WO2009152876A1

WO2009152876A1 - Fuel supply device

Info

Publication number: WO2009152876A1
Application number: PCT/EP2008/066786
Authority: WO
Inventors: Werner Hess; Alexander Schenck Zu Schweinsberg; Udo Sieber; Uwe Kassner
Original assignee: Robert Bosch Gmbh
Priority date: 2008-06-17
Filing date: 2008-12-04
Publication date: 2009-12-23
Also published as: DE102008002462A1

Abstract

The invention relates to a fuel supply device for an internal combustion engine (10) in a motor vehicle, comprising a fuel tank (11), an electric fuel pump (12) for delivering fuel to a fuel line (13), an accumulator (18), and an electronic control unit (24) controlling the fuel pump (12) as a function of the pressure in the fuel line (13), such that it switches off when an upper pressure threshold is exceed, and is switched on when said pressure drops below a lower pressure threshold. In order to reduce fuel consumption, the control unit (24) also switches the fuel pump (12) on whenever the internal combustion engine (10) is in coasting mode and the pressure in the fuel line (13) falls below the upper pressure threshold.

Description

description

Title fuel supply device

State of the art

The invention relates to a fuel supply device for an internal combustion engine in a motor vehicle according to the preamble of claim 1.

A known fuel supply device for an internal combustion engine or an internal combustion engine (US Pat. No. 5,701,869, FIG. 10) has a fuel pump arranged in the fuel tank, which conveys fuel from the fuel tank via a check valve into a fuel supply line leading to the internal combustion engine. To the fuel supply line designed as a spring accumulator pressure accumulator and the pressure in the fuel supply line measuring pressure sensor is connected. An electronic control unit connected on the input side to the pressure sensor controls the fuel pump in such a manner that the fuel pump is switched off at a pressure which is equal to or greater than a predetermined upper pressure threshold and the pressure accumulator alone supplies fuel to the internal combustion engine and after the pressure has dropped or below a predetermined lower pressure threshold, which is measured at largely empty accumulator, is turned on again, so that fuel from the fuel tank to

Pressure accumulator and pumped to the internal combustion engine. The intermittent activation of the fuel pump has the advantage that the power consumption of the pump can be reduced overall.

Disclosure of the invention

The fuel supply device according to the invention with the features of claim 1 has the advantage that the energy demand of the fuel pump is largely covered during the overrun operation of the internal combustion engine, in which the pump current without additional consumption of fuel is available and is now used according to the invention to stretch the pressure accumulator to an upper pressure threshold, in which the fuel pump is switched off to reduce the power consumption. By choosing the operating phases in which the internal combustion engine operates in overrun mode, for charging or filling the accumulator, a significant fuel consumption savings is achieved.

The measures listed in the further claims advantageous refinements and improvements of the claim 1 fuel supply device are possible.

According to an advantageous embodiment of the invention, the control of the fuel pump by the control unit is set in such a way that the shutdown of the fuel pump takes place when the fuel pressure in the fuel line reaches or exceeds a predetermined upper pressure threshold and the switching on of the fuel pump then takes place Pushing operation of the internal combustion engine is present and the fuel pressure in the fuel supply below the upper pressure threshold, preferably at least by a predetermined amount below the upper

Pressure threshold, drops or the fuel pressure in the fuel supply line drops to or below a predetermined lower pressure threshold. The provision of a minimum amount by which the fuel pressure must drop below the upper pressure threshold in coasting operation, so that the fuel pump is turned on, allows a defined, stable operation of the fuel pump and prevents their flutterartiges, constant switching on and off.

According to an advantageous embodiment of the invention, the pressure accumulator is arranged between the fuel pump and the fuel supply line and the accumulator is preceded by a first valve opening in the conveying direction and a downstream closed at standstill of the internal combustion engine second valve. The first valve, preferably one

Check valve is prevented when switching off the fuel pump, a backflow of the fuel to the fuel pump and the second valve ensures when switching off the engine, that the pressure in the accumulator is maintained, which contributes to an improved starting behavior of the internal combustion engine. The second valve may be a shut-off valve controlled by an engine control unit that is kept open during engine operation, but may also be designed as a 3/2-way valve to maintain the pressure in the accumulator while the engine is stopped, but to depressurize the fuel supply line to get. Brief description of the drawings

The invention is explained in more detail in the following description with reference to an exemplary embodiment shown in the drawings. Show it:

1 is a block diagram of a fuel supply device for an internal combustion engine of a motor vehicle,

2 shows an alternative exemplary embodiment of a hydraulic accumulator downstream of a pressure accumulator of the fuel supply device according to FIG. 1 in the conveying direction, FIG.

Fig. 3 shows a detail of a diagram of the pressure curve in the fuel supply line

Fuel supply device according to FIG. 1 in association with a diagram of the vehicle speed over time at a prescribed European exhaust gas test.

The fuel supply device shown in FIG. 1 for an internal combustion engine 10 of a motor vehicle has a fuel tank 11 that can be filled with fuel and a fuel pump 12 that delivers fuel from the fuel tank 11 into a fuel supply line 13. at

Internal combustion engines with direct fuel injection, a high-pressure pump 14 is connected to the fuel supply line 13, which supplies a fuel distributor 15 with fuel under high pressure. In turn, fuel injection valves or injectors 16, via which fuel is injected into combustion cylinders of internal combustion engine 10, are connected to fuel distributor 15. In internal combustion engines with intake manifold injection eliminates the high-pressure pump and the fuel is injected via fuel injection valves in the leading to the combustion cylinders suction pipes. An engine control unit 17 takes over the control and regulation of the injection and other engine functions. Between the fuel pump 12 and the fuel supply line 13, a pressure accumulator 18 is arranged, which is connected upstream of a first valve 19 and a second valve 20 downstream, in each case seen in the conveying direction of the fuel pump. The pressure accumulator 18 may be formed, for example, as a gas pressure accumulator or as a spring accumulator. Fuel pump 12, pressure accumulator 18 and the two valves 19, 20 are preferably arranged in the fuel tank 11. The first valve 19 opens exclusively in the conveying direction and is preferably as Check valve executed. In the exemplary embodiment of FIG. 1, the second valve 20 is a shut-off valve 21 which is actuated by the engine control unit 17 via a control signal line 26 and which is open during operation of the internal combustion engine 10 and closes when the internal combustion engine 10 is turned off. The first valve 19 prevents fuel from the pressure accumulator 18 flows back to the fuel pump 12 when the fuel pump 12 is turned off. When switching off the internal combustion engine 10, the second valve 20 closes off the pressure accumulator 18 on the output side, so that the fuel pressure in the pressure accumulator 18 is maintained.

2, an alternative embodiment of the first valve 19 is shown. The first valve 19 is designed here as a 3/2-way solenoid valve 22 with three controlled connections, which is controlled via the control signal line 27 from the engine control unit 17. Of the three controlled ports, a first port 221 is connected to the fuel supply line 13, a second port 222 is connected to the output of the accumulator 18, and a third port 223 is connected to a return 23 to the fuel tank 11. When the internal combustion engine 10 is turned off, the 3/2-way solenoid valve 22 is in its basic position, in which the pressure accumulator 18 is shut off via the second port 222 and the fuel supply line 13 is connected to the return 23 via the first port 221 and the third port 223 , At standstill of the internal combustion engine 10, the pressure in the pressure accumulator 18 is thus maintained and the fuel supply line 13 is depressurized via the return line 23. When starting the internal combustion engine 10, the engine control unit 17 switches the 3/2-way solenoid valve 22 in its working position, in which

Pressure accumulator 18 and fuel supply line 13 via the first and second ports 221 and 222 are interconnected and the return 23 is shut off via the third port 223.

The fuel pump 12 is temporarily switched on and off depending on the pressure in the fuel supply line 13 by means of an integrated in the engine control unit 17, electronic control unit 24. In the embodiment of FIG. 1, the fuel pressure is measured by means of a pressure sensor 25 or pressure sensor connected to the fuel supply line 13, which sends an electrical signal corresponding to the measured value via the signal line 26 to the control unit 24. Instead of a pressure sensor 25, the fuel pressure can be modeled in the engine control unit 17.

During engine operation, when the second valve 20 is permanently open, the fuel pump 12 is controlled by the control unit 24 so that it is switched off when reaching or exceeding an upper pressure threshold p _{0 of} the fuel pressure in the fuel supply line 13, at which the pressure accumulator 18 has its maximum filling pressure and after the fuel pressure has dropped in the fuel supply line 13 at or below a lower pressure threshold p _u for filling or recharging the accumulator 18 is turned on again. By way of example, the upper pressure threshold p ₀ = 6 bar and the lower pressure threshold p _u = 4 bar. In addition, to fill the pressure accumulator 18 primarily operating phases of the internal combustion engine 10, in which it operates in overrun, used by the fuel pump 12 is then turned on in each phase of the overrun, when the fuel pressure in the fuel supply line 13 drops below the upper pressure threshold p ₀ more precisely, at least by a predetermined amount Δp is smaller than the upper pressure threshold p ₀ , that is, the pressure in the fuel supply line 13 reaches or falls below a lower than the upper pressure threshold p ₀ by Δp mean pressure threshold p _m . In this way, the energy available to the pump flow in the overrun mode of the internal combustion engine 10 without additional fuel consumption is used to recharge the pressure accumulator 18 to its maximum pressure. The pressure thresholds p ₀ , p _m and p _u are stored in the control unit 24 and the overrun operation is sensed in the engine control unit 17 and a corresponding thrust signal to the control unit 24.

FIG. 3 shows a graph of the course of the pressure p in the fuel supply line 13 in association with a plurality of consecutive vehicle speed cycles when a European exhaust gas test is carried out. During the exhaust test, the vehicle is accelerated in several cycles to a certain speed and then again reduces the vehicle speed to zero. By way of example, in three repetitive cycles Z1, Z2, Z3, the vehicle is first accelerated to 15 km / h or to 32 km / h or to 50 km / h and then the vehicle speed is again reduced to zero. In cycle Z3, the vehicle speed is kept constant for a short time at 35 km / h during the speed reduction. The time interval occurring in each cycle, in which the internal combustion engine 10 is in coasting mode, is indicated in the lower diagram of FIG. 3 as a coasting phase t _s . During the coasting phase t _s in the first cycle Zl, the fuel pressure p in the fuel supply line 13 is still above the mean pressure threshold p _m , while in the overrun phase t _s in the second cycle Z2, the pressure p has dropped to the mean pressure threshold p _m and the Control unit 24, the fuel pump 12 turns on again, which in turn raises the pressure by pumping fuel from the fuel tank 11 into the pressure accumulator 18 to the upper pressure threshold p ₀ . If the upper pressure threshold p _{0 is} reached, the fuel pump 12 is switched off again. During the further operation of the internal combustion engine 10, the pressure p in the fuel supply line 13 decreases again, and falls only in the overrun phase t _s im Cycle Z5 again below the mean pressure threshold p _m . The fuel pump 12 is turned on, and by conveying fuel, the pressure p in the fuel supply line 13 is raised again to the level of the upper pressure threshold p ₀ . A further switching on of the fuel pump 12 takes place in each case in the overrun phase t _s in the cycle Z8 and in the cycle Zl 1. When overrun in the cycle Zl 2 occurs (overrun t _s) , the fuel pressure p is still above the middle

Pressure threshold p _m , so that switching on the fuel pump 12 is omitted. The fuel pressure p in the fuel supply line 13 continues to drop, and when the next overrun phase t _{s occurs} in the cycle Zl 3, it has fallen significantly below the mean pressure threshold p _m . The fuel pump 12 is turned on and the accumulator 18 is biased back to maximum pressure p ₀ . In the further course of the cycle Zl 3, the fuel pressure p continues to drop, since switching off the fuel pump 12 is omitted due to a lack of overrun operation. The pressure p in the fuel supply line 13 drops very close to the lower pressure threshold p _u , but does not reach it, because with the end of cycle Zl 3 of the internal combustion engine 10 is operating in overrun mode and thus the control unit 24, the fuel pump 12 turns back on until it is switched off again when the upper pressure threshold p ₀ is reached.

Claims

claims

1. Fuel supply device for an internal combustion engine (10) in a motor vehicle, with a fuel tank (11), an electric fuel pump (12), the fuel from the

Fuel tank (11) in a fuel supply line (13) calls, with a fuel flow arranged in the pressure accumulator (18) and with a fuel pump (12) controlling electronic control unit (24) depending on the pressure in the fuel supply line (13), the fuel pump (12 ) to fill the pressure accumulator (18) turns on and off when the accumulator (19) is filled, characterized in that for filling the pressure accumulator

(18) phases (t _s ) of the overrun operation of the internal combustion engine (10) can be used.

2. Fuel supply device according to claim 1, characterized in that the shutdown of the fuel pump (12) takes place as soon as the pressure (p) in the fuel supply line (13) reaches or exceeds a predetermined upper pressure threshold (p ₀ ), and the switching on of the fuel pump ( 12) takes place as soon as overrun is present and the pressure (p) in the fuel supply line (13) drops below the upper pressure threshold (p ₀ ), preferably at least by a predetermined amount (Δp) below the upper pressure threshold (p ₀ ) or the pressure ( p) drops in the fuel supply line (13) to a predetermined lower pressure threshold (p _u ) or falls below this.

3. Fuel supply device according to claim 1 or 2, characterized in that in the fuel supply line (13) connected to the control unit (24) pressure sensor (25) is arranged, the one the measured pressure (p) in the fuel supply line (13) proportional electrical Output signal to the control unit (24).

4. Fuel supply device according to one of claims 1 to 3, characterized in that the pressure accumulator (18) between the fuel pump (12) and fuel supply line (13) is arranged, that the pressure accumulator (18) in the fuel flow stream only in the conveying direction opening first valve (19 ) and a closed at the standstill of the internal combustion engine (12) second valve (21) is connected downstream.

5. Fuel supply device according to claim 4, characterized in that the first valve (19) is a check valve with the fuel pump (12) facing the reverse direction.

6. Fuel supply device according to claim 4 or 5, characterized in that the second valve (20) during the operation of the internal combustion engine (10) controlled shut-off valve (21).

7. Fuel supply device according to claim 4 or 5, characterized in that the second valve (20) is a 3/2-way solenoid valve (22) with three controlled connections (221, 222, 223), of which a first connection (221 ) is connected to the fuel supply line (13), a second connection (222) to the outlet of the pressure accumulator (18) and a third connection (223) to a return line (23) leading to the fuel tank (11);

3/2-way solenoid valve (22) is switched during operation of the internal combustion engine (10) in its working position, in which the first terminal (221) connected to the second terminal (222) and the third terminal (223) is shut off, and with switching off of the internal combustion engine (10) falls back into its rest position, in which the first terminal (221) connected to the third terminal (223) and the second terminal (222) is shut off.

8. Fuel supply device according to one of claims 4 to 7, characterized in that the fuel pump (12) and at least the pressure accumulator (18), preferably also the two valves (19, 20) in the fuel tank (11) are arranged.