DE102006004296A1 - Detecting faults in vehicle fuel pump with filter, compares electrical power input with hydraulic pumping performance and identifies departures outside given thresholds - Google Patents

Abstract

Hydraulic performance (Phyd) in the fuel system and electric power (Pel) consumed by the electric fuel pump (34) are compared with each other. On departure from given values and/or on exceeding or falling below given threshold values, an error state is deduced. Unacceptable operation of the filter (32) and/or pump is identified, should the efficiency eta derived from the values (Phyd, Pel) fall below a given threshold.

Description

The The invention relates to a method for determining an error condition a fuel delivery system with a fuel filter according to the preamble of claim 1.

By the introduction Regulated electric fuel pumps (EKP) for motor vehicles becomes a controller needed for speed control of the electric fuel pump. at Regulated systems is a pressure sensor for actual pressure detection necessary. Furthermore, information is provided by the engine control unit, that improve the regulation.

The associated Fuel filters are often used today for space reasons the tank is integrated so that the filter replacement in case of contamination getting more expensive. There are already tank variants available in which the fuel filter can only be exchanged a few more times can and after several exchange intervals a complete tank exchange necessary becomes. These tank variants are already using so-called "livetime" fuel filters equipped, in which usually no filter replacement provided is. However, it has been shown that these fuel filters in countries with poor fuel quality not this necessary long Lifetime fulfill and by pollution damage can cause on the internal combustion engine.

From the publication DE 198 28 933 A1 a filter charge detection in a fuel system by evaluating the pressure drop at the fuel filter is known in which the fuel delivery pump is included in the diagnostic device. It is a system with a mechanical pressure regulator and constant system pressure. For diagnosis, the supply current is measured via the voltage drop across the electrical supply line to the fuel delivery pump. As the system pressure changes, the voltage drop increases. The method can not be used with volume- or pressure-controlled systems.

From the publication DE 199 35 237 A1 is a load detection by determining the pressure difference before and after the fuel filter known. An engine control unit calculates a set pressure from characteristic curves and maps. After the fuel filter actual pressure is measured. If this deviates from a desired pressure, a correction of control variables of the engine to filter loading is concluded. The engine control unit is connected to only one setting unit for the electric fuel pump.

The publication DE 38 39 960 A1 discloses a filter charge detection by evaluating the output of a voltage applied to the residue sensor. The sensor is integrated in the fuel filter and has a variable resistance depending on the pollution.

task The invention is a method for determining an operating condition a fuel delivery system with a fuel filter and a fuel pump to provide which can be used flexibly and allows a diagnosis of various fault conditions.

The The object is achieved by the Characteristics of claim 1 solved.

The inventive method for detecting a fault condition of a fuel delivery system for supplying an internal combustion engine provides that a hydraulic Power in the fuel system and electrical power of the electric fuel pump compared with each other and deviating from predetermined Values and / or exceeding or falling below predetermined thresholds an error condition is derived.

Around to diagnose the electric fuel pump for failure e.g. electrical voltages, electrical currents and also the pulse width modulated Signal (PWM) to control the electric fuel pump measured.

• – Es kann ein erhöhter Widerstand in Förderleitung nach der elektrischen Kraftstoffpumpe bestimmt werden. Der erhöhte Widerstand kann durch Leitungsreduktion (Knick, Quetschung), beladener Kraftstofffilter (vor oder nach der elektrischen Kraftstoffpumpe), Verschleiß an der elektrischen Kraftstoffpumpe, nicht funktionsfähige Rückschlagventile, beschädigte Quick-Konnektoren (Leitungsverbindern) usw. entstehen. Es kann ein reduzierter Widerstand in der Förderleitung nach der elektrischen Kraftstoffpumpe detektiert werden. Dadurch kann ein Leitungsbruch oder eine Leckage erkannt werden. Es kann ein erhöhter Widerstand vor der elektrischen Kraftstoffpumpe detektiert werden. Dadurch ist es möglich zu erkennen, ob der Vorfilter zugesetzt ist. Es kann eine Fehlfunktion an Saugstrahlpumpen, welche Kraftstoff im Tank fördern, detektiert werden. Dadurch können Saugstrahlpumpen auf Verstopfung und undefinierte Öffnungen diagnostiziert werden. Hierzu kann sowohl die Saugstrahlpumpe im Sammeltopf als auch eine bei Satteltanks gegenüberliegende Saugstrahlpumpen diagnostiziert werden.

Advantageously, the existing components and the existing communication to the control unit of the internal combustion engine can be used to detect an incorrect hydraulic resistance. Various error conditions can be detected, whereby different suitable countermeasures are triggered.

• - It can be an increased resistance in the delivery line after the electric fuel pump can be determined. The increased resistance may be due to conduction reduction (kink, crush), loaded fuel filter (before or after the electric fuel pump), wear on the electric fuel pump, non-functioning check valves, damaged quick connectors (line connectors), etc. A reduced resistance in the delivery line after the electric fuel pump can be detected. As a result, a line break or leakage can be detected. An increased resistance in front of the electric fuel pump can be detected. This makes it possible to detect whether the pre-filter is added. It may be a malfunction of suction jet pumps, which promote fuel in the tank, are detected. As a result, suction jet pumps can be diagnosed for constipation and undefined openings. For this purpose, both the suction jet pump in the collecting pot as well as a suction jet pumps opposite the saddle tanks can be diagnosed.

By the detection of an increased Hydraulic resistance at the fuel filter can be avoided in which situations through under-funding Engine damage, So-called couch bumpers (unable to drive breakdown vehicles) and / or Escape of fuel economic or personal damage arises. By elevated Resistance becomes more unnecessary Wear on caused the electric fuel pump, although the user not noticed. At elevated Wear the electric fuel pump e.g. for critical fuels (coking the collector) can be a total failure of the electric fuel pump be clearly prediagnosed with the result of the reduction of Lying and customer complaints. Also can by a Filter loading detection a filter replacement timely displayed or unnecessary Exchange actions are prevented. Here is the function (filter loading) be extended with a mileage function (range).

By the detection of a reduced hydraulic resistance can at Line break (shutdown, assembly error, etc.) the fuel pump immediately be switched off. For small leaks e.g. in the tank and difficult to notice, an information or error entry respectively. When operating the electric fuel pump without fuel and lack of pressure build-up, the electric fuel pump can be switched off to ensure, for example, dry run protection. This causes damage to fires avoided the electric fuel pump.

By the function of increased Resistance before the electric fuel pump can be a loaded and / or clogged pre-filter can be detected, which is not comparable to laden front fuel filter. Prefilter are in the Usually not for the exchange in the service area provided and cause at high Loading fuel pump damage, engine damage or lying down.

By The supervision the one or two Saugstrahlpumpen in a saddle tank can at Clogged suction jet pump, a decrease in the level in the collection pot and / or a lack of pumping the two saddle tanks are detected. By Pressure increase can be a flushing or again a safe Set function. Furthermore, it can also be detected by a leaking suction jet pump become.

Favorable price and further developments of the invention are the further claims remove

Further Advantages and details of the invention are described below a preferred embodiment described in the drawing explained in more detail, without to this embodiment limited to be.

there demonstrate:

1a , b; two alternative embodiments of a preferred saddle tank in which a suction jet pump is mounted in front of a fuel filter (a) and in which a suction jet pump is arranged behind a fuel filter (b),

2 a pressure loss via a fuel filter as a function of a running distance,

3 a flow characteristic through a fuel filter with a differential pressure curve over a flow, and

4 Voltage-dependent current and volumetric flow characteristics of an electric fuel pump.

at all of the detected error conditions described below Fuel filter or conveyor system can the driver for example, information or warning Combi instrument be given, and / or an error entry in a control unit respectively.

It is a method according to the invention for Detection of an altered hydraulic resistance by power measurement of electrical and hydraulic power of an electric fuel pump described.

The 1a and 1b show alternative embodiments of a trained as a saddle tank fuel tank 10 with a first tank section 12 and a second tank section 14 , In the first tank section 12 is a first suction jet pump 16 , in the second tank section 14 a second suction jet pump 18 arranged. An electric fuel pump 34 is in the first tank section 12 arranged. Before the first suction jet pump 16 is a pre-filter 20 arranged. prefilter 20 , Suction jet pump 16 and fuel pump sit in a separate collection pot 48 , The first suction jet pump 16 sits directly on the electric fuel pump 34 arranged.

In the second tank section 14 is a fuel filter 32 arranged as well as a second suction jet pump 18 , The fuel filter 32 has a pressure relief valve 38 with a drain on. A pressure sensor 44 is on the fuel filter 32 arranged.

A return line 22 leads from the second suction jet pump 18 to the collection pot 48 and a supply line 24 from the electric fuel pump 34 to the fuel filter 32 from which a supply line 36 to an internal combustion engine 30 leads, which is to be supplied with fuel. A suction jet supply line 46 between fuel filter 32 and second suction jet pump 18 leads the suction jet pump 18 Fuel to perform their pumping function too.

A tank controller 28 is with an electrical line 40 with the electric fuel pump 34 and with an electrical line 42 with the pressure sensor 44 connected, and with an unspecified line to the internal combustion engine 30 ,

In the embodiment according to 1a goes the pump jet line 46 the second suction jet pump 18 directly from the in an entrance opening 26 of the fuel filter 32 opening feed line 24 from.

In the embodiment according to 1b branches the suction jet supply line 46 the second suction jet pump 18 from the fuel filter 32 off, and the second suction jet pump 18 is downstream to the fuel filter 32 arranged.

In alternative, not graphically executed arrangements, the first suction jet pump 16 from the supply line 24 operated, or for example the output of the pressure relief valve 38 in the return line 22 lead. Likewise, a cubically formed fuel tank 10 be used with only one suction jet pump whose Verschaltungsmöglichkeiten are diverse. There may also be two electric fuel pumps 34 be connected in parallel or in series to meet higher requirements. It is also conceivable, because pressure sensor in the flow line 36 to the internal combustion engine 30 to arrange.

_According to the invention, a hydraulic power P _{hyd is} determined by the measured pressure at the pressure sensor 44 , after the fuel filter 32 is involved, and the Verbraussignal the internal combustion engine 30 calculated via CAN. The calculated value of hydraulic power P _hyd is compared with the calculated value of electric power P _el .

The electric power P _el can be measured by measuring the electric voltage and the electric current of the electric fuel pump 34 be calculated. It is also possible, by the PWM ratio (pulse width modulation), the supply voltage and the voltage set therefrom to the electric fuel pump 34 to give a statement about the electric power P _el .

Both powers P _hyd and P _el are compared with each other. In the event of a deviation from specified values, for example from individual interpolation points or from a characteristic over the entire range of both pressure and volume, an increased or reduced hydraulic resistance can be detected.

It is unimportant whether the supplied internal combustion engine 30 another high-pressure pump or is supplied directly via the so-called "fuel rail." It does not matter whether the fuel is a diesel or petrol or an alternative fuel.

In pre-run systems, the proportionality between electrical and hydraulic power P _el and P _hyd can be applied as described 1: 1. In return systems, where there is typically a high filter flow rate, a constant for the return flow rate must be introduced. But because of the high throughput, the pressure drop is significantly greater, an equally good resolution is possible.

The effect is explained by an example calculation: Power electric P el = U · I [W] Power hydraulic P hyd = Q · p / 36 (The factor 36 is a conversion factor of the units)

P

= Leistung [W]

U

= Spannung [V]

I

= Strom [A]

Q

= Kraftstoffvolumendurchsatz [l/h]

p

= Druck in [bar] (relativ zur Umgebung)

The efficiency of the system is η = P _hyd / P _el

P

= Power [W]

U

= Voltage [V]

I

= Current [A]

Q

= Fuel volume flow rate [l / h]

p

= Pressure in [bar] (relative to the environment)

The hydraulic power P _hyd is always constant at a constant pressure at a given volume, eg at 40 liters total power (eg 21 liters suction jet pump and 19 liters consumption of the vehicle), such as 2 shows, results in a hydraulic power P _hyd of P hyd = 40 x 3.8 / 36 = 4.22 watts hyd

For this purpose, then an electric power P _el of P el = 6.0 V · 9.4 A = 56.4 watts el to adjust.

This results in an efficiency η of η = P hyd / P el = 4.22 / 56.4 = 7.48%

Is now a filter loading of the fuel filters 34 of 300-400 mbar, which corresponds to a typical value after a mileage about 100 000 km, as in 2 shown, can be used to convert the data of the curves in 4 be used. The data can be obtained, for example, by test measurements on different filter types and in the tank control unit 28 be stored.

2 shows the pressure loss DV over the fuel filter 34 as a function of the running distance s with a dirt capacity of 7.7 grams (SK7.7) or 2.5 grams (SK2.5) of the fuel filter 32 , 4 shows the current flow and the corresponding fuel volume flow rate over the voltage.

The hydraulic power P _hyd does not change since 40 liters are still delivered at 3.8 bar. It only results in a different electrical power P _el of P el = 6.5V · 10.4A = 67.6W el

This results in an efficiency of η = P hyd / P el = 4.22 / 67.6 = 6.2%.

The Deterioration of approx. 1.3% corresponds to a relative deterioration from 21% (1.3% to 6.2%).

These Deviations can through downstream functions to those described below Diagnoses are used.

A loading condition of the fuel filter 32 and a slow closure of the leading fuel lines 24 . 26 can be recognized. For this purpose, preferably permanently, the hydraulic power P _{hyd is compared} with the electrical power P _el . This can be done in selected bases or over the entire area (pressure and volume).

In 3 It can be seen that the difference is clearly better at high volume flows (curve A) than at low flow rates (curve B). Thus, a clocked measurement at high volume flows (acceleration) is advantageous. By default or by Fuzzi logic, a start value (efficiency of the new system) is deposited.

In 2 the increase of the pressure difference DV over the running distance s can be recognized. By several measurements, a slow drop in the efficiency η can be detected. Individual outliers are prevented by eg averaging over a running distance s or the time. If the efficiency η falls below a predetermined threshold, an increased hydraulic resistance is detected.

Optionally, the PWM ratio can also be included. If a PWM ratio of 100% is required for a hydraulic power P _hyd to be achieved, the _status can also be recognized. In this case, however, the on-board voltage must be taken into account, since this function can trigger incorrect reductions in the case of low voltage.

Furthermore, leaks or line break can be detected. When the electric fuel pump 34 an electric power P _{el is} supplied and the hydraulic power P _{hyd collapses suddenly} by a pressure reduction, a line _break can be detected, and the electric fuel pump 34 can be deactivated.

Controls the electric fuel pump 34 for a period of time x, and no pressure builds up, leakage may also be inferred. With this function, the dry run is also covered, so that a burn through of the electric fuel pump 34 or unnecessary wear is avoided.

In overrun phases, the internal combustion engine requires 30 usually no flow volume in the flow line 36 so that's from the electric fuel pump 34 delivered volumes only for the drive volume of the suction jet pumps 16 . 18 is needed. Here, the arrangement of the second suction jet pump plays 18 as in the 1a and 1b shown, no matter.

At hydraulic powers P _hyd of 0 (due to volume flow 0), the electric power P _{el is} compared with two threshold values. If the power P _el below the threshold, one can of a closure of the suction jet pump 16 and or 18 output and eliminate it by an increase in pressure if necessary. The function must be deactivated when the voltage is above a further threshold, as this function also works in the event of fuel shortage. If the threshold is above the upper threshold, one can assume a leakage in the tank. With this function must with an arrangement after 1b the filter load is taken into account.

Is the pre-filter 20 loaded, at higher outside temperatures, the fuel through the pre-filter 20 relaxed, causing gas bubbles, which then the electric fuel pump 34 sucks. The gas bubbles are through the electric fuel pump 34 compressed again, or excreted by a conventional degassing. However, the impeller rotates at a higher speed and lower load. If power failures occur during operation, an error entry in Tanksteuerge advises 28 respectively. If the break-ins are so great that even pressure drops occur, this is a simple error diagnosis of the loading condition of the prefilter 20 possible.

Will the electric fuel pump 34 controlled in normal operation and a filter load detected, can also be a worn electric fuel pump 34 or a coked collector of the drive motor of the electric fuel pump 34 available. Will the electric fuel pump 34 brought to speed by full load and then again higher efficiencies achieved, was a Teilverkokung before, which was burned by the speed increase again. If a given characteristic of voltage over current is exceeded with poor efficiency, there is also coking or a worn collector.

Claims (9)

Method for detecting a fault condition of a fuel delivery system for supplying an internal combustion engine ( 30 ), with a fuel filter ( 34 ) and at least one electric fuel pump ( 34 ), characterized in that a hydraulic power (P _hyd ) in the fuel system and an electric power (P _el ) of the electric fuel pump ( 34 ) are compared with each other and an error state is derived when deviating from predetermined values and / or exceeding or falling below predetermined threshold values. A method according to claim 1, characterized in that an impermissible loading condition of the fuel filter ( 32 ) and / or is detected when an efficiency (η), which is formed from hydraulic and electrical power (P _hyd , P _el ), falls below a predetermined threshold. A method according to claim 2, characterized in that for the evaluation of a correction with respect to a pulse width modulated modulated signal for controlling the electric fuel pump ( 34 ) is carried out. Method according to one of the preceding claims, characterized in that upon supply of electrical power (P _el ) and sudden collapse or lack of construction of the hydraulic power (P _hyd ) is detected on a line _break . Method according to one of the preceding claims, characterized in that during deceleration phases of the internal combustion engine ( 30 ) with vanishing hydraulic power (P _hyd ) the supplied electric power (P _el ) is compared with two threshold values. A method according to claim 5, characterized in that falls below the lower threshold, a closure of one or more ejector pumps ( 16 . 18 ) of the fuel system is detected. Method according to claim 5 or 6, characterized that when crossing an upper threshold leakage in the fuel delivery system is recognized. Method according to one of the preceding claims, characterized in that in case of power cuts during operation of the electric fuel pump ( 34 ) with simultaneous pressure drops, a loading of a prefilter ( 20 ) of the fuel pump is detected. Method according to one of the preceding claims, characterized in that, if in poor efficiency (η) exceeded a limit characteristic of a voltage curve (U) above the current (I), a coking and / or a spent collector of the electric fuel pump ( 34 ) is recognized.