Fuel-pumping device for an internal combustion engine, and a method for pumping fuel in a fuel-pumping device

Abstract

The invention relates to a fuel-pumping device (1) for a fuel injection device of an internal combustion engine with a large high-pressure pump (16) and a small high-pressure pump (14) arranged in parallel, wherein fuel can be pumped by the large high-pressure pump (16) and by the small high-pressure pump (14) from a low-pressure region (13) into a high-pressure region (18). The high-pressure region (18) is connected to at least one injector (21). A control device (30) is provided, which can be used to conduct the entire pump output of the large high-pressure pump (16) or the small high-pressure pump (14) into the low-pressure region (13) via a discharge line (15).

Claims

1. A fuel-pumping device (1) for a fuel injection unit of an internal combustion engine, the fuel-pumping device comprising a large high-pressure pump (16) and a small high-pressure pump (14) which are arranged in parallel, the large high-pressure pump (16) and the small high-pressure pump (14) being configured to pump fuel from a low-pressure region (13) into a high-pressure region (18), the high-pressure region (18) being connected to at least one injector (21), further comprising a control unit (30) configured to control a total pump output of the large high-pressure pump (16) or the small high-pressure pump (14) into the low-pressure region (13) via a discharge line (15).

2. The fuel-pumping device (1) as claimed in claim 1, characterized in that a maximum pump output of the large high-pressure pump (16) is at least two times greater than a maximum pump output of the small high-pressure pump (14).

3. The fuel-pumping device (1) as claimed in claim 1, characterized in that the control unit (30) is a valve (33), which comprises two positions, so that in a first position, a connection between a discharge side of the large high-pressure pump (16) and the high-pressure region (18) and a connection between a discharge side of the small high-pressure pump (14) and the discharge line (15) is released, and in a second position, a connection between a discharge side of the small high-pressure pump (14) and the high-pressure region (18) and a connection between the discharge side of the large high-pressure pump (16) and the discharge line (15) is released.

4. The fuel-pumping device (1) as claimed in claim 1, characterized in that a discharge side of the large high-pressure pump (16) is connected either to the discharge line (15) or the high-pressure region (18) by means of the control unit (30).

5. The fuel-pumping device (1) as claimed in claim 4, characterized in that the small high-pressure pump (14) is always connected to the high-pressure region (18) by means of an ignition line (31).

6. The fuel-pumping device (1) as claimed in claim 4, characterized in that the control unit (30) is a valve (34), which comprises two positions, so that in a first position, a connection between the discharge side of the large high-pressure pump (16) and the high-pressure region (18) is released, and in a second position, a connection between the discharge side of the large high-pressure pump (16) and the discharge line (15) is released.

7. The fuel-pumping device (1) as claimed in claim 4, characterized in that the control unit (30) comprises a flush valve (41) which is arranged in the discharge line (15), the discharge line (15) being arranged between a non-return valve (42) and the large high-pressure pump (16) in a high-pressure connection (19).

8. The fuel-pumping device (1) as claimed in claim 1, characterized in that the small high-pressure pump (14) is mechanically coupled to the large high-pressure pump (16) such that the small high-pressure pump can be driven by means of said large high-pressure pump.

9. A method for pumping fuel in a fuel-pumping device (1) for a fuel injection unit of an internal combustion engine, the fuel-pumping device comprising a large high-pressure pump (16) and a small high-pressure pump (14) which are arranged in parallel, the large high-pressure pump (16) and the small high-pressure pump (14) being configured to pump fuel from a low-pressure region (13) into a high-pressure region (18), the method comprising, during gas operation of the fuel delivery device (1), pumping a total pump output of the large high-pressure pump (16) into the low-pressure region (13).

10. The fuel-pumping device (1) as claimed in claim 1, characterized in that a maximum pump output of the large high-pressure pump (16) is at least ten times greater than a maximum pump output of the small high-pressure pump (14).

11. The fuel pumping device as claimed in claim 3, where the valve (33) is a 4/2-way valve.

12. The fuel pumping device as claimed in claim 6, where the valve (34) is a 3/2-way valve.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Preferred exemplary embodiments of the invention are shown in the drawings and explained in greater detail in the following description.

(2) In said drawings:

(3) FIG. 1 is a schematic view of a fuel-pumping device of an internal combustion engine according to a first exemplary embodiment,

(4) FIG. 2 is a schematic view of a fuel-pumping device of an internal combustion engine according to a second exemplary embodiment, and

(5) FIG. 3 is a schematic view of a fuel-pumping device of an internal combustion engine according to a third exemplary embodiment.

DETAILED DESCRIPTION

(6) FIG. 1 shows a fuel injection unit of an internal combustion engine which comprises a fuel-pumping device 1. The fuel-pumping device 1 comprises at least one large high-pressure pump 16 and one small high-pressure pump 14, which are arranged in parallel. By means of the at least one large high-pressure pump 16 and the small high-pressure pump 14, fuel can be pumped into a high-pressure region 18 of the fuel injection unit.

(7) The high-pressure region 18 has for example a high-pressure accumulator. From the high-pressure region 18, one or more injectors 21 are supplied with fuel, at least one injector 21 being assigned to each cylinder of the internal combustion engine.

(8) A control unit 30 is arranged in the fuel-pumping device 1, which unit can control the total pump output of the large high-pressure pump 16 or the total pump output of the small high-pressure pump 14 by means of a discharge line 15 into the low-pressure region 13.

(9) The low-pressure region 13 has at least one delivery pump 10, which pumps fuel from a storage container 12 to the intake side of the large high-pressure pump 16 and to the intake side of the small high-pressure pump 14. Additional lines, valves and filters can also be arranged in the low-pressure region 13. Since the elements can be arranged in the low-pressure region 13 as desired, in the following, said region is referred to only as the low-pressure region 13.

(10) The fuel-pumping device pumps different amounts of fuel into the high-pressure region 18 according to the respective operating modes of a dual-fuel motor. If the dual-fuel motor is operated with liquid fuel (liquid fuel operation), then a large amount of liquid fuel must be pumped into the high-pressure region 18 and to the injector 21 by the fuel-pumping device 1. This is made possible by the operation of the large high-pressure pump 16, which has a greater maximum pumping volume than the small high-pressure pump 14.

(11) If the fuel-pumping device 1 is in liquid fuel operation, then the control unit 30 is controlled in such a way that the total pump output of the large high-pressure pump 16 is pumped into the high-pressure region 18, whereas the total pump output of the small high-pressure pump 14 is either controlled by means of the discharge line 15 or additionally pumped into the high-pressure region 18.

(12) If the dual-fuel motor is operated with gaseous fuel (gas operation), then only a small amount of liquid fuel has to be pumped by the fuel-pumping device 1 into the high-pressure region 18 and to the injector 21 to ignite the gaseous fuel. This small amount of fuel can be delivered to the injector 21 only by the small high-pressure pump 14.

(13) If the fuel-pumping device 1 is in gas operation, then the control unit 30 is controlled in such a way that the total pump output of the large high-pressure pump 16 is controlled by means of the discharge line 15 into the low-pressure region 30, whereas the total pump output of the small high-pressure pump 14 is pumped into the high-pressure region 18.

(14) The maximum pump output of the large high-pressure pump 16 is at least two times, preferably ten times, greater than the maximum pump output of the small high-pressure pump 14. In another embodiment, the maximum pump output of the large high-pressure pump 16 is at least twenty times greater than the maximum pump output of the small high-pressure pump 14.

(15) The above-mentioned arrangements and explanations are valid for all the following exemplary embodiments.

(16) According to a first exemplary embodiment, the control unit 30 is a first way valve 33, in particular a 4/2-way valve 33, which comprises two positions and an ignition line 31 which is connected to the intake side of the small high-pressure pump 14, and a pump line 32 which is connected to the intake side of the large high-pressure pump 16, connects to the discharge line 15 and a high-pressure line 19, which opens into the high-pressure region 18.

(17) In a first position of the first way valve 33, a connection between a discharge side of the large high-pressure pump 16 and the high-pressure region 18 and a connection between a discharge side of the small high-pressure pump 14 and the discharge line 15 is released. In the first position of the first way valve 33, the ignition line 31 and the discharge line 15 are interconnected, and the pump line 32 and the high-pressure line 19 are interconnected.

(18) In a second position of the first way valve 33, a connection between the discharge side of the small high-pressure pump 14 and the high-pressure region 18 and a connection between the discharge side of the large high-pressure pump 16 and the discharge line 15 is released. In the second position of the first way valve 33, the ignition line 31 and the high-pressure line 19 are interconnected, and the pump line 32 and the discharge line 15 are interconnected.

(19) FIG. 2 shows a second exemplary embodiment. The control unit 30 is a second way valve 34, in particular a 3/2-way valve 34, which comprises two positions and the pump line 32 which is connected to the intake side of the large high-pressure pump 16, connects either to the discharge line 15 or the high-pressure line 19, which opens into the high-pressure region 18.

(20) In a first position of the second way valve 34, a connection between the discharge side of the large high-pressure pump 16 and the high-pressure region 18 is released, and in a second position of the second way valve 34, a connection between the discharge side of the large high-pressure pump 16 and the discharge line 15 is released.

(21) In the first position of the second way valve 34, the pump line 32 and the high-pressure line 19 are interconnected, and in the second position of the second way valve 34, the pump line 32 and the discharge line 15 are interconnected.

(22) The discharge side of the small high-pressure pump 14 is always connected to the high-pressure region 18. An ignition line 31 connects the small high-pressure pump 14 to the high-pressure line 19, which opens into the high-pressure region 18.

(23) FIG. 3 shows a third exemplary embodiment. The control unit 30 comprises a flush valve 41 which is arranged in the discharge line 15. The flush valve 41 can be controlled pneumatically, electrically and hydraulically and opened or closed by means of a control unit (not shown in greater detail). The discharge line 15 branches off from a high-pressure connection 19 which connects the large high-pressure pump 16 to the high-pressure region 18 and is arranged between a non-return valve 42 and the large high-pressure pump 16.

(24) The non-return valve 42 opens the connection between the discharge side of the large high-pressure pump 16 and the high-pressure region 18 when a preset opening pressure on the side facing the large high-pressure pump 16 is exceeded. Said opening pressure can be built up by the large high-pressure pump 16 even with low pump outputs when the flush valve 41 is closed. A return flow of fuel from the high-pressure region 18 towards the large high-pressure pump 16 is not possible through the non-return valve 42.

(25) If the flush valve 41 is closed, then fuel is pumped into the high-pressure region 18 via the non-return valve 42 by the large high-pressure pump 16. If the flush valve 41 is open, then the total pump output of the large high-pressure pump 16 flows into the low-pressure region 13 via the discharge line 15. The pressure in front of the non-return valve 42 falls as soon as the large high-pressure pump 16 pumps into the low-pressure region 13, and therefore the non-return valve 42 closes.

(26) The discharge side of the small high-pressure pump 14 is always connected to the high-pressure region 18. An ignition line 31 connects the small high-pressure pump 14 to the high-pressure line 19 in a region upstream of the non-return valve 42, which opens into the high-pressure region 18.

(27) In another exemplary embodiment, the small high-pressure pump 14 can be in the form of an attachment on the large high-pressure pump 16 and can be driven by the large high-pressure pump 16. In this way, a mechanical interface for driving the small high-pressure pump 14 is omitted on the motor.