DE10146051A1 - Common-rail fuel injection system for IC engine has petrol or diesel fuel line combined with liquefied petroleum line - Google Patents

Abstract

The fuel injection system has petrol or diesel fuel line (10) combined with a liquefied petroleum gas line (11) in front of the high pressure fuel pump (5) of the fuel injection system, for allowing bivalent direct injection of the petrol or diesel fuel or liquefied petroleum gas.. A freely selected quantity of petrol or diesel fuel can be mixed with the liquefied petroleum gas in the liquefied petroleum gas tank, for providing a required fuel mixture.

Description

State of the art

The invention describes a direct fuel injection system, in particular common rail Direct injection system for the direct injection of liquid gas (LPG) or other liquid Fuels in the combustion chamber of an internal combustion engine.

Liquefied petroleum gas, also known as LPG (liquified petroleum gas) or LPG, is a pro pan-butane mixture with mixture proportions that differ from region to region due to storage under relatively low overpressure (approx. 7-8 bar at room temperature) in is in liquid form in the fuel tank (for this reason further with "medium pressure fuel ", in contrast to those at room temperature and atmospheres pressure liquid fuels ["low pressure fuels"], such as petrol, diesel or the like), but is gaseous at atmospheric pressure.

In the previously known systems for supplying rivers available on the market siggas in the combustion chamber of an internal combustion engine, the liquefied gas is pressed out of the spe target, pressure-resistant liquid gas tank (blow-off overpressure of the pressure safety valve: 30 bar) through its own excess pressure, liquid into an evaporator pressure regulator, where it, through Redu adornment of the excess pressure and with the addition of thermal energy to compensate for the ver evaporative cooling, converted from the liquid to the gaseous state and in this gas shaped physical state was supplied to the intake manifold of the engine. Either indicated sucks through the negative pressure of the combustion air flowing in the intake tract or through, Active injection controlled by a regulation in front of the intake valves of the internal combustion engine ne.

The feed represents the current state of the art in the supply of liquid gas tion of the liquid gas in the intake tract in the liquid state, with a pump in conn the constant pressure of the liquid phase upstream of the injectors with a pressure regulator guaranteed. (http: / / www.gas-autogasanlagen.de/Autogasanlagen/autogasanlage.html and http: / / www.autogastechnik.de/technik.html). (EP 0 725 208 B1)

State of the art in the supply of gasoline or diesel or the like, atmospä pressure and room temperature liquid fuels (here further in Abgren referred to liquid gas as "low pressure fuel") is direct injection, at which the fuel at high pressure directly into the combustion chamber of the internal combustion engine is sprayed, with stratified charge at partial load. ("Innovations for safe, clean and economical driving [components, modules, systems] ", information brochure of the company Bosch with the number 1 987 485-ZVW2-0100-D, page 4-8). Their technology is knows and is therefore not explained further here. However, direct injection engines can with the previously used fuel supply configurations not as direct injection System operated with liquefied petroleum gas because they have the necessary operating pressures and Fuel temperatures at the high pressure pump inlet were not reached.

For the bivalent operation of internal combustion engines with petrol or diesel or similar, in Combined with liquefied petroleum gas, there has been a separate fuel supply for each fuel system used. This has a relatively high construction cost.

Furthermore, the injection of liquefied gas upstream of the inlet valves still leads to displacement supply of intake air through the evaporating fuel gas and thus to reduce it the mixture mass available for combustion.

In addition, with the injection of fuel before the intake valves, no operation with ge stratified charge possible.  

Advantages of the invention

These problems are solved by the features listed in the claims, in that the present invention causes

• a) liquid gas is also injected directly into the combustion chamber of an internal combustion engine can and that
• b) by merging the gasoline and LPG lines before the high injection system pressure pump, with a single injection system optionally both Low pressure fuels (petrol or diesel or similar), as well as medium pressure fuel (LPG = LPG = liquefied petroleum gas) or a mixture of both can be injected directly into the combustion chamber of an internal combustion engine.

The advantages of the invention

• a) LPG is a product that automa in the production of gasoline or diesel table. Its use thus increases the utilization of the crude oil.
• b) compared to systems with direct petrol injection:
  • 1. the higher energy density (approx. 2%) of the LPG-air mixture increases the performance
  • 2. The higher octane number of LPG and the better internal mixture cooling allow higher compression, which in turn increases efficiency, torque and performance even at full load.
  • 3. The raw emissions of polluting pollutants are reduced, particularly during cold starts, because the fuel-air mixture does not need to be enriched.
  • 4. CO2 emissions are reduced by up to 20%
  • 5. Since LPG contains practically no sulfur, exhaust gas cleaning is simplified
  • 6. Harmful toxic emissions of Pak, aldehydes, benzene, toluene are reduced
  • 7. no groundwater hazard from LPG, since it is not water-soluble
  • 8. The service life of the engine and spark plugs is extended by the reduction of aggressive acids and carbon deposits and less dilution of the lubricating oil
• c) Compared to liquid gas systems with intake manifold injection:
  • 1. Reduced fuel consumption through direct injection. In the European driving cycle (NEDC), the saving compared to engines with conventional injection processes is 15-20% fuel. Added to this is the fuel saving through the complete filling of the cylinders with combustion air, so that fuel savings of up to 30% are possible.
  • 2. no second injection system is required and also no additional control function for the medium-pressure fuel, as described in EP 0 725 208 B1.

drawings

Embodiments of the invention are shown in simplified form in the drawings and in the following description explains.

In the drawings Fig. 1, the system areas of the fuel injection, Fig. 2 is a monovalent version of the fuel direct injection system for medium-pressure fuel flues petroleum gas in the variant with two fuel return lines from the high pressure region, which return the unused fuel in the tank, Fig. 3 is a monovalent imple mentation of the direct fuel injection system for the medium-pressure fuel liquid gas in the variant with the fuel return to the fuel supply line in front of the high-pressure pump, Fig. 4 shows a bivalent variant for medium-pressure and low-pressure fuels. This variant is characterized by two fuel return lines in the low pressure system, which end in the low pressure fuel tank. Fig. 5 also shows a bivalent embodiment. It differs in the arrangement of high pressure pump and high pressure regulator in the high pressure part from the variant shown in Fig. 4. In addition, it has only one fuel return line, which also does not end in the tank, but opens into the fuel supply line in front of the high pressure pump.

Description of the embodiments

The invention is based on internal combustion engines commercially available with a direct injection system for low pressure fuels. For this reason, in Fig. 1 only that, with these internal combustion engines, the principle interaction of the system areas fuel supply A (consisting of a medium-pressure fuel supply A1 or a medium-pressure fuel supply A1 and a low-pressure fuel supply A2), high-pressure part B, the electronic control C and the periphery D shown and dispensed with the further explanation of the areas B, C and D, since one of the advantages of the invention described here is that it is not necessary to intervene in these areas for direct injection in order to inject liquid gas directly.

In Fig. 2 is a monovalent version of the fuel direct injection system is shown in which the low-pressure fuel system A2 is replaced by a medium-pressure fuel system A1. From a medium-pressure-resistant fuel tank 10 (blow-off pressure 30 bar), which is filled via a filling line 11 , 3 liquid gas 18 presses into the supply line 12 after opening the solenoid valve, flows through the fuel cooler 14 and then arrives at the input of the medium pressure pump 4 . The fuel pump 4 increases the pressure of the liquid gas 18 and, together with the low-pressure pressure regulator 6, ensures that the liquid gas 18 reaches the input of the high-pressure pump 5 in the liquid state. This presses the liquefied gas with a pressure increased by the fuel density factor (density of low-pressure fuel to density of liquefied gas) into the combustion chamber of the internal combustion engine, regulated by the electronic control C. Unused, excess fuel is returned to the liquefied gas tank 10 via the return lines 16 and 19 .

Fig. 3 also shows a monovalent version of the liquid gas direct injection but with a different configuration of the high pressure part B. Here, the rail 7 and high pressure regulator 8 are connected to each other and the excess fuel is not here in the fuel tank, but in front of the high pressure pump 5 back into the supply line guided.

Fig. 4 explains the hydraulic circuit diagram of a direct fuel injection system according to claim 7-24 with a short circuit 13 branching from the common fuel supply line 20 and two separate fuel return lines 16 to the low-pressure fuel tank.

The medium-pressure fuel system A1 is shown with a feed line 1 from the low-pressure fuel tank (not shown), which leads to a high-pressure fuel pump 5 . The high-pressure fuel line leads to the high-pressure fuel regulator 8 via the fuel rail (common rail) 7 . Both from the high pressure regulator 8 and the high pressure fuel pump 5 leads a fuel return line 16 back into the low pressure fuel tank.

At the low pressure fuel line 1 , the supply line for the liquid gas is connected with a T-piece, which comes from the pressure tank 10 for the liquid gas. By Magnetven tile 3 in combination with check valves 2 ensures that fuel flows to the high-pressure pump 5 from only one of the two fuel tanks and the liquid gas with its higher pressure level does not press into the low-pressure fuel tank.

The second fuel pump 9 in this line is used for a brief pressure increase in the low-pressure fuel system in the phase of switching from the liquid gas mode to the low-pressure fuel mode. Without this second fuel pump 9 , after switching off the medium-pressure fuel pump 4, the pressure level in the fuel supply lines 1 and 20 would drop to the pressure level of the low-pressure circuit, i.e. below the pressure that prevents the liquefied gas from evaporating. However, there are liquid gas residues in the injection system at the time of switching and also for a while afterwards, which are prevented from evaporating by the increased pressure. The increased pressure is maintained in the low-pressure operating mode by the second low-pressure fuel pump 9 until all of the liquid gas in the entire line system has been replaced by low-pressure fuel.

The fuel pump 4 increases the pressure of the liquid gas during operation in the liquid gas mode and thereby ensures that the liquid gas, even when heated, reaches the HD pump 5 in the liquid state. The same purpose serves a fuel cooler 14 which is attached to the fuel pump 4 . If the fuel temperature exceeds a critical value (approx. 30 ° C), then the cooling process is started via the temperature sensor 17, in which cooling is caused by an evaporating medium, either by the refrigerant of the cooling circuit of the air conditioning system or a branched part of liquefied petroleum gas 18 . The variant with branched liquid gas 18 is shown , which is then fed to the intake system of the engine via the circuit for evaporated low-pressure fuel.

The additional fuel pump 9 also opens up the possibility of pumping low-pressure fuel into the liquefied petroleum gas tank via a further branch line 13 , which opens into the return line 16 and together with it is fed into the filling line 11 for the liquefied gas, thereby creating a low-pressure fuel-liquefied gas mixture with a freely selectable mixture shares can be generated. The admixture of low-pressure fuel to the liquefied gas prevents possible lubrication problems in the system. This process is controlled by a separately switchable solenoid valve 15 .

The pressure control valve 6 ensures constant pressure at the input of the high-pressure fuel pump 5 even in the medium-pressure operating mode.

From the fuel supply line 20 branches off in front of the high-pressure pump 5, a control line 22 which pressurizes the control piston of the high-pressure regulator 8 during operation with liquid gas, which pressure is added to the existing spring tension and thereby generates the necessary higher injection pressure in the liquid gas mode.

In the liquid gas operating mode, the excess liquid gas is fed via the return line for the medium pressure fuel 19 into the liquid gas filling line 11 and from there back into the liquid gas tank 10 . Check valves 2 prevent the liquid gas 18 from flowing out . The invention has advantages on several levels. Because the liquid gas is now injected directly and liquid into the combustion chamber, it no longer displaces intake air. This increases the degree of filling of the cylinders compared to injection into the intake tract and thus also the performance of the engine. At the same time, all advantages of the direct injection process are retained. The second level of advantage is the structural simplification of the liquid gas system. Gas-air mixers, evaporator pressure regulators and separate injection nozzles for the liquid gas are no longer required. A separate measurement and control system for the liquefied petroleum gas is unnecessary, since the existing system for the low-pressure fuel can be used for both fuels due to the liquid aggregate state of both fuels.

Fig. 5 also shows a bivalent version of the direct fuel injection but with a different configuration of the high pressure part B. Here, the rail 7 and high pressure regulator 8 are connected to each other and the excess fuel is not here via the fuel return line 16 in the fuel tank, but in front of the high pressure pump 5 again fed back into the feed line 20 .

A fuel tank for liquid gas 10 is shown , from which a fuel line 12 leads away and a direct injection system B, consisting of a high pressure pump 5 , a distributor pipe 7 with high pressure lines 21 leading to high pressure injection valves, and a pressure control valve 8 , from which a fuel return line 16 in front of the high pressure pump in the common fuel supply line 20 opens.

The object is achieved in that the lines 1 and 12 , which connect the tanks of the two types of fuel with the direct injection system B, are brought together in a common line 20 before the high pressure pump 5 . A magnetic valve 3 in combination with a check valve 2 in the supply lines 1 and 12 ensures that only one of the two fuels can flow to the high-pressure pump 5 and the liquid gas 18 with its higher pressure level does not press into the low-pressure fuel tank. A fuel pump 4 increases the pressure of the liquid gas and thus ensures that the liquid gas 18 , even when heated, reaches the high-pressure pump 5 in the liquid state.

The same purpose is served by a fuel cooler 14 which is installed in front of the fuel pump 4 in the line 12 . If the fuel temperature exceeds a critical value (approx. 30 ° C), then the cooling process is started via the temperature sensor 17, in which cooling system is caused by an evaporating medium, either refrigerant of the cooling circuit of the air conditioning system or a branched-off part of liquid gas 18 . The variant with the connection to the air conditioning circuit is shown.

In order to compensate for the lower density of this fuel compared to gasoline in a bivalent gasoline-LPG system in operation with liquid gas, the high-pressure pump 5 must have a larger volume of liquid gas 18 for the same amount of combustion air compared to e.g. B. Inject gasoline into the combustion chambers. This is done by increasing the injection pressure corresponding to the reciprocal densities, controlled by the pressure control valve 8 .

List of reference numbers

1

Low-pressure fuel line

2

check valve

3

magnetic valve

4

Medium-pressure fuel supply fuel pump (LPG system)

5

high pressure pump

6

Low-pressure regulator

7

Fuel rail (common rail)

8th

High pressure regulator

9

2. Low pressure fuel supply fuel pump

10

Pressure resistant tank for medium pressure fuel (LPG)

11

Filling line of the medium pressure fuel supply

12

Supply line for the medium pressure fuel

13

Short line

14

Fuel cooler

15

Solenoid valve in the short circuit line

16

Return line for the low pressure fuel

1

17

Temperature sensor for the medium pressure fuel temperature

18

Liquefied petroleum gas (LPG)

19

Return line for the medium pressure fuel

20

Common fuel line

21

Solenoid valve for the coolant supply

22

control line

Claims (24)

1. Direct fuel injection system for internal combustion engines with a fuel supply A, consisting of a low-pressure part A2 and a medium-pressure part A1, a high-pressure part B, an electronic control C, and periphery D (z. B. turbocharger or exhaust gas recirculation), characterized in that the fuel supply A , including fuel tank 10 , medium pressure resistant (PN = 30 bar max.). This can be done by cutting ring fittings of the fuel line connections and medium-pressure-resistant fuel hoses with medium-pressure-tight screw connections or other suitable medium-pressure-resistant connection systems. 2. Direct fuel injection system, according to claim 1, characterized in that liquid gas 18 , also referred to as LPG (LPG = liquefied petroleum gas = propane-butane gas mixture with different percentages), as a fuel in liquid aggre gas state directly into the combustion chamber of the internal combustion engine is injected. 3. Direct fuel injection system according to claim 2, characterized in that the fuel can be cooled controllably by a cooling device 14 before entering the high pressure part B. 4. Direct fuel injection system according to claims 1-3, characterized, that the temperature of the LPG represents the switch-on and switch-off variable for the cooling control. 5. Direct fuel injection system according to claim 1-4, characterized in that the cooling device 14 is cooled by evaporating refrigerant of an air conditioning system or a small amount of branched, evaporating liquid gas. 6. Direct fuel injection system according to claim 5, characterized, that the LPG vapor analogous to the fuel vapors of petrol the intake system stem of the internal combustion engine is supplied. 7. Direct fuel injection system according to claims 1-6, characterized in that in addition a low-pressure fuel supply A2 including low-pressure fuel tank and fuel pump, before the high-pressure part B with the fuel lines of the medium-pressure system A1 is pressure-tightly connected, so that with a single injection system B and the associated injection control C both Liquefied petroleum gas 18 (medium pressure fuel) as well as fuels that are liquid at atmospheric pressure and room temperature (low pressure fuels, e.g. gasoline, diesel or the like) can be directly and liquid injected into the combustion chamber of the internal combustion engine. (Bivalent direct fuel injection system). 8. Direct fuel injection system according to claims 1-7, characterized in that the low-pressure fuel supply A2 and the medium-pressure fuel supply A1 are locked against each other by electrically switchable solenoid valves 3 and check valves 2 . 9. Direct fuel injection system according to claims 1-8, characterized in that, to compensate for the different fuel densities, the injection pressures generated by the high-pressure pump 5 , controlled by the high-pressure control valve 8 , are changed reciprocally to the fuel densities and reciprocally to the air consumption figures of the two fuels. (Accordingly, the pressure increase factor for petrol and LPG fuels is 1.32 when operating in LPG mode compared to the injection pressure in petrol mode). 10. Direct fuel injection system according to claims 1-9, characterized in that the control of the high pressure control valve 8 to change the injection pressure hy drastically, by branching fuel pressure from the fuel supply 20 who can realize the. 11. Direct fuel injection system according to claims 1-10, characterized in that, by appropriate electrical connection of the solenoid valves 3 , between the never derdruckstoff and the medium pressure fuel can be freely selected. 12. Direct fuel injection system according to claim 1-11, characterized in that when switching from operation in the medium pressure mode to the low pressure mode to the low pressure pump, a second fuel pump 9 is switched on for a short time. 13. Direct fuel injection system according to claim 1-12, characterized in that this second fuel pump 9 is connected in series in the low-pressure fuel circuit A2 with the first fuel pump of this circuit, so that their pressures add up. 14. Direct fuel injection system according to claim 1-13, characterized, that the pressures that the two fuel pumps generate together over the evaporator pressure of propane. 15. Direct fuel injection system according to claim 1-14, characterized in that this second low-pressure fuel pump 9 is placed before the merging of the low-pressure fuel circuit A2 with the medium-pressure fuel circuit A1. 16. Direct fuel injection system according to claim 1-15, characterized in that after switching on the fuel pump (s) of the low-pressure fuel supply A2, the fuel pump 4 of the medium-pressure fuel supply A1 is switched off. 17. Direct fuel injection system according to claim 1-15, characterized in that during the phase in which the second fuel pump 9 of the low pressure fuel supply A2 is switched on, the solenoid valves 3 of the return lines 16 to the low pressure tank are kept closed. 18. Direct fuel injection system according to claim 1-17, characterized in that the solenoid valves 3 , which seal off the return lines 16 to the low-pressure tank, are opened at the earliest when 10 low-pressure fuel is present at the input of the medium-pressure fuel tank. 19. Direct fuel injection system according to claim 1-18, characterized in that a measuring device, from the resulting discontinuous fuel volume flow change when changing the fuel type generates a control signal which simultaneously opens the solenoid valves 3 in the return lines 16 to the low pressure tank and the shutdown of the second Fuel pump 9 controls the low pressure fuel supply A2 at this time. 20. Direct fuel injection system according to claim 1-19, characterized in that when switching from operation in low pressure mode to medium pressure mode, the fuel pump 4 of the medium pressure fuel supply A1 - and the fuel pump located in the low pressure fuel tank is switched off. 21. Direct fuel injection system according to claim 1-20, characterized, that, instead of two series-connected electric fuel pumps, one mechanically driven fuel pump the functions of the two electric fuel pumps in the Low pressure fuel system takes over. 22. Direct fuel injection system according to claim 1-21, characterized in that a fuel line 13 branches off from the fuel inlet of the low-pressure system A2 upstream of the high-pressure pump 5 , which is coupled pressure-tight to the liquid gas fill line 11 or the return line 16 for the medium-pressure fuel. 23. Direct fuel injection system according to claims 1-22, characterized in that the short-circuit line 13 according to claim 22 can be opened and closed by a solenoid valve 15 . 24. Direct fuel injection system according to claim 23, characterized in that it makes it possible to mix the medium pressure fuel LPG 18 with low pressure fuel.