel in a first region of the fuel tank, and a second temperature value wh ich represents the temperature of the diesel fuel in a second region of the tan k, - a differential value representing the prevailing difference between the first temperature value and the second temperature value is determined , and

- the d ifferential value is compared with a limit value for detection of waxing of the diesel fuel in the tan k.

When the temperature of the diesel fuel in the fuel tank drops, heat will be released from the fuel via the sidewalls and bottom of the tank and via the fuel surface. The gradual temperature decrease at the edges of the fuel volume in the fuel tank leads to density differences in the fuel , resulting in circu lation of the fuel in the tank and heat transfer by natural convection . So long as the temperature of the fuel in the tank is above its waxing point, the natural convection will lead to equalisation of its temperature in the tank. The natural convection thus counteracts temperature stratification of the fuel in the tank, which means that there will be no obvious fuel temperature differences in different parts of the tank. When the fuel in the tank reaches a low enough temperature to become subject to waxing , the fuel circulation in the tank and the effectiveness of the natural convection are hindered , so the temperature equalisation will decrease, leading to more obvious fuel temperature differences in d ifferent parts of the tank. By reg istering such temperature differences it therefore becomes possible to detect waxing of the fuel in the tank. The solution according to the invention provides a simple way of detecting waxing of diesel fuel in a fuel tank without having to use other than relatively simple and inexpensive temperature sensors. When waxing of the fuel is detected , a warning signal or a message which indicates the waxing may for example be generated . It is also possible to have one or more fuel heaters activated to warm the fuel when its waxing is detected .

Other advantageous features of the method and system according to the invention are indicated by the independent claims and the description set out below. The invention relates also to a computer programme with the features defined in claim 9, a computer programme product with the features defined in claim 10 and an electronic control unit with the features defined in claim 1 1 .

BRI EF DESCRI PTION OF THE DRAWI NGS

The invention is described below in more detail on the basis of embod iment examples with reference to the attached drawings, in which

Fig . 1 is a schematic diagram of a motor vehicle with a combustion engine and a system according to the present invention for detecting waxing of diesel fuel in the vehicle's fuel tank, is a schematic d iagram of an electronic control unit for implementing a method accord ing to the invention, and Fig . 3 is a flowchart illustrating a method according to an embod iment of the invention.

DETAI LED DESCRI PTION OF EMBOD I MENTS OF THE I NVENTION

Fig . 1 depicts schematically a combustion engine 1 of a motor veh icle 2. A pump 3 is provided to feed diesel fuel to the engine 1 from a fuel tank 4 via a fuel line 5. A fuel filter 6 is provided in the fuel line 5 to filter the d iesel fuel . It is also possible to use two or more fuel filters to filter the diesel fuel , e.g . a first fuel filter situated in the fuel line 5 between the fuel tank 4 and the pump 3 and a second fuel filter situated in the fuel line between the pump 3 and the engine 1 . Fig . 1 depicts schematically a system 10 according to the present invention for detecting waxing of the diesel fuel 7 contained in the vehicle's fuel tan k 4. One or more first temperature sensors 8a are provided to measure the temperature of the diesel fuel in a first region 4a of the fuel tank 4, and one or more second temperature sensors 8b to measure the temperature of the d iesel fuel in a second reg ion 4b of the tank. I n the embodiment depicted in Fig . 1 , said first and second regions 4a, 4b of the tan k are situated at a d istance from one another in a horizontal direction but might alternatively be at a distance from one another in a vertical d irection or in both horizontal and vertical directions.

The system 10 according to the invention comprises an electron ic data processing device 1 1 connected to said temperature sensors 8a, 8b in order to receive from them measured values for the temperature of the diesel fuel 7 in said first and second reg ions 4a, 4b of the fuel tank.

The electron ic data processing device 1 1 is adapted to using measured values from said temperature sensors 8a, 8b to generate a first temperature value V T i which represents the temperature of the fuel in said first region 4a of the fuel tank, and a second temperature value V T 2 which represents the temperature of the fuel in said second region 4b of the tank. The data processing device 1 1 is further adapted to determin ing a differential value V d if f which represents the prevailing difference between the first temperature value V T i and the second temperature value V T 2 , and to comparing this differential value V d i ff with a limit value V G for detection of waxing of the fuel. The differential value V d if f is with advantage calculated as the difference V d if f= V T i-V T 2 or the difference V d if f= V T 2-V T i , and waxing of the fuel is detected when it is found that the d ifferential value V d iff has an absolute value greater than or equal to the limit value V G . The limit value V G is chosen such as to be somewhat greater than the small fuel temperature differences wh ich may normally occur between the two regions 4a, 4b of the tank 4 before the temperature of the fuel drops low enough for waxing to occur.

When the data processing device 1 1 detects waxing , i .e. when the aforesaid comparison between the differential value V diff and the limit value V G shows that the diesel fuel 7 in the tank 4 has undergone waxing , the data processing device 1 1 is adapted to activating one or more fuel heaters 9 to warm the fuel . Warming the fuel by means of said fuel heaters counteracts continued waxing of the fuel and dissolves the wax crystals already formed . In the example depicted , the heater 9 is situated within the tank 4. As an alternative or in add ition to the heater 9 situated in the tank, fuel heaters might be provided on the outside of the tan k, to warm from outside the fuel 7 contained in the tank, and/or be provided in the fuel filter 6 and/or in the fuel line 5 between the tan k and the filter. Each fuel filter wou ld with advantage be powered electrically and might for example comprise one or more electrical heating elements. When waxing is detected , the data processing device 1 1 may also be adapted to generating a warning signal, e.g . in the form of a visual or acoustic signal, or a message wh ich ind icates waxing of the fuel. A driver in the vehicle 2 may thus for example be made aware that the fuel has undergone waxing .

The aforesaid data processing device 1 1 may be implemented by means of a single electronic control unit of the vehicle 2, as depicted in Fig . 1 , but might alternatively be implemented by means of two or more mutually cooperating electronic control units of the veh icle.

Fig . 3 is a flowchart illustrating an embod iment of a method according to the present invention for detecting waxing of d iesel fuel 7 in a fuel tank 4 in a motor veh icle 2.

As a first step S 1 , measured values from temperature sensors 8a, 8b are used to generate a first temperature value V T i which represents the temperature of the fuel 7 in a first region 4a of the fuel tank, and a second temperature value V T 2 which represents the temperature of the fuel in a second region 4b of the tank.

As a second step S2 , a differential value V d if f representing the prevailing difference between the first temperature value V T i and the second temperature value V T 2 is determined .

As a third step S3, the differential value V d if f is compared with a limit value V G for detection of waxing of the fuel in the fuel tank. If the comparison at step S3 shows that the fuel has not undergone waxing , steps S 1 -S3 are repeated after a certain period of time.

If the comparison at step S3 shows that the fuel has undergone waxing , one or more fuel heaters for warming the fuel are activated as a fourth step S4. Computer programme code for implementing a method according to the invention is with advantage included in a computer programme which can be read into the internal memory of a computer, e.g . the internal memory of an electronic control unit of a motor vehicle. Such a computer programme is with advantage provided via a computer programme product comprising a data storage medium which can be read by a computer and which has the computer programme stored on it. Said data storage med ium is for example an optical data storage med ium in the form of a CD ROM d isc, a DVD disc etc. , a magnetic data storage medium in the form of a hard d isc, a diskette, a cassette tape etc. , or a flash memory or a memory of the ROM , PROM , EPROM or EEPROM type.

Fig . 2 illustrates very schematically an electron ic control unit 20 comprising an execution means 21 , e.g . a central processor un it (CPU), for execution of computer software. The execution means 21 communicates with a memory 22, e.g . of the RAM type, via a data bus 23. The control unit 20 comprises also a data storage medium 24, e.g . in the form of a flash memory or a memory of the ROM , PROM , EPROM or EEPROM type. The execution means 21 commun icates with the data storage med ium 24 via the data bus 23. A computer programme comprising computer programme code for implementing a method accord ing to the invention , e.g . in accordance with any of the embodiments illustrated in Figs. 3 and 4, is stored on the data storage medium 24.

The invention is of course in no way restricted to the embodiments described above, since many possibilities for modifications thereof are likely to be obvious to one skilled in the art without therein having to deviate from the invention's basic concept such as defined in the attached claims.