Fuel supply device for engine injection and exhaust-gas after treatment

Abstract

A fuel supply device (2), in particular for use in a motor vehicle comprising an internal combustion engine (20), has a fuel supply pump (4) which is designed to remove fuel (28) from a fuel tank (6) and to release said fuel under increased pressure through an outlet; a first fluid connection (7) which is provided for connecting an exhaust line metering device (8) and; a second fluid connection (10) which is provided for connecting an engine injection device (12). The first fluid connection (7) is directly connected to the outlet of the fuel supply pump (4). A fluid choke (16) is arranged between the outlet of the fuel supply pump (4) and the second fluid connection (10). The invention enables an exhaust line metering device (8) and an engine injection device (12) to be operated reliably on a common fuel supply device (2).

Claims

1. A fuel supply device (2) comprising a controllable fuel delivery pump (4), which is configured to extract fuel (28) from a fuel tank (6) and to output said fuel at elevated pressure through an outlet, a first fluid port (7), which is configured for the connection of an exhaust-tract dosing apparatus (8), and a second fluid port (10), which is configured for the connection of an engine injection apparatus (12), wherein the first fluid port (7) is connected directly or via a fuel filter (9) to the outlet of the fuel delivery pump (4), wherein a fluid throttle (16) is arranged between the outlet of the fuel delivery pump (4) and the second fluid port (10), and wherein the fuel supply device (2) is configured to, during normal operation, set the delivery quantity of the controllable fuel delivery pump (4) such that a provided fuel quantity is sufficient to provide, at the second fluid port (10), a fuel quantity required by the engine injection apparatus (12), and in response to a regeneration operation, increase a delivery power of the fuel delivery pump (4) and activate the exhaust-tract dosing apparatus (8) connected to the first fluid port (7), in order to inject fuel into the exhaust tract (22).

2. The fuel supply device (2) as claimed in claim 1, wherein the inlet of an overflow valve (14) is connected to the second fluid port (10), which overflow valve allows excess fuel to be returned into the fuel tank (6).

3. The fuel supply device (2) as claimed in claim 2, wherein the overflow valve (14) is formed, at an inlet side, with an overflow valve filter element (13) or, at an outlet side, with an overflow valve throttle element (15).

4. The fuel supply device (2) as claimed in claim 1, wherein a fuel filter (9) is provided between the outlet of the fuel delivery pump (4) and the first fluid port (7) or between the outlet of the fuel delivery pump (4) and the fluid throttle (16).

5. The fuel supply device (2) as claimed in claim 1, wherein the fuel delivery pump (4) is controllable in continuously variable or electronic fashion.

6. A method for regenerating a particle filter (24) which is arranged in an exhaust tract (22) of an internal combustion engine (20) having a fuel supply device (2) as claimed in claim 1, and the exhaust-tract dosing apparatus (8) which is connected to the first fluid port (7) and which is configured to inject fuel (28), which is provided by the fuel supply device (2), upstream of the particle filter (24) in the exhaust tract (22) of the internal combustion engine (20), wherein the method comprises: (a) increasing a delivery power of the fuel delivery pump (4); and (b) injecting a desired quantity of fuel (28) into the exhaust tract (22) by operating the exhaust-tract dosing apparatus (8).

7. The method as claimed in claim 6, wherein the method comprises operating the fuel delivery pump (4) with a maximum power.

8. A method for operating an internal combustion engine (20) having a fuel supply device (2) as claimed in claim 1, and an engine injection apparatus (12) which is connected to the second fluid port (10) and which is configured to inject fuel (28) into at least one combustion chamber (30) of the internal combustion engine (20), wherein the method comprises: setting a delivery quantity of the fuel delivery pump (4) such that the engine injection apparatus (12) is provided with a sufficient fuel quantity.

9. The method as claimed in claim 8, wherein the method comprises setting the delivery quantity of the fuel delivery pump (4) such that the engine injection apparatus (12) is provided with a fuel quantity which is greater than a fuel quantity required by the engine injection apparatus (12).

10. The method as claimed in claim 8, wherein the method comprises discharging excess fuel (28) by opening an overflow valve (14) upstream of the engine injection apparatus (12).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An exemplary embodiment of the invention will be discussed in more detail below on the basis of the appended figures, in which:

(2) FIG. 1 is a schematic illustration of a system for injecting fuel into an exhaust tract of an internal combustion engine;

(3) FIG. 2 is a schematic illustration of a fuel supply device according to an exemplary embodiment of the invention; and

(4) FIG. 3 schematically shows an example of a characteristic curve of an overflow valve as is used in a fuel supply device according to an exemplary embodiment of the invention.

DETAILED DESCRIPTION

(5) FIG. 1 shows a system for injecting fuel into an exhaust tract 22 of an internal combustion engine 20 in a schematic illustration.

(6) An exhaust-tract dosing apparatus 8 is mounted on the exhaust tract 22 between the internal combustion engine 20 and a particle filter 24 arranged downstream of the internal combustion engine 20. By means of a fuel supply device 2, fuel 28 is extracted from a fuel tank 6 via a fuel line 3 and is fed to the exhaust-tract dosing apparatus 8.

(7) The exhaust-tract dosing apparatus 8 is designed to inject a desired fuel quantity into the exhaust tract 22. In the exhaust tract 22, the injected fuel 28 mixes with the exhaust gases 26 flowing through the exhaust tract 22 and ignites, in particular on an oxidation catalytic converter 23 arranged between the exhaust-tract dosing apparatus 8 and the particle filter 24.

(8) The high temperatures that arise in the exhaust tract 22 during the combustion of the injected fuel 28 cause particles, in particular soot particles, that have previously collected in the particle filter 24 to be burned off, and the particle filter 24 to be regenerated.

(9) The fuel supply device 2 also supplies fuel 28 to an engine injection apparatus 12. The fuel 28 is injected by the engine injection apparatus 12 into the combustion chambers (cylinders) 30 of the engine 20.

(10) The fuel supply device 2 also comprises a fuel return line 17 which allows excess fuel 28 to be returned into the fuel tank 6.

(11) The construction and function of the fuel supply device 2 will be discussed in more detail below on the basis of the enlarged illustration shown in FIG. 2.

(12) The fuel supply device 2 comprises a fuel delivery pump 4, which is designed to extract fuel 28 from the fuel tank 6 through the fuel line 3 and to feed said fuel at elevated pressure to a first fluid port 7 through a pressure line 5, in which a fuel filter 9 is arranged. The first fluid port 7 is provided for the connection of the exhaust-tract dosing apparatus 8.

(13) Via a fluid throttle 16, the pressure line 5 is also connected to a second fluid port 10, which is provided for the connection of an engine injection apparatus 12.

(14) Downstream of the fluid throttle 16, that is to say on that side of the fluid throttle 16 which is averted from the pressure line 5, there is situated an overflow valve 14, which is connected at the outlet side to the fuel return line 17. By virtue of the overflow valve 14 being opened, excess fuel 28 can be returned into the fuel tank 6.

(15) The overflow valve 14 is formed, at the inlet side, with an overflow valve filter element 13 and/or, at the outlet side, with an overflow valve throttle element 15. By means of a filter element 13 which is arranged upstream of the overflow valve 14, a blockage of the overflow valve 14 by foreign bodies and/or contaminants can be reliably prevented.

(16) The overflow valve 14 comprises in particular a spring-piston element 14a, which is designed such that the overflow valve 14 has a steep characteristic curve at a predefined operating point. By means of the construction of the overflow valve 14 with a spring-piston element 14a and with an overflow valve throttle element 15 which is arranged downstream of the overflow valve 14, the pressure that prevails at the second fluid port 10 can be controlled and/or limited.

(17) The filter element 13, the overflow valve 14 and the overflow valve throttle element 15 are, in FIG. 2, illustrated as constituent parts of the fuel supply device 2. Alternatively, the filter element 13, the overflow valve 14 and the overflow valve throttle element 15 may also be formed within the engine injection apparatus 12.

(18) During the normal operation of the internal combustion engine 20, when no regeneration of the particle filter 24 is taking place, the exhaust-tract dosing apparatus 8 connected to the first fluid port 7 is deactivated. During normal operation, the delivery quantity of the fuel delivery pump 4 is set such that the provided fuel quantity is sufficient to set the desired or required fuel pressure at the inlet of the engine injection apparatus 12, which is connected to the second fluid port 10, by means of the interaction of the overflow valve 14 and the overflow valve throttle element 15.

(19) For effective operation of the internal combustion engine 20 and of the fuel supply device 2, the delivery quantity of the fuel delivery pump 4 is in particular set such that the fuel quantity provided by the fuel supply device 2 at the second fluid port 10 is not significantly greater than the quantity of fuel 28 injected by the engine injection apparatus 12 into the combustion chambers 30 of the engine 20.

(20) To maintain a constant pressure at the inlet of the engine injection apparatus 12 and to prevent excessive pressure fluctuations, the fuel quantity provided at the second fluid port 10 must be slightly greater than the fuel quantity injected into the combustion chambers 30 of the engine 20. A part of the fuel is also required for the cooling of the engine injection apparatus 12. Excess fuel 28 that is not required by the engine injection apparatus 12 is returned into the fuel tank 6 through the opened overflow valve 14 and the fuel return line 17.

(21) To regenerate the particle filter 24 (regeneration operation), the delivery power of the fuel delivery pump 4 is increased, and the exhaust-tract dosing apparatus 8 connected to the first fluid port 7 is activated in order to inject the desired/required quantity of fuel 28 into the exhaust tract 22.

(22) The fluid throttle 16 makes it possible to set a higher pressure at the inlet of the exhaust-tract dosing apparatus 8 connected to the first fluid port 7 than at the engine injection apparatus 12 connected to the second fluid port 10. In this way, the exhaust-tract dosing apparatus 8 can be operated reliably without the need for the engine injection apparatus 12 to be operated with an excessively high fuel pressure. The fuel pressure prevailing at the first fluid port 7 may for example amount to 4.4 to 8.9 bar, and the fuel pressure prevailing at the second fluid port may for example amount to between 3.5 and 4.0 bar, in particular 3.8 bar.

(23) FIG. 3 shows a characteristic curve of the overflow valve 14 in a schematic illustration.

(24) Here, the pressure difference p between the inlet and the outlet of the overflow valve 14 is plotted on the horizontal axis (x axis). The throughflow quantity Q through the overflow valve 14 is plotted on the vertical axis (y axis).

(25) For small pressure differences p<p.sub.min, the overflow valve 14 has a very shallow characteristic curve, such that the overflow valve 14 is practically closed in said range. In the range p>p.sub.min, the overflow valve 14 has a very steep characteristic curve of for example 400 l/h/bar. The operating point p.sub.0 of the engine injection apparatus 12, which lies for example between 3.5 and 4.0 bar, in particular at 3.8 bar, is situated in the steep region of the characteristic curve. In this way, pressure fluctuations are absorbed by the overflow valve 14, and a highly constant pressure around the operating point p.sub.0 is provided at the inlet of the engine injection apparatus 12, which is connected to the second fluid port 10 of the fuel supply device 2.

(26) The overflow valve 14 makes it possible for the pressure at the second fluid port 10 or at the engine injection apparatus 12 to remain virtually constant about a predefined target value (operating point p.sub.0) that permits correct functioning of the engine injection apparatus 12.

(27) The fluid throttle 16 makes it possible for fuel at elevated pressure to be provided at the first fluid port 7, or at the exhaust-tract dosing apparatus 8, without the pressure at the second fluid port 10 exceeding the predefined target value.

(28) The invention thus makes it possible for an exhaust-tract dosing apparatus 8 and an engine injection apparatus 12 to be operated reliably on a common fuel supply device 2. It is thus possible to dispense with an additional fuel supply device 2 for supplying the exhaust-tract dosing apparatus 8. In this way, the production outlay and the production costs can be considerably reduced.