DE102018007473B4 - Method for operating a fuel pump and a corresponding fuel supply - Google Patents

Abstract

Method for operating a fuel pump (8) which is part of a fuel supply (6) of an internal combustion engine (2), a delivery rate (Pk) of the fuel pump (8) depending on a required volume flow (Vb) of fuel which the internal combustion engine (2) is required, is regulated and an unneeded return volume flow (Vr) runs via a fuel return line (13) back into a fuel tank (10), the method comprising the following steps: Detecting a start time (t1) of an overrun mode during which the internal combustion engine (2) is towed, whereby an overrun cut-off (DFCO) takes place in overrun mode, in which a required volume flow (Vb) of fuel to be provided by the fuel supply (6) to the internal combustion engine (2) becomes 0 l / min and • deactivation of the fuel pump ( 8) so that a pump volume flow (Vp) of the fuel pump (8) becomes 0 l / min, until the overrun is terminated at a termination point in time (t2 ), and • Activation of the fuel pump (8) at the termination time (t2), so that the pump volume flow (Vp) is again so high that at least the required volume flow (Vb) is covered.

Description

Technical area

The disclosure relates to a method for operating fuel pumps designed to deliver fuel from a fuel tank to an internal combustion engine of a motor vehicle. The disclosure also relates to a fuel supply for a motor vehicle. When the internal combustion engine is ready for operation, fuel pumps always deliver fuel to the internal combustion engine. Excess fuel, i.e. not required by the internal combustion engine, is pumped back into the fuel tank. At least one disadvantage is that there are losses in the fuel supply, because at least in part more fuel is pumped than is actually required.

the DE 100 61 855 A1 discloses a method, computer program and control and / or regulating device for operating an internal combustion engine. In this case, the fuel is pumped into a fuel line by a fuel pump. In order to be able to reliably detect a fuel leak, the fuel pressure in the closed fuel system is detected in a state of the internal combustion engine in which the fuel is not conveyed by the fuel pump and the fuel line is part of a closed fuel system. If the pressure in the closed fuel system drops by an amount which is above a limit value, a message is issued.

the DE 10 2011 077 249 A1 discloses a method and a controller for controlling a fuel injection system for an engine of a motor vehicle. The fuel injection system has a high-pressure pump in order to pressurize fuel delivered from a tank to a rail. It is proposed to throttle the supply of fuel to a high-pressure-generating pump element of the high-pressure pump as soon as a shutdown signal that the vehicle engine is to be shutdown is detected. For this purpose, for example, a metering device that throttles or closes a fuel flow to the pump elements. Alternatively, an electric fuel pump can be throttled or switched off. The inventive control of the fuel injection system prevents the high-pressure pump from running dry when the vehicle engine is restarted and the associated wear of the cams driven by the engine and the pistons of the pump elements resting on them
The invention is based on the object of providing a method for operating a fuel pump with which energy consumption for operating the fuel pump can be reduced, as well as an associated fuel supply.

This object is achieved with the features of claim 1 and with a fuel supply according to claim 4. Further aspects are in each case the subject matter of the subclaims, which can be combined with one another in a technologically meaningful manner. The description, in particular in connection with the figures, additionally characterizes and specifies the invention.

• Erfassen eines ein Startzeitpunkts eines Schubbetriebs, während dessen die Brennkraftmaschine geschleppt wird, wobei im Schubbetrieb eine Schubabschaltung erfolgt, in der ein von der Kraftstoffversorgung an die Brennkraftmaschine bereitzustellender Bedarfsvolumenstrom an Kraftstoff zu 0 l/min wird und
• • Deaktivieren der Kraftstoffpumpe so dass ein Pumpvolumenstrom der Kraftstoffpumpe zu 0 l/min wird, bis zur Beendigung des Schubbetriebs zu einem Beendigungszeitpunkt, und
• • Aktivieren der Kraftstoffpumpe im Beendigungszeitpunkt, so dass der Pumpvolumenstrom wieder so hoch ist, dass mindestens der Bedarfsvolumenstrom gedeckt ist.

Accordingly, a method is provided for operating a fuel pump that is part of a fuel supply to an internal combustion engine, a delivery rate of the fuel pump being regulated as a function of a volume flow of fuel required by the internal combustion engine, and an unneeded return flow flowing back into a fuel tank via a fuel return line , the method comprising the steps of:

• Detection of a starting point in time of an overrun mode during which the internal combustion engine is being towed, with an overrun shutdown taking place in which a required volume flow of fuel to be provided by the fuel supply to the internal combustion engine becomes 0 l / min and
• • Deactivating the fuel pump so that a pump volume flow of the fuel pump becomes 0 l / min, until the overrun operation is terminated at a termination point in time, and
• • Activation of the fuel pump at the time of termination so that the pump volume flow is again so high that at least the required volume flow is covered.

The fuel supply is controlled by the engine control unit, which can control the fuel pump and injection valves via the electrical subsystem. The engine control unit has program modules that control the fuel pump when an overrun fuel cut-off is detected DFCO , which can last from a starting time to an ending time and during which the internal combustion engine is towed, put out of operation.

Deactivating the fuel pump does not supply energy when fuel is not required. This saves electrical energy, which results in reduced CO2 emissions. This also eliminates the noise that an activated fuel pump emits and that can penetrate into an interior space when the internal combustion engine is dragged (quieter).

The fuel pump can be electric, that is to say it can have a drive motor that drives a pump. The pump sucks fuel from the fuel tank and conveys it via a fluid-conducting fuel supply line to a further part of the fuel supply close to the internal combustion engine. The fuel pump is usually arranged in close proximity to the fuel tank or, in some embodiments, within the fuel tank. The delivery rate of the fuel pump can be controlled as required. The fuel pump can be controlled by a separate control unit and / or by an engine control unit ( ECU ), which also controls and manages parts of the internal combustion engine, are controlled. In one embodiment, the fuel pump can deliver fuel via supply lines into the immediate vicinity of the internal combustion engine without a high-pressure pump, where it can be supplied directly to the internal combustion engine via injection valves. In an embodiment with a high-pressure pump, the fuel pump can also deliver fuel into a suction area of the high-pressure pump. Excess fuel that is not delivered to the internal combustion engine can escape into a fuel return line via a pressure relief valve which at a certain pressure (at which the high-pressure pump usually takes little or no fuel). The fuel return line is fluidly connected to the fuel tank.

Some engine control units (ECUs) for vehicles have program modules that record a towing operation and meanwhile a so-called overrun fuel cut-off ( DFCO ) This is taken into account by, for example, keeping injection valves closed. During the overrun fuel cut-off, other units of the internal combustion engine and ancillary units, such as camshaft adjusters, valve lift adjusters, water pumps, generators, charging devices (turbochargers and compressors) and the like, can be deactivated and / or otherwise controlled.

The delivery rate is adjusted via the electrical current supplied to the fuel pump. The current can be delivered intermittently by means of pulse width modulation in order to regulate the delivery rate. The delivery rate is proportional to the product of volume flow and pressure. When the delivery rate of the fuel pump increases, an increased volume flow is provided.

In one embodiment, the fuel pump is activated again when a clutch, via which the internal combustion engine can be connected to a transmission, is disengaged. It can be assumed that the internal combustion engine, separated from the drive train, does not have sufficient rotational inertia to continue to run for a long time in towing mode. In order to avoid the internal combustion engine coming to a standstill after the clutch has been disengaged, the fuel pump is accordingly activated again so that fuel is immediately available again when this is required.

In a further embodiment, the fuel pump is activated again when the speed falls below a minimum. According to this embodiment, too, the aim is to prevent the internal combustion engine from stalling or the speed dropping so far that the internal combustion engine has to be restarted and only has to be restarted by a start process via a starter and / or a combined starter / generator unit.

• • Mittel zum Erfassen eines ein Startzeitpunkts eines Schubbetriebs, während dessen die Brennkraftmaschine geschleppt wird, und
• • Mittel zum Deaktivieren der Kraftstoffpumpe bis zur Beendigung des Schubbetriebs zu einem Beendigungszeitpunkt, und
• • Mittel zum Aktivieren der Kraftstoffpumpe im Beendigungszeitpunkt.

Means are provided for operating a fuel pump, which is part of a fuel supply for an internal combustion engine, with:

• • Means for detecting a starting point in time of an overrun mode during which the internal combustion engine is being dragged, and
• • Means for deactivating the fuel pump until the overrun is terminated at a termination point in time, and
• • Means for activating the fuel pump at the time of termination.

Furthermore, a device is provided with means, which in the overrun mode, an overrun cut-off ( DFCO ), in which a required volume flow of fuel to be provided by the fuel supply to the internal combustion engine becomes 0 l / min.

Means are also provided which regulate a delivery rate of the fuel pump as a function of a volume flow of fuel required by the internal combustion engine.

Means are also provided which reactivate the fuel pump when a clutch, via which the internal combustion engine can be connected to a transmission, is disengaged.

In addition, means are provided which reactivate the fuel pump when the internal combustion engine falls below a minimum speed.

A means within the meaning of the present invention can be designed in terms of hardware and / or software, in particular a processing, in particular microprocessor unit (CPU) and / or a, preferably digital, processing unit (CPU) and / or a data or signal connected to a memory and / or bus system or several programs or Have program modules. The CPU can be designed to process commands which are implemented as a program stored in a memory system, to acquire input signals from a data bus and / or to output output signals to a data bus. A storage system can have one or more, in particular different, storage media, in particular optical, magnetic, solid and / or other non-volatile media. The program can be designed in such a way that it embodies or is able to execute the methods described here, so that the CPU can execute the steps of such methods and thus in particular control, in particular regulate, the actuator.

In one embodiment, one or more, in particular all, steps of the method can be carried out completely or partially in an automated manner, in particular by the controller or its means.

Figure list

• 1 schematisch einen Grundriss eines Kraftfahrzeugs mit einer Brennkraftmaschine, einem Kraftstofftank und einer Kraftstoffpumpe,
• 2 ein Flussidagramm eines Verfahrens, welches in einer Motorsteuereinheit implementiert sein kann, um Elemente und Bauteile des Kraftfahrzeuges zu steuern und zu regeln,
• 3 einen zeitlichen Verlauf eines von der Kraftstoffpumpe geförderten Volumenstroms, und
• 4 einen zeitlichen Verlauf einer Drehzahl einer Brennkraftmaschine.

The drawings described herein are for illustrative purposes only and are not intended to limit the scope of the present disclosure in any way. Show it:

• 1 schematically a floor plan of a motor vehicle with an internal combustion engine, a fuel tank and a fuel pump,
• 2 a flowchart of a method that can be implemented in an engine control unit in order to control and regulate elements and components of the motor vehicle,
• 3 a time profile of a volume flow delivered by the fuel pump, and
• 4th a time profile of a speed of an internal combustion engine.

The following description is merely illustrative in nature. For the sake of clarity, the same reference numbers are used in the drawings to identify similar elements. It should be noted that steps within a method can be performed out of the order without changing the principles of the present disclosure.

1 shows schematically in a plan view a motor vehicle 1 , comprising an internal combustion engine 2 , which is designed for this, via a coupling 3 with a gear 4th to be connected to drive wheels 5 to drive. Conversely, the internal combustion engine can 2 with the clutch closed 3 and when the vehicle is in motion 1 the internal combustion engine 2 be towed.

Parts of a fuel supply 6th are designed to have an engine control unit ECU to be controlled. For this purpose, the motor vehicle 1 an electrical subsystem 7th on, the signal lines shown in dashed lines 9 includes. The fuel supply 6th has a fuel pump 8th on that fluidly with a fuel tank 10 connected is. The fuel pump 8th can be via a fuel supply line 11 a pump volume flow Vp of fuel from the fuel tank 10 to a suction area 15th a high pressure pump 12th support financially. From the high pressure pump 12th return flow not required Vr runs through a fuel return line 13th back to the fuel tank 10 . If necessary, this only takes place after a maximum pressure has been exceeded, which is set via a pressure relief valve (not shown). The pressure relief valve ensures that in the suction area 15th a sufficient pressure level for the high pressure pump 12th is held.

The engine control unit ECU can have a computer and / or processor (not shown) and hardware, memory and executable program modules (not shown). The electrical subsystem 7th connects the engine control unit ECU with sensors, electrical connections etc. that are necessary to the operation of the vehicle 1 , including the internal combustion engine 2 and the fuel supply 6th , including a fuel pump 8th to manage and control.

One about the electrical subsystem 7th to the fuel pump 8th Electric current output can be used to set one of the fuel pump 8th pump volume flow to be conveyed Vp can be varied. Alternatively, the delivery rate Pk be regulated by a pulse width modulation, in the current intermittently to the fuel pump 8th is given. With an increase in a delivery rate Pk the fuel pump 8th becomes an increased pump volume flow Vp provided.

The high pressure pump 12th is, for example, mechanically via the internal combustion engine 2 driven, it additionally pressurizes fuel so that it flows through injection valves 14th that in the internal combustion engine 2 running combustion process can be fed. The injectors 14th are also via the electrical subsystem 7th from the engine control unit ECU targeted.

The suction area 15th is the area in the motor vehicle 1 , from which the high pressure pump 12th Sucks in fuel and transfers it to fluid-conducting with injection valves 14th connected high pressure area 19th promotes. The fuel pump represents the order of magnitude 8th a pressure of 0 to 10 bar ready. The high pressure pump 12th can provide pressures of 50 bar and more. The high pressure area 19th the high pressure pump 12th is fluid-conducting with injection valves 14th connected, which is in an air intake area, not shown, immediately in front of the intake valves, not shown, of the internal combustion engine 2 , open into combustion chambers (not shown) in the case of direct injection. If necessary, the electric injectors 14th electronically controlled so that they can be controlled by the high pressure pump 12th Inject the provided, pressurized fuel into the intended area (in front of an inlet valve or, in the case of direct injection, into the combustion chamber).

During overrun ( DFCO ) is from the internal combustion engine 2 no fuel required. In overrun mode ( DFCO ) are the injectors 14th from the engine control unit ECU controlled so that the internal combustion engine 2 no fuel is supplied. At the same time the fuel pump 8th controlled so that they also have a pump volume flow Vp of 0 l / min. In some internal combustion engines 2 can possibly cool the high pressure pump 12th to be necessary.

The fuel supply 6th is through the engine control unit ECU , which via the electrical subsystem 7th the fuel pump 8th and injectors 14th can control, controlled. The fuel pump 8th is with the high pressure pump 12th fluidly connected, the high pressure pump 12th fluid-conducting with the injection valves 14th connected is. The high pressure pump 12th promotes from the fuel pump 8th provided fuel under increased pressure from the suction area 15th to the injectors 14th . The engine control unit ( ECU ) has program modules that control the fuel pump 8th when an overrun fuel cut-off is detected DFCO , which can last from a start time t1 to a termination time t2 and during which the internal combustion engine 2 is towed, put out of service.

2 shows schematically a process sequence in the engine control unit ECU can be implemented to the fuel pump 8th to control. In a first step 16 it is detected that the motor vehicle 1 is in an operating mode in which the internal combustion engine 2 is towed. This operating mode activates the fuel cut-off DFCO . During the overrun fuel cutoff, in a second step 17th the fuel pump 8th deactivated. As a result, there is no avoidable electrical energy for driving the fuel pump 8th consumed, making the motor vehicle 1 can be operated with lower energy consumption and thus with lower CO2 emissions. In a third step 18th an end of the overrun mode is determined and the fuel pump is activated 8th .

3 shows an example of the time course of a required volume flow Vb as well as one from the fuel pump 8th provided to the suction area 15th the high pressure pump 12th delivered pump volume flow Vp . The demand volume flow Vb is less than that from the fuel pump 8th provided pump volume flow Vp . It can be assumed that both moving parts, not shown, are within the fuel pump 8th as well as the fuel to be delivered by it has an inertia and accordingly a desired pump volume flow is delayed when a setpoint value jump is reached Vp is available. As a result, it takes a certain amount of time before there is a sudden power requirement on the internal combustion engine 2 and thus sufficient fuel is available for additional fuel requirements. By providing a small excess of fuel to the high-pressure pump 12th it can be achieved that there is always enough fuel available. At a start time t1, in which an overrun fuel cut-off DFCO is initiated, the required volume flow Vb to 0 l / min. It then becomes the fuel pump as well 8th deactivated or supplied with a current of 0 volts, their delivery rate Pk and the pump volume flow Vp become 0 l / min. The overrun fuel cut-off is activated at a termination time t2 DFCO completed. The fuel pump 8th is activated again, so that the pump volume flow Vp is again so high that at least the required volume flow Vb is covered. The termination time t2 can occur when the clutch 3 is disconnected and with an engine shutdown 2 is to be expected.

As in 4th shown, activation of the fuel pump 8th be initiated that a speed U the internal combustion engine 2 a minimum speed Around falls below. The motor vehicle 1 means, not shown, for detecting a speed U the internal combustion engine 2 exhibit.

Although at least one exemplary embodiment was shown in the preceding description and the description of the figures, it should be recognized that there are a large number of variations. Furthermore, it should be recognized that the exemplary embodiment or the exemplary embodiments are only examples and that they do not serve to restrict the scope of protection, the applicability or the precise configuration in any way. Rather, the description and the description of the figures provide a person skilled in the art with useful instructions for implementing at least one embodiment; it should be clear that various changes in the form and function of the features described can be made without departing from the scope of protection of the claims and their equivalents .

List of reference symbols

1

Motor vehicle

2

Internal combustion engine

3rd

coupling

4th

transmission

5

Drive wheels

6th

Fuel supply

7th

electrical subsystem

8th

Fuel pump

9

Signal lines

10

Fuel tank

11

Fuel supply line

12th

high pressure pump

13th

Fuel return line

14th

Injectors

15th

Suction area

16

first step

17th

second step

18th

Third step

19th

High pressure area

DFCO

Overrun

ECU

Engine control unit

Pk

Delivery rate

U

rotational speed

Around

Minimum speed

Vb

Demand volume flow

Vr

Return flow

Vp

Pump volume flow

Claims (6)

Method for operating a fuel pump (8) which is part of a fuel supply (6) of an internal combustion engine (2), a delivery rate (Pk) of the fuel pump (8) depending on a required volume flow (Vb) of fuel which the internal combustion engine (2) is required, regulated and wherein a return volume flow (Vr) that is not required runs back into a fuel tank (10) via a fuel return line (13), the method comprising the following steps: • Detection of a starting time (t1) of an overrun operation during which the internal combustion engine (2) is being towed, with an overrun cut-off (DFCO) taking place in overrun, in which a required volume flow (Vb) to be provided by the fuel supply (6) to the internal combustion engine (2) of fuel becomes 0 l / min and • Deactivating the fuel pump (8) so that a pumping volume flow (Vp) of the fuel pump (8) becomes 0 l / min, until the end of the overrun mode at an end time (t2), and • Activation of the fuel pump (8) at the termination time (t2) so that the pump volume flow (Vp) is again so high that at least the required volume flow (Vb) is covered. Procedure according to Claim 1 , the fuel pump (8) being activated again when a clutch (3), via which the internal combustion engine (2) can be connected to a transmission (4), is disengaged. Method according to one of the preceding claims, wherein the fuel pump (8) is activated again when the speed falls below a minimum speed (Um). Fuel supply (6), which is partially controllable by an engine control unit (ECU), which can control a fuel pump (8) and injection valves (14) via an electrical subsystem (7), a delivery rate (Pk) of the fuel pump (8) depending on a demand volume flow (Vb) of fuel, which an internal combustion engine (2) requires, is regulated and with an unneeded return volume flow (Vr) running back into a fuel tank (10) via a fuel return line (13), the engine control unit (ECU) program- Has modules which put the fuel pump (8) out of operation in the event of a detected overrun fuel cut-off (DFCO), which can last from a start time (t1) to an end time (t2) and during which the internal combustion engine (2) is towed, so that a pump volume flow (Vp) of the fuel pump (8) becomes 0 l / min, the fuel pump (8) being activated again at the termination time (t2), so that the pump volume enstrom (Vp) is again so high that at least the required volume flow (Vb) of the internal combustion engine (2) is covered. Fuel supply (6) Claim 4 , the fuel pump (8) being activated again when a clutch (3), via which the internal combustion engine (2) can be connected to a transmission (4), is disengaged. Fuel supply (6) after one of the Claims 4 until 5 , whereby the fuel pump (8) is activated again when a minimum speed (Um) is undershot.

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