DE102018007473A1 - Method for operating a fuel pump and a corresponding fuel supply - Google Patents

Abstract

The disclosure relates to a method for operating a fuel pump that is part of a fuel supply of an internal combustion engine, the method comprising the following steps: • detecting a start time of an overrun operation during which the internal combustion engine is being towed, • deactivating the fuel pump until the end of the overrun operation at a termination time and • activating the fuel pump at the termination time.

Description

Technical field

The disclosure relates to methods of operating fuel pumps configured to deliver fuel from a fuel tank to an internal combustion engine of a motor vehicle. Furthermore, the disclosure relates to a fuel supply for a motor vehicle. When the internal combustion engine is ready, fuel pumps continuously deliver fuel to the internal combustion engine. Excess, i.e. Fuel that is not required by the internal combustion engine is conveyed back into the fuel tank. At least one disadvantage is that losses occur in the fuel supply, because at least partially more fuel is pumped than is actually required.

description

The object of the invention is to provide a method for operating a fuel pump, with which an energy consumption for operating the fuel pump can be reduced, and an associated fuel supply.

This object is achieved with the features of claim 1 and with a fuel supply according to claim 6. Further aspects are the subject 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 Startzeitpunkts eines Schubbetriebs, während dessen die Brennkraftmaschine geschleppt wird,
• • Deaktivieren der Kraftstoffpumpe bis zur Beendigung des Schubbetriebs zu einem Beendigungszeitpunkt, und
• • Aktivieren der Kraftstoffpumpe im Beendigungszeitpunkt.

Accordingly, a method is provided for operating a fuel pump that is part of a fuel supply for an internal combustion engine, the method comprising the following steps:

• Detection of a start time of an overrun operation during which the internal combustion engine is being towed,
• • Deactivating the fuel pump until the end of the overrun operation at a termination time, and
• • Activate the fuel pump at the time of termination.

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 which the fuel pump detects when the overrun fuel cut-off is detected DFCO , which can last from a start time to a completion time and during which the internal combustion engine is being dragged, out of operation.

Deactivating the fuel pump does not provide energy when no fuel is required. This saves electrical energy, which results in reduced CO2 emissions. This also eliminates a noise that emits an activated fuel pump and that can penetrate into an interior when the (quieter) internal combustion engine is towed.

The fuel pump can be electric, that is, it can have a drive motor that drives a pump. The pump draws fuel from the fuel tank and delivers it via a fluid-conducting fuel supply line to another part of the fuel supply close to the internal combustion engine. The fuel pump is typically located in close proximity to the fuel tank or, in some embodiments, within the fuel tank. In simple embodiments, the fuel pump can be operated in two operating modes, namely a deactivated mode with a delivery rate of 0 and a power supply of 0 volts and an activated mode with a constant delivery rate and constant power supply, for example of 12 volts. The delivery rate of the fuel pump can be controlled as required in more complex embodiments. The fuel pump can be operated by a separate control unit, which is its own, and / or by an engine control unit ( ECU ), which also controls and manages parts of the internal combustion engine. In one embodiment, the fuel pump can deliver fuel into the immediate vicinity of the internal combustion engine via supply lines, 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 generally draws little or no fuel). The fuel return line is connected to the fuel tank in a fluid-conducting manner.

Some engine control units (ECUs) for vehicles have program modules that detect towing and meanwhile a so-called overrun cut-off ( DFCO ) can perform. As a rule, at least one fuel supply is interrupted during overrun fuel cutoff because the demand volume flow becomes 0 l / min. This is taken into account, for example, by keeping the injection valves closed. During the fuel cut-off, further, in Individual units of the internal combustion engine and auxiliary units, for example camshaft adjusters, valve lift adjusters, water pumps, generators, charging devices (turbochargers and compressors) and the like, which are not described further, can be deactivated and / or controlled differently.

In one embodiment, a delivery rate of the fuel pump is regulated as a function of a required volume flow of fuel that the internal combustion engine requires. The delivery rate is set via the electrical current supplied to the fuel pump. The current can be emitted 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 reactivated when a clutch, via which the internal combustion engine can be connected to a transmission, is disengaged. It must be assumed that the internal combustion engine, separated from the drive train, does not have sufficient rotational inertia to continue running for a long time in towing mode. To prevent the internal combustion engine from coming to a standstill after disengaging, the fuel pump is accordingly reactivated 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, it is to be avoided that the internal combustion engine goes out or the speed drops so far that the internal combustion engine has to be started again and only has to be started up again by a starting 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 time of a coasting operation during which the internal combustion engine is being towed, and
• Means for deactivating the fuel pump until the end of the overrun operation at a termination time, and
• • Means for activating the fuel pump at the time of termination.

Furthermore, a device is provided with means which, in overrun mode, have an overrun cutoff ( 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 required volume flow of fuel which the internal combustion engine requires.

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

In one embodiment, one or more, in particular all, steps of the method can be carried out fully or partially in an automated manner, in particular by the control 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 illustration purposes only and are not intended to limit the scope of the present disclosure in any way. Show it:

• 1 schematically shows a floor plan of a motor vehicle with an internal combustion engine, a fuel tank and a fuel pump,
• 2nd 1 shows a flow idagram of a method which can be implemented in an engine control unit in order to control and regulate elements and components of the motor vehicle,
• 3rd a time course of a volume flow delivered by the fuel pump, and
• 4th a time course 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 designate similar elements. It should be appreciated that steps within a method can be performed in a different order without changing the principles of the present disclosure.

1 schematically shows a top view of a motor vehicle 1 , having an internal combustion engine 2nd , which is designed via a clutch 3rd with a gear 4th to be connected to drive wheels 5 to drive. Conversely, the internal combustion engine 2nd with clutch closed 3rd and with the vehicle in motion 1 the internal combustion engine 2nd be towed.

Parts of a fuel supply 6 are designed to use an engine control unit ECU to be controlled. For this purpose, the motor vehicle 1 an electrical subsystem 7 on, the signal lines shown in dashed lines 9 includes. The fuel supply 6 has a fuel pump 8th on that is fluid-conducting with a fuel tank 10th connected is. The fuel pump 8th can via a fuel supply line 11 a pump volume flow Vp of fuel from the fuel tank 10th to a suction area 15 a high pressure pump 12th promote. From the high pressure pump 12th back flow not required Vr runs via a fuel return line 13 back into the fuel tank 10th . This may only take place after a maximum pressure is exceeded, which is set via a pressure relief valve, not shown. The pressure relief valve ensures that in the suction area 15 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 (not shown) and executable program modules. The electrical subsystem 7 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 2nd and fuel supply 6 , including a fuel pump 8th to manage and control.

One about the electrical subsystem 7 to the fuel pump 8th Electric current output can be used to adjust one of the fuel pumps 8th pump volume flow to be promoted Vp can be varied. Alternatively, the delivery rate Pk be regulated by pulse width modulation, in which current is intermittent to the fuel pump 8th is given. With an increase in funding 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 2nd driven, it puts additional pressure on fuel, so that this is via injectors 14 that in the internal combustion engine 2nd ongoing combustion process can be supplied. The injectors 14 are also about the electrical subsystem 7 from the engine control unit ECU targeted.

The suction area 15 is the area in the motor vehicle 1 from which the high pressure pump 12th Sucks fuel in and conducts fluid with injectors 14 associated high pressure area 19th promotes. The fuel pump represents an 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 injectors 14 connected, in an air intake area, not shown, immediately before intake valves, not shown, of the internal combustion engine 2nd , themselves in direct injection into combustion chambers, not shown. If necessary, the electric injection valves 14 electronically controlled so that it is from the high pressure pump 12th Inject the supplied, pressurized fuel into the intended area (in front of an inlet valve or with direct injection into the combustion chamber).

During a push operation ( DFCO ) is from the internal combustion engine 2nd no fuel needed. In a pushing operation ( DFCO ) the injectors 14 from the engine control unit ECU controlled so that the internal combustion engine 2nd no fuel is supplied. At the same time the fuel pump 8th controlled so that it also has a pump volume flow Vp of 0 l / min. With some internal combustion engines 2nd can possibly cool the high pressure pump 12th to be necessary.

The fuel supply 6 is by the engine control unit ECU which about the electrical subsystem 7 the fuel pump 8th and injectors 14 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 14 connected is. The high pressure pump 12th delivers from the fuel pump 8th provided fuel under increased pressure from the suction area 15 to the injectors 14 . The engine control unit ( ECU ) has program modules, which the fuel pump 8th at a detected overrun fuel cut-off DFCO that from a start time t1 up to a termination time t2 can continue and meanwhile the internal combustion engine 2nd is towed, put out of operation.

2nd schematically shows a process flow 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 2nd is being towed. This operating mode activates the fuel cut-off DFCO . During the overrun fuel cut-off 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, causing the motor vehicle 1 can be operated with lower energy consumption and thus with lower CO2 emissions. In a third step 18th the overrun operation is terminated and the fuel pump is activated 8th .

3rd shows an example of the time course of a demand volume flow Vb and one from the fuel pump 8th provided to the suction area 15 the high pressure pump 12th delivered pump volume flow Vp . The demand volume flow Vb is less than that of the fuel pump 8th provided pump volume flow Vp . It can be assumed that both moving parts, not shown, 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 is reached Vp is available. As a result, it takes a certain amount of time before there is a sudden need for power to the internal combustion engine 2nd and so that additional fuel requirement is sufficient fuel available. Through a slightly excess supply of fuel to the high pressure pump 12th can be achieved that sufficient fuel is always available. At a start time t1 in which a fuel cut-off DFCO is initiated, the demand volume flow Vb at 0 l / min. It will also be the fuel pump 8th deactivated or supplied with a current of 0 volts, their delivery rate Pk and the pump volume flow Vp become 0 l / min. In a termination time t2 the fuel cut-off DFCO completed. The fuel pump 8th is reactivated 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 3rd is separated and with an engine going out 2nd is to be expected.

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

Although at least one exemplary embodiment has been presented in the preceding description and the description of the figures, it should be recognized that a large number of variations exist. Furthermore, it should be recognized that the exemplary embodiment or exemplary embodiments are only examples and that they are not used to limit the scope of protection, the applicability or the precise configuration in any way. Rather, the description and the description of the figures provide the 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 described features can be carried out without leaving the scope of protection of the claims and their equivalents .

Reference list

1

Motor vehicle

2nd

Internal combustion engine

3rd

clutch

4th

transmission

5

Drive wheels

6

Fuel supply

7

electrical subsystem

8th

Fuel pump

9

Signal lines

10th

Fuel tank

11

Fuel supply line

12th

high pressure pump

13

Fuel return line

14

Injectors

15

Suction area

16

first step

17th

second step

18th

Third step

19th

High pressure area

DFCO

Push operation

ECU

Engine control unit

Pk

Delivery rate

U

rotational speed

Around

Minimum speed

Vb

Required volume flow

Vr

Return flow

Vp

Pump volume flow

Claims (10)

Method for operating a fuel pump (8) which is part of a fuel supply (6) for an internal combustion engine (2), the method comprising the following steps: • Detection of a start time (t1) of a coasting operation during which the internal combustion engine (2) is being towed, and • Deactivating the fuel pump (8) until the end of the overrun operation at a termination time (t2), and • Activate the fuel pump (8) at the time of termination (t2). Procedure according to Claim 1 , wherein in overrun mode an overrun cutoff (DFCO) takes place, 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. Procedure according to Claim 1 A delivery rate (Pk) of the fuel pump (8) is regulated as a function of a required volume flow (Vb) of fuel which the internal combustion engine (2) requires. Method according to one of the preceding claims, wherein the fuel pump (8) is reactivated 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 reactivated when the speed falls below a minimum (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), the engine control unit (ECU) having program modules, which Shut down the fuel pump (8) in the event of a detected overrun fuel cutoff (DFCO), which can last from a start time (t1) to a completion time (t2) and during which the internal combustion engine (2) is being towed. Fuel supply (6) after Claim 6 , During the overrun fuel cutoff (DFCO), a required volume flow (Vb) of fuel provided by the fuel supply (6) to the internal combustion engine (2) becomes 0 l / min. Fuel supply after Claim 6 and / or 7, a delivery rate (Pk) of the fuel pump (8) being regulated as a function of a required volume flow (Vb) of fuel which the internal combustion engine (2) requires. Fuel supply (6) according to one of the Claims 6 to 8th The fuel pump (8) is reactivated when a clutch (3) via which the internal combustion engine (2) can be connected to a transmission (4) is disengaged. Fuel supply (6) according to one of the claims, wherein the fuel pump (8) is reactivated when a minimum speed (Um) is undershot.

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