EP2895720A1

EP2895720A1 - Fuel system for an internal combustion engine which can be operated with at least two fuel types

Info

Publication number: EP2895720A1
Application number: EP12777896.7A
Authority: EP
Inventors: Alexander Gluschke; Frank Nitsche; Martin Maier; Winfried Langer; Peter Schenk; Thorsten Allgeier; Henri Barbier
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2011-12-16
Filing date: 2012-10-18
Publication date: 2015-07-22
Also published as: US20150285164A1; DE102011088795A1; CN103987944A; WO2013087263A1

Abstract

A fuel system (10) is proposed for an internal combustion engine (12) which can be operated with at least two fuel types (16, 40), wherein the fuel system (10) comprises an electrically driven high-pressure fuel pump (48) for at least one of the two fuel types (16, 40), which high-pressure fuel pump (48) is connected on the output side to a high-pressure line (30) which is common to the two fuel types (16, 40).

Description

description

title

Kraftstoffsvstem for an internal combustion engine, which can be operated with at least two types of fuel

State of the art

The invention relates to a fuel system according to the preamble of claim 1.

From the market are known internal combustion engines - in particular of

Motor vehicles - which can be operated alternatively and switchable with gasoline or LPG (liquefied petroleum gas). In order for a motor vehicle can be driven flexibly and environmentally friendly.

Disclosure of the invention

The problem underlying the invention is achieved by a fuel system according to claim 1. Advantageous developments are specified in subclaims. Features which are important for the invention can also be found in the following description and in the drawings, wherein the features, both alone and in different combinations, can be important for the invention, without being explicitly referred to again.

The invention has the advantage that a fuel system of a

Internal combustion engine can be operated with two types of fuel, filling losses can be avoided by means of a direct injection of LPG. Likewise, an unwanted power reduction can be avoided. A coking for example of injectors for the Gasoline direct injection can at least be reduced. Furthermore, the fuel system according to the invention allows a particularly good cold start capability. The injection system of the internal combustion engine can be produced in a particularly simple and cost-effective manner, with only one type of injection valves and only one high-pressure accumulator ("rail") being required. An electrically driven

High-pressure fuel pump may be located away from the internal combustion engine in or on a fuel tank (tank), whereby the

Temperature of the fuel pump low and a Vorforderdruck can be particularly low. The Vorforderdruck can easily by means of a

conventional electrically driven fuel pump can be generated. The

Temperature of the fuel in the tank can also be kept relatively low. The formation of gas bubbles and deposition of paraffin can be reduced or avoided and the life of the high-pressure fuel pump thus preserved. Furthermore, it allows that

Fuel system according to the invention to start the engine with LPG in a cold or hot state.

The invention relates to a fuel system for an internal combustion engine, which can be operated switchable with at least two types of fuel.

In particular, the fuel system comprises an electrically driven

High pressure fuel pump for at least one of the two types of fuel.

On the output side, the electrically driven high-pressure fuel pump is connected to a common for the two types of fuel high pressure line. Downstream of the high-pressure line, a high-pressure fuel accumulator for supplying injection valves of the internal combustion engine is connected. For the two types of fuel, the same injection valves are used, which also saves costs and the complexity of the internal combustion engine is reduced. In particular, the invention provides that a first fuel type gasoline or

Diesel fuel or other fuel having a comparatively low vapor pressure and a second fuel type is liquefied petroleum gas or other fuel having a comparatively high vapor pressure. This can do that

Fuel system are operated with the operation of the internal combustion engine particularly suitable fuels, which are available on the market almost nationwide. The invention works particularly well when the electrically driven

High-pressure fuel pump thermally insulated and / or from the

Internal combustion engine is arranged separately. This avoids that the high-pressure fuel pump is heated by the operating heat of the internal combustion engine. According to the comparatively small

Temperature increase of the fuel on the way from the fuel tank to the high-pressure fuel pump can be prevented even at relatively low hydraulic pressure evaporation or gas bubbles and thus disturbances in the operation of the fuel system can be avoided.

A first embodiment of the fuel system provides that it comprises a first mechanically driven high-pressure fuel pump for a delivery of gasoline and a second electrically driven high-pressure fuel pump for a delivery of LPG, which are connected on the output side to the common high-pressure line. As a result, essential elements of a conventional fuel system can be used, whereby the structure can be simplified. The mechanically driven high-pressure fuel pump includes, for example, a quantity control valve.

In addition, it is provided that in an area of a fuel tank for the respective type of fuel an electrically driven fuel pump is arranged, and that a pressure range of the electrically driven

Fuel pump for the delivery of gasoline is connected to a suction region of the mechanically driven high-pressure fuel pump, and that a pressure range of the electrically driven fuel pump for the promotion of liquid gas with a suction region of the electrically driven high-pressure fuel pump is connectable. Because of the invention low

Vorforderdrucks conventional electrically driven fuel pump can be used, which are preferably arranged in or on the respective tank. This saves costs.

In addition, it is provided that in a pressure range of the mechanically driven high-pressure fuel pump, a check valve is arranged, wherein the check valve can open in the conveying direction, and that in the

Pressure range of electrically driven fuel pump for the promotion of LPG a check valve or also a check valve is arranged. This prevents the two types of fuel from being mixed together. The check valve can also be designed as a switching valve.

A second embodiment of the fuel system provides that the electrically driven high-pressure fuel pump on the input side with both gasoline and liquid gas is connected and the output side is connected to the high pressure line. As a result, the mechanically driven high-pressure fuel pump can be saved and costs reduced.

In addition, it is provided that in an area of a fuel tank for the respective type of fuel, an electrically driven fuel pump is arranged, wherein a pressure range of the electrically driven

Fuel pump for the promotion of gasoline with a suction region of the electrically driven high-pressure fuel pump is connectable, and wherein a pressure range of the electrically driven fuel pump for the delivery of liquid gas is also connectable to the suction region of the electrically driven high-pressure fuel pump. Thus, inexpensive conventional electrically driven fuel pumps for generating the respective prefeed pressure can be used for the second embodiment of the invention.

In addition, it is provided that in the pressure range of the electrically driven fuel pump for the promotion of gasoline

Non-return valve is arranged, wherein the check valve can open in the conveying direction, and that in the pressure range of the electrically driven fuel pump for the production of LPG, a check valve or a check valve is arranged. This also prevents the two types of fuel from being mixed together. The check valve or the check valve can also be designed as a switching valve.

A third embodiment of the fuel system provides that in an area of a fuel tank for gasoline, an electrically driven fuel pump is arranged, and that the electrically driven high-pressure fuel pump is disposed in a region of a fuel tank for LPG, and that a pressure range of the electrically driven fuel pump with one Suction range of the electrically driven high-pressure fuel pump is connectable. This describes a particularly compact fuel system, which in many cases requires only two fuel pumps in total.

Optionally, in LPG operation to assist the electrically driven high pressure fuel pump, a prefeed pressure may be generated by means of an optional electrically driven fuel pump.

In addition, it is envisaged that in the pressure range of the electrically driven fuel pump for the production of gasoline

Check valve is arranged, wherein the check valve can open in the conveying direction, and that the fuel tank for LPG via a switching valve or a check valve is connected to the suction region of the electrically driven high-pressure fuel pump. This also prevents the two types of fuel from being mixed together. The switching valve or the check valve may be arranged upstream or downstream of the electrically driven high-pressure fuel pump.

Hereinafter, exemplary embodiments of the invention will be explained with reference to the drawings. In the drawing show:

1 shows a fuel system for an internal combustion engine in a first

Embodiment;

2 shows the fuel system for the internal combustion engine in a second

Embodiment;

3 shows the fuel system for the internal combustion engine in a third

Embodiment;

4 shows an injection device of the internal combustion engine in a first

Embodiment; and

Figure 5 shows the injection device of the internal combustion engine in a second

Embodiment. The same reference numerals are used for functionally equivalent elements and sizes in all figures, even in different embodiments.

FIG. 1 shows a simplified illustration of a fuel system 10 for an internal combustion engine 12 in a first embodiment. In a left upper portion in the drawing, a fuel tank 14 for a first fuel 16 is shown, which is present gasoline. On or in the

Fuel tank 14, a first electrically driven fuel pump 18 is arranged, which is the output side via a first low-pressure line 20 to the suction region of a mechanically (for example by means of a camshaft of the engine 12) driven high-pressure fuel pump 22 is hydraulically connected. At the first low-pressure line 20, a first pressure sensor 24 is arranged. The mechanically driven high pressure fuel pump 22 includes a quantity control valve (not shown) for controlling the amount of fuel delivered.

On the output side, the mechanically driven high-pressure fuel pump 22 is hydraulically connected via a first high pressure line 26 to a check valve 28. The check valve 28 may open in the conveying direction.

Downstream of the check valve 28, a second high-pressure line 30 is arranged, which is connected to a high-pressure fuel storage 32 ("rail"). At the high-pressure accumulator 32, a second pressure sensor 34 is arranged, by means of which a current fuel pressure in the

High-pressure accumulator 32 can be determined. The high-pressure accumulator 32 is via fuel lines with four injectors 36 of the present

Internal combustion engine 12 hydraulically connected.

In the lower left area in the drawing, a fuel tank 38 for a second fuel 40 is shown, which is liquid gas in the present case. At or in the fuel tank 38, a second electrically driven fuel pump 42 is arranged, which is the output side via a controllable check valve 44 and then via a second low pressure line 46 to the suction region of an electrically driven high-pressure fuel pump 48 is hydraulically connected. The electrically driven high-pressure fuel pump 48 is output side hydraulically connected via a third high pressure line 50 to the second high pressure line 30.

A dashed border 52 encloses those elements of the fuel system 10 which are conventional with respect to a conventional fuel system

Fuel 16 are additionally available. Alternatively, it is possible to integrate the electrically driven high-pressure fuel pump 48 in addition to the electrically driven fuel pump 42 in the fuel tank 38.

In a first mode, the internal combustion engine 12 is operated with gasoline. For this purpose, the first electrically driven fuel pump 18 delivers gasoline from the fuel tank 14 into the first low-pressure line 20, wherein a hydraulic pressure of the gasoline is increased to a first delivery pressure-for example up to 10 bar. The first delivery pressure is by means of the first

Pressure sensor 24 determined. The quantity control valve (not shown) controls the supply to the mechanically driven high pressure fuel pump 22

Fuel quantity. The mechanically driven high-pressure fuel pump 22 delivers the gasoline at a second delivery pressure into the first high-pressure line 26, wherein the following check valve 28 opens. For example, the second delivery pressure is up to 150 bar. Thus, gasoline is in the second

High-pressure line 30 and then promoted in the high-pressure accumulator 32. The second electrically driven fuel pump 42 and the electrically driven high pressure fuel pump 48 do not work and the check valve 44 is locked.

In a second mode, the internal combustion engine 12 is operated with LPG. For this purpose, the second electrically driven fuel pump 42 delivers liquid gas from the fuel tank 38 through the now open

Lock valve 44 in the second low pressure line 46, wherein a hydraulic pressure of the liquid gas is increased to a first discharge pressure. The fuel pressure in the second fuel tank 38 is for example up to 21 bar. The electrically driven high-pressure fuel pump 48 delivers the liquid gas at a second delivery pressure into the third high-pressure line 50 and then into the high-pressure accumulator 32. For example, the second delivery pressure is up to 70 bar. The first electrically driven fuel pump 18 and the mechanical driven high pressure fuel pump 22 do not promote. The check valve 28 locks, so that a mixing of the two types of fuel 16 and 40 upstream of the check valve 28 is not carried out. A flow rate of the liquefied gas is controlled according to a respective demand of the engine 12 by controlling an electric power of the second electrically driven fuel pump 42 and / or the high pressure electrically driven fuel pump 48. In particular, the second electrically driven fuel pump 42 and the electrically driven high pressure fuel pump 48 are separate from the

Internal combustion engine 12 is arranged, resulting in a thermal insulation of the internal combustion engine 12. Together with a sufficiently high first and second delivery pressure is achieved that a vapor pressure of the

Liquefied gas or gasoline in the fuel system 10 is not exceeded. Thus, the LPG remains on the way from the fuel tank

38 to the injection by means of the injection valves 36 in a liquid state.

FIG. 2 shows a further simplified illustration of the fuel system 10 for the internal combustion engine 12 in a second embodiment. In the upper left in the drawing area, the fuel tank 14 for the first fuel 16 (gasoline) is again shown. At or in the fuel tank 14, the first electrically driven fuel pump 18 is arranged, which gasoline - for example, with a delivery pressure of up to 10 bar - in the first

Low pressure line 20 promotes. The first low pressure line 20 is connected in the figure 2 with a check valve 28 which can open in the conveying direction. Downstream, the check valve 28 is hydraulically connected to the suction region of the electrically driven high-pressure fuel pump 48, which promotes fuel via the second high-pressure line 30 into the high-pressure accumulator 32.

In the lower left area in the drawing, in turn, the fuel tank 38 for the second fuel 40 (LPG) is shown. On or in the

Fuel tank 38, the second electrically driven fuel pump 42 is arranged, which on the output side also has the check valve 44. A delivery pressure of the second electrically driven fuel pump 42 is for example up to 21 bar. Downstream, the check valve 44 is at the second Low-pressure line 46 connected, which is also hydraulically connected to the suction of the electrically driven high-pressure fuel pump 48. The electrically driven high pressure fuel pump 48 delivers the gasoline via the second high pressure line 30 into the high pressure accumulator 32. The dashed line 52 in turn encloses those elements of the fuel system 10 that are complementary to a conventional single fuel type fuel system 16 are.

In the first mode (gasoline) of the internal combustion engine 12, the second electrically driven fuel pump 42 is turned off and the check valve 44 is locked. The first electrically driven fuel pump 18 and the electrically driven high-pressure fuel pump 48 promote, wherein the check valve 28 opens. The delivery pressure is for example up to 70 bar.

In the second mode (LPG) of the internal combustion engine 12, the first electrically driven fuel pump 18 is turned off, the

Check valve 28 locks. The check valve 44 is open and the second electrically driven fuel pump 42 and the electrically driven high-pressure fuel pump 48 promote. The delivery pressure is also, for example, up to 70 bar.

During operation of the fuel system 10, similar to the fuel system 10 of FIG. 1, the respective delivery pressure ensures that the vapor pressure of the liquefied gas or of the gasoline in the fuel system 10 is not undershot. In addition, the electrically driven high-pressure fuel pump 48 is designed so that even during or after a switch from

Liquefied gas operation on the gasoline operation always sufficient compression takes place, which prevents the formation of any vapor bubbles. As in the fuel system 10 according to FIG. 1, the electrically driven fuel pumps 18 and 42 and the electrically driven high-pressure fuel pump 48 are arranged separately from the internal combustion engine 12 in FIG. Thus, the respective fuel until the injection by means of the injection valves 36 remains sufficiently cold. Furthermore, the electrically driven high pressure fuel pump 48 allows sufficient Fuel pressure in the high-pressure accumulator 32 is already present before or during the start of the internal combustion engine 12 and thus no gas bubbles.

FIG. 3 shows a further simplified illustration of the fuel system 10 for the internal combustion engine 12 in a third embodiment. In the in the

Drawing upper left area, in turn, the fuel tank 14 for the first fuel 16 (gasoline) is shown. At or in the fuel tank 14, the first electrically driven fuel pump 18 is arranged, which gasoline - for example, with a pressure of up to 10 bar - in the first

Low pressure line 20 promotes. In FIG. 3, the first low-pressure line 20 is connected to a check valve 28, which can open in the conveying direction and in the present case is arranged on or in the second fuel tank 38. The fuel pressure in the second fuel tank 38 is for example up to 21 bar.

In addition, the electrically driven high-pressure fuel pump 48 and a switching valve 58 are arranged on or in the second fuel tank 38 of Figure 3. On the input side, the switching valve 58 is connected to the stored liquid gas and the output side, it is connected to the suction region of the electrically driven high-pressure fuel pump 48. Likewise, the check valve 28 is connected downstream to the suction area of the electrically driven high-pressure fuel pump 48. The electrically driven high-pressure fuel pump 48 conveys the respective fuel via the second high-pressure line 30 into the high-pressure accumulator 32. The delivery pressure is in both the gasoline mode and in the LPG mode

for example, up to 70 bar. The dashed border 52 in turn encloses those elements of the fuel system 10 which are complementary to a conventional single-fuel 16 fuel system.

In addition, between a suction region of the electrically driven

High pressure fuel pump 48 and the fuel tank 14, a hydraulic connection 68 ("gasoline return line") arranged. In case of gasoline operation of the internal combustion engine 12, any gas bubbles may be flushed out via the hydraulic connection 68, so that the gas bubbles are not conveyed by the electrically driven high-pressure fuel pump 48. In the first mode of operation of the internal combustion engine 12, gasoline by means of the first electrically driven fuel pump 18 from the first

Fuel tank 14 via the first low-pressure line 20 to the

Promoted check valve 28, whereby this opens. The electric

High-pressure driven fuel pump 48 increases the hydraulic pressure of the gasoline up to 70 bar, wherein the gasoline is conveyed via the high-pressure line 30 into the high-pressure accumulator 32. The switching valve 58 is closed, so that mixing of the two types of fuel does not take place.

In the second mode of operation of the internal combustion engine 12, LPG is supplied from the second fuel tank 38 via the opened switching valve 58 from the electrically driven high pressure fuel pump 48 to the high pressure line 30 and further to the high pressure accumulator 32. The first electrically driven fuel pump 18 is turned off, whereby the check valve 28 locks. As a result, there is no mixing of the two types of fuel.

Optionally, in the fuel system 10 of FIG. 3, one or the second electrically driven fuel pump 42 can be arranged in the fuel tank 38, which delivers liquid gas from the second fuel tank 38 to the input of the switching valve 58 at a first delivery pressure. The second electrically driven fuel pump 42 is shown in phantom in the drawing.

FIG. 4 shows an injection device of the internal combustion engine 12 in a first embodiment. Shown is a LPG intake manifold injection in

Combined with a gasoline direct injection. The internal combustion engine 12 has four cylinders 60 in the present case. Inlet valves (not shown) are connected to intake manifolds 62 which can draw in air from an air system (also not shown). The high pressure accumulator 32 is with first

Injectors 64 connected, which can inject fuel directly into the cylinder 60. Furthermore, the high pressure accumulator 32 is second

Injectors 36 are connected, which can inject fuel into the suction pipes 62. The vertical dashed lines are electrical control lines (not numbered). If the internal combustion engine 12 is operated with gasoline, the gasoline is injected directly into the cylinder 60 by means of the injection valves 64. The second injection valves 36 are blocked. If the internal combustion engine 12 is operated with liquefied petroleum gas, the liquefied gas is injected into the intake pipes 62 by means of the injectors 36. The first injectors 64 are locked.

FIG. 5 shows, as an alternative to FIG. 4, the injection device of FIG

Internal combustion engine 12 in a second embodiment. Shown is a LPG intake manifold injection in combination with a gasoline intake manifold injection. In contrast to FIG. 4, the embodiment according to FIG. 5 has no first injection valves 64. For both types of fuel, the respective fuel by means of the second injection valves 36 in the

Suction pipes 62 injected.

Claims

claims

1 . Fuel system (10) for an internal combustion engine (12), which with

at least two types of fuel (16, 40) can be operated, characterized in that the fuel system (10) is an electrically driven high-pressure fuel pump (48) for at least one of the two

Fuel types (16, 40) includes, which is the output side connected to a common for the two types of fuel (16, 40) high pressure line (30).

2. Fuel system (10) according to claim 1, characterized in that a first fuel (16) gasoline or diesel fuel or other fuel with a comparatively low vapor pressure and a second fuel (40) is liquefied petroleum gas or other fuel with a relatively high vapor pressure ,

3. Fuel system (10) according to claim 1 or 2, characterized in that the electrically driven high-pressure fuel pump (48) is thermally insulated and / or separated from the internal combustion engine (12).

4. Fuel system (10) according to claim 2 or 3, characterized in that it comprises a first mechanically driven high-pressure fuel pump (22) for a delivery of gasoline and a second electrically driven high-pressure fuel pump (48) for a delivery of LPG, which are connected on the output side to the common high-pressure line (30).

5. Fuel system (10) according to claim 4, characterized in that in an area of a fuel tank (14, 38) for the respective fuel (16, 40) an electrically driven fuel pump (18, 42) is arranged, and that a pressure range of electrically driven fuel pump (18) for the supply of gasoline is connected to a suction region of the mechanically driven high-pressure fuel pump (22), and that a Pressure range of the electrically driven fuel pump (42) for the promotion of LPG with a suction region of the electric

driven high-pressure fuel pump (48) is connectable.

Fuel system (10) according to claim 5, characterized in that in a pressure range of the mechanically driven high pressure fuel pump (22) a check valve (28) is arranged, wherein the check valve (28) can open in the conveying direction, and that in the pressure range of the electric driven fuel pump (42) for the promotion of LPG a check valve (44) or a check valve is arranged.

Fuel system (10) according to claim 2 or 3, characterized in that the electrically driven high-pressure fuel pump (48) on the input side with both gasoline and liquid gas can be connected and the output side is connected to the high-pressure line (30).

Fuel system (10) according to claim 7, characterized in that in an area of a fuel tank (14, 38) for the respective fuel (16, 40) an electrically driven fuel pump (18, 42) is arranged, wherein a pressure range of the electrically driven fuel pump (18) for the delivery of gasoline with a suction region of the electrically driven high-pressure fuel pump (48) is connectable, and wherein a pressure range of the electrically driven fuel pump (42) for the production of LPG also with the suction region of the electrically driven high-pressure fuel pump ( 48) is connectable.

Fuel system (10) according to claim 8, characterized in that in the pressure range of the electrically driven fuel pump (18) for the production of gas a check valve (28) is arranged, wherein the check valve (28) can open in the conveying direction, and that in the Pressure range of the electrically driven fuel pump (42) for the promotion of LPG a check valve (44) or a check valve is arranged.

10. Fuel system (10) according to claim 7, characterized in that in an area of a fuel tank (14) for gasoline, an electrically driven fuel pump (18) is arranged, and that the electrically driven high-pressure fuel pump (48) in a region of a fuel tank (38) is arranged for liquefied gas, and that a

Pressure range of the electrically driven fuel pump (18) with a suction region of the electrically driven high-pressure fuel pump (48) is connectable.

1 1. Fuel system (10) according to claim 10, characterized in that in the pressure range of the electrically driven fuel pump (18) for the promotion of gasoline, a check valve (28) is arranged, wherein the check valve (28) can open in the conveying direction, and that the

Fuel tank (38) for LPG via a switching valve (58) or a check valve with the suction of the electrically driven high-pressure fuel pump (48) is connected.